8.8 Gear Install

a corral original article
Chris Neighbors

From the factory most Mustangs are usually equipped with 2.73 rear gears. A specially ordered Mustang could be had with 3.08 gears and up to 3.27 gears for automatic transmission, or 1999 and later cars. While Ford's choice of gearing may have helped reach CAFÉ standards, it does little to satisfy the speed freak in all of us.

One of the many things to consider before journeying into a gear swap is the differential. Is your stock traction-lok allowing the creation of some monstrous "one-wheel peels"? Are you considering an aftermarket differential, or upgrading to a 31-spline traction-lok? This is an ideal time to address these issues, unless you crave the smell of friction modifier and "can't get enough"...

Please take the time to read through the pinion depth set-up section. There are several methods to set-up the pinion, ranging from expensive tooling to questionable technique. Decide which method suits your particular needs and circumstances, including risk associated with each. (I would suggest that if it's a first time install, buy a Ford Motorsport gearset; they seem to have good quality control, and can relieve some installation frustration...)

The sources:

There are many gear vendors, but I'll try and highlight a few that are notable...

Vendor

Phone

Fax

Website

Ford Motorsport

     

D&D Performance

(248) 926-6220

   

National Drivetrain

(800) 507-4327

(773) 376-9135

http://www.natldrivetrain.com

Precision Gear

(734) 946-0524

   

Ratech

(513) 742-2111

   

Personally, I try and buy most of my parts from Summit; they usually have what I want priced competitively, but there are many reputable vendors for parts...

Required tools: (well, maybe not all required; some merely desired...)

  • Two sets of jackstands (or substitute ramps for one set; if you're real fortunate, use a lift!)
  • Floorjack (two-ton works great!)
  • Metric combination wrench set (at least 12mm 12-point, 13mm, 15mm)
  • Metric sockets and ratchet (same sizes as above...)
  • SAE sockets and ratchet
  • 1/2" drive break-over bar
  • Impact wrench
  • Impact sockets: 3/4", 1-1/16"
  • Foot-pound torque wrench, 1/2" drive
  • Inch-pound torque wrench, beam style
  • Transmission plugs (or old yoke)
  • Drain pan(s)
  • Punch or letter stamp set
  • 6" or 8" calipers, digital or dial
  • 1" travel dial indicator
  • Magnetic base and stand for dial indicator
  • Two-jaw puller (6" works fine...) (three-jaw for flange; two-jaw required for bearing removal...)
  • Parts washer or many cans of carb cleaner!
  • Air compressor and air nozzle
  • Regular screwdrivers (large and small)
  • Valco Tube-Grip (RTV sealant dispenser; the best $15 I ever spent!)
  • 3/8" or 1/2" diameter punch (I use Chevrolet fuel pump pushrod)
  • Dremel w/ cut-off wheel (for marking driveshaft to flange orientation)
  • Hammer: dead-blow, sledge (small one!), or regular carpenter's
  • 3" diameter slug of material, approximately 1-1/2" thick or so...(pinion seal installer)
  • Bearing separator, large
  • Shop press, or access to one (you may need it several times...)
  • Pinion depth gauge tooling
  • Depth micrometer, 0-6" range

Required chemicals:

  • RTV (I prefer Permatex UltraBlack, but any oil resistant RTV will work.)
  • Loc-tite 242 (blue, removable)
  • Penetrating oil (Kroil, Tri-Flow, WD-40, etc.)
  • Two quarts of your favorite gear oil
  • Anti-seize
  • Carburetor or brake cleaner (I prefer Wal-Mart Tech2000 carb cleaner)
  • Gear marking compound (available through Summit, or in some Ratech kits...)

The Teardown:

Select a suitable spot that won't impede normal foot traffic and can be occupied for a couple of days without disturbing. Jack the car up as high as safely possible and support with jackstands (double check stability before crawling under!). I usually support the rear by the subframe connectors; I let the rear down to full shock extension. This gives me quite a bit of room to work on the set-up...Remove the rear wheels and tires, and set aside. Remove the rear sway bar, using 15mm tools (four fasteners) (SN95 note: slide the ABS cables from the ABS brackets, located on the aft (rear) sway bar fasteners; then remove fasteners). With a 1/2" socket and ratchet, remove the three bottom fasteners on the rear cover. Place a drain pan under the cover, and loosen the seven remaining fasteners. Starting from the bottom up, continue to loosen the fasteners and pry out on the bottom of the cover with a large flat-bladed screwdriver, to drain the oil. Once the majority of the oil is drained, remove the fasteners and cover. (Drain plug? Now might be a good time to install one in the cover, if you're so inclined. They make transmission drain plugs that should fit the bill, otherwise, weld in a pipe bung and install a plug. While this won't allow you to drain all of the oil, it'll get most of it out. Ease of service would be improved greatly!) With the Dremel (or suitable marker), mark the orientation of the driveshaft relative to the pinion flange. Spray some penetrating oil on the exposed ends of the driveshaft fasteners, and let set for a few minutes. With the 12-point 12mm wrench, and the dead-blow hammer, break the fasteners loose and remove (you have to rotate the driveshaft to get two fasteners out at a time...). If the shaft hasn't been out for some time (or ever!), you may have to tap the u-joint carrier to get it to break loose from the flange. Place another drain pain under the tailshaft of the trans, remove the driveshaft (depending on the oil level in the trans, you may drain out a pint or so...Some oil will also be present in the yoke.), and install a trans plug to keep from creating a slick. Remove the pinion shaft lock fastener with a 5/16" wrench or socket (it's fairly tight), while holding the differential from turning by inserting a large screwdriver into the ring gear fasteners or holding one fastener with a combination wrench. Once the fastener is out, push or drive the pinion shaft out. Remove the brake drums and push the axles inward, to unseat the C-clips on the axle end; push the clips out with a screwdriver.

SN95 axle removal instructions:

With the advent of rear discs and ABS on the SN95 units, some special steps must be followed to remove the axles. Start off by removing the caliper fasteners with a 13mm tool (two per side), and remove the caliper. The caliper mounting bracket is held to the axle with two 15mm headed fasteners per side; use a break-over bar to break these loose, then remove brackets (you might install the mounting and caliper fasteners in their original parts to keep them in order...). Remove the discs and set aside. I think somebody at Ford was having a bad day in the design department regarding the ABS reluctor (exciter) and pick-up. The pick-up is located 90 degrees relative to the "wheel", pressed into the backing plate from the backside. While this doesn't sound bad, the

the "wheel" contacts the housing of the pick-up BEFORE the C-clip is unseated. Again, not too bad, but if Ford had put a small relief in the reluctor, in one spot, you could get the axles out without too much hassle. As it is, you have to remove the pick-up fastener (positive (male) Torx-style head; use a 6-point 1/4" socket to remove...), and try to move the pick-up back about an 1/8". Not much, but it's a real pain to move if it has any build-up or corrosion, as the pick-up is located inboard of the axle flange. Without an access hole, you have to tap the pick-up at an angle to get it to move back...Not a good day at corporate design, IMHO! With any luck, you'll get it without destroying anything...If you do (like I did, LOL!), it's off to Pep Boys or Ford for a replacement, at $52 to $75, respectively.

Once the C-clips are pushed off the axle ends, carefully slide the axles out, taking care not to nick or damage the axle seals. Inspect the axles for bearing damage: the wheel bearing rollers ride directly on the axle (as opposed to in a cup), and can score the axle if improperly lubed or contaminated. If you find axle damage, offset bearings are available to allow you to use the existing axles. I usually set the axles in the wheel so that they are upright; seems a decent way to store the loose parts in an already limited workspace...

With the axles out, attention can now turn to the differential assembly. Mark the caps for proper reassembly; use "L" and/or "R", or any other scheme that you can remember (bottom line: don't mix the caps up! They are machined like engine main caps, so be careful.). Prior to removing the diff assembly, check the backlash [Backlash: The clearance between a pinion tooth and the adjacent ring gear teeth. It is the total movement allowed between contacting teeth.] for reference. Set the dial indicator and magnetic base up so that the tip is perpendicular to a ring gear tooth. Measure and record the backlash: should be in the .008"-.015" range. With a 3/4" socket and break-over bar, loosen the cap fasteners about four or five revolutions, but do not remove yet. The differential assembly may need to be "persuaded" to unseat it from the housing; use a rubber hammer, dead-blow, pry bar, wrench, or a large screwdriver inserted into the ring gear bolts to break it loose (the two units I've done so far have come loose by hand). Once the assembly is loose, remove the caps and set aside. Carefully pull the differential assembly from the housing, while simultaneously grabbing and containing the shims and bearing races on each side. Measure the thickness of the shims and record relative to location, and keep races in order.

Differential disassembly: With the differential on the bench, use a 3/4" impact socket and wrench to remove the ten (10) fasteners that hold the ring gear to the differential case. Once all fasteners are removed, tap the ring gear off of the case with a soft hammer, alternating blows around the circumference. If you are planning to rebuild the traction-lok, remove the S-spring (carefully!) by driving it out (away from you) with a hammer and punch. Rotate the pinion gears (the small ones) around to the openings in the case, and remove (If you have set the axles up vertically in a wheel, it makes an excellent tool for holding one side gear and rotating the differential). The side gears and frictions/steels should all fall out; try and keep them in order, relative to installation side.

Traction-lok rebuild:

A brief traction-lok description: The t-lok, IMHO, is a very simple yet effective method of torque transmission. It uses a combination of frictions and steels; the steels spline to the O.D. of the side gears (the I.D. is splined to accept the axles), and the frictions keyed to the differential case (driven by the ring gear) with tangs. An S-spring is used to provide initial clamping load, then is supplemented by the outward forces created and transmitted by the pinion gears.

If you plan to rebuild the traction-lok, it is advisable that you do it now, for a couple of reasons: 1. Going to a numerically higher gear ratio, the pinion diameter goes down, and the ring gear thickness goes up. What does this really mean? The S-spring "gap" between the side gears is partially blocked (straight line of sight) by the thicker ring gear (you can still get the spring in, it's just a bit tougher). 2. Without the ring gear, you can support the differential case by the flats (across the clutch cavity) on a block of wood, while driving the S-spring in place. Also, there are two approaches to component order: the factory method, and the alternating method. From the factory, t-lok's are packed in this order: shim, friction, steel, steel, friction, steel, steel, friction, side gear. The alternating pack is as described: shim, friction, steel, friction, steel, friction, steel, friction, side gear. There is some debate on the durability of the alternating method, as you have reduced the number of splined components (thereby increasing shear and contact stresses), while increasing the ability to transmit torque. My contention? I've never seen a rearend go out due to t-lok spline failure; it's usually axle related (OK, at some point the axles become stronger than the steel splines; at which point, I don't know! Maybe somebody ought to "run some numbers"...). Both methods work: satisfy your particular needs and plan accordingly (I prefer and suggest the alternating method, FWIW.). The F5AZ-4947-BA kit will allow you to accomplish the "factory" set-up; for the alternating, you can buy a pack of frictions (see number below), or reuse two (one for each side) of your best existing frictions.

The rebuild: Soak the frictions in gear oil for a minimum of fifteen (15) minutes (while you clean the diff case, gears, and shims) prior to assembly in order to avoid dry working and possible component damage. Be forewarned: the clutches will still pop when first driven (I about had a conniption when I first rolled mine out of the garage after gears and t-lok! The thing popped about a dozen times in turns before settling out. I soaked mine about twenty (20) minutes, but the last set I worked on was soaked for about two hours. Result: only one or two mild pops, even with alternating frictions and a new F-150 S-spring!). With the differential case on one bearing, install the .045" thick shim in the bottom cavity. Apply a few drops of gear oil to the other .045" shim and place in the upper cavity (the oil will hold it in place, as long as the drops are towards the case...). Stack the frictions, steels, and side gear (engaging steels) in the lower cavity per your packing choice, then stack the upper units on the side gear, and install as a unit (make sure tangs locate in case). Install one of the pinion gears in place, and, while holding inward with one thumb, install the opposite side pinion gear 180 degrees apart (I prep the pinion gears first by putting a couple drops of gear oil between the gear and it's steel bearing "shell"). Pick up the whole assembly, and install on the end of an upright axle. Rotate the diff case while holding the pinions inward as hard as possible; if you're lucky, the "assembly" will roll right into place. If the shims are too thick, the pinion gears will not clear the case (acting like a built in gauge...). Change one shim to the next thinnest, and try again. If it fails to go together, change the other shim to the next thinnest: repeat until the gears rotate into position. It's fine to have one shim .005" thicker than the other; just don't end up with a .010" disparity. If the pinion gears line up, and the shaft will go through, you have it correct (It took me about three tries the first time.).

S-spring installation: This is actually the most trying part of the whole procedure! The S-spring, by design, has to be compressed to allow installation. The Ford (Helm) manual directs you to tap it into place with a rubber hammer; maybe one that weighed about 1000 pounds and was frozen rock hard! More people have had difficulty with this one seemingly simple task, and I'm no exception. I fought my first one for about an hour, then finally got it by compressing it in a vise, holding it compressed with a couple of pairs of needle-nose Vise-grips, and driving it into place. Shortly thereafter, Larry Turvy from the Corral offered a great tip: use two, 2" capacity worm-type hose clamps. Larry's original suggestion was to use the clamps to compress the spring, but I still use the vise, then install the clamps, leaving a bit of the end exposed to get the thing started. Place the compressed spring into position, and start driving it into place with a hammer. With all luck, the spring will start in a few blows. Continue driving the spring in, until you stop on one of the "worm" portions of the clamp. Cut this clamp out with aviation or tin snips (Dremel or hacksaw may work), and continue driving, removing the other clamp when required. (Note: I found a 6-8" long piece of 1" x 1-1/2" rectangular tube, used as a "punch", to be very helpful in "persuading" the S-spring into position, especially when using the F-150 unit!). Be careful not to drive the spring all the way through and out the back; sight down the pinhole and roughly center the spring. Set the unit aside for the time being.

Congratulations! You've just completed the Traction-lok rebuild!

Pinion depth set-up:

There are several methods to establish pinion depth: a couple of correct ways, and a few questionable. Please read through the sections below, and decide which is best for you. Keep in mind, all but "the good" require pinion depth readings of your existing set-up prior to disassembly. However, it's always a good idea to get some reference numbers, check the existing set-up for accuracy, and try your hand at proper tooling set-up and reading.

If you have the factory gears in place, and are in good condition (i.e. no noise, whining, clunking, etc.), you have a perfect target dimension to start from (after all, Ford should have set it up with one of their gauges, LOL!). If not, the "master housing dimension" of 4.4199" should be used. This is the theoretical depth from the axle centerline to the back side of the pinion head. If you do not have a "good" reference set installed, you'll need to do little careful measuring and math (based on set-up procedure) to establish the proper target dimension, or use the OTC tooling.

The good: The best method for establishing proper pinion depth for an FMS gearset is to use the pinion depth gauge, part number T79P-4020-A. OTC makes this tool for Ford, and I understand it to be quite costly; somewhere in the neighborhood of $600 (complete; I've heard the essentials are about $250.)! Unfortunately, it is as it's described: a gauge. You cannot read an actual pinion depth number; you install the gauge and slide one shim at a time (better have a stack of them!) until you feel drag. That shim will set the pinion depth properly. If you have access to a machine shop, and are inclined to build your own, I have details of the depth gauge (AutoCAD drawings).

So what if you have Richmond, or another set that dictates an optimum pinion depth measurement (scribed on pinion normally)? The OTC gauge is completely useless in that situation; you need a depth checking tool. Essentially, it's a jig that locates off the diff case bearing bores, is squared up somehow, and projects to allow you to read a number (see the Chambers site for a good picture). I have no idea of cost or availability of these units: if anybody finds some details, please forward them (of course you'll get credit!

The bad: Shortly after I did my first set of gears (on my car, BTW) using the NPDM (see "the ugly" below), I thought, "there has to be an easier way to check pinion depth". What I cooked up is an aluminum plate, 1" thick (thickness isn't a major concern, as long as you know/measure the "actual"), that will bolt to the housing using the differential cap fastener locations. Bolt the plate to the housing using four 1/ 2"-13 socket head fasteners, and torque to 20-30 lb-ft or so. See the drawing at right:

For FMS gears: Using a depth micrometer, insert the plunger through the hole at the bottom of the plate. Hold the mic firmly to the base, and touch the pinion face. Record the depth, rotate the pinion, and take another reading. Measure and record several locations on the pinion to get a good average (Dpavg). This is the target pinion depth for your new FMS pinion.

For non-FMS gears: Using a depth micrometer, you touch off the bearing bore (Dbb) and record a number. Then, touch off the pinion in several spots while rotating the pinion, record, and average (Dpavg). Measure the diameter of the bearing race (Dbr; Timken specs lists LM603012 cup diameter as 3.0625"), and record. The pinion depth will be the average pinion depth minus the bearing bore depth, plus one half of the bearing race diameter (PD = Dpavg - Dbb + (Dbr / 2)).

The ugly: The "Neighbors pinion depth master" (NPDM), or combination square for short. After fretting for several days about pinion depth (and little to no help tracking any information down what-so-ever), it dawned on me one night: the gauge doesn't really do anything, other than provide a reference point. Aha! I was on to something...Once I realized this, that reference point can be anywhere, provided it doesn't move relative to the pinion. Axle centerline, the bumper cover, your next door neighbor's fence...as long as it's a repeatable measurement. I took the rule out of my combination square, and attached it to the "short" square side of the body with two small C-clamps (this makes an "L", with the "long" square side and one edge of the scale on the same plane). I then clamped this contraption to the axle cover mount surface (nice, flat, machined surface), using two spring clamps, locating the "rule" portion approximately over the pinion centerline (make note of the initial location, as you will want to install the NPDM in the same position during pinion installation). Using calipers (I used digital, but dial works also), measure the depth to the pinion by holding the end of the calipers square on the edge of the scale, and slide the calipers out, making sure it contacts the face of the scale (this gets you on a parallel axis with the pinion centerline). Drop the depth part of the caliper down until it contacts the pinion (on a flat area, not in the letters!). Record several measurements while rotating the pinion, and average. Now you have a benchmark...

Once you decide the pinion depth obtainment method, take all pertinent measurements (I like to get pinion bearing pre-load also), then remove the pinion assembly. Attach a pinion retaining tool with two driveshaft fasteners (if the car is jacked up to the right height, the end of the angle will rest on the concrete, allowing "hands free" operation), as illustrated right, or use two fasteners and a long pry bar. Unless you need the exercise, use a 1-1/16" impact socket and wrench to remove the pinion nut. The factory minimum torque is 140 foot-pounds, so it will take some effort to break loose. Remove the pinion flange with a two or three-jaw puller (I tried my harmonic balancer puller initially, but it didn't work for two reasons: 1. The driveshaft fasteners are bigger than the "slots" in the puller, and 2. The proximity of the flange to the housing precludes the use of long, smaller bolts with a nut...). The pinion should fall loose from the front bearing, but if it doesn't, a little "persuasion" with a hammer will do the trick. The front pinion bearing and slinger will remain in the housing, captured by the pinion seal. Remove the seal by driving a regular screwdriver under the lip (between the lip and the housing), and pry out; grab the bearing and slinger as you do.

Clean all the loose parts with carb, brake, or parts cleaner, keeping in order. Set aside and let dry, or blow off with compressed air. Pull out as much oil as you can by hand from the bottom of the housing, scooping it out and into the drain pan. Get the oil out of the axle tubes by jacking up one side (at a time) of the housing slightly (to get the oil to run downhill...) and spraying with cleaner (I also stuffed a couple of paper towels in and pushed through with a broom handle). Blow the housing and tubes out with compressed air.

Bearings and things:

Pinion bearing removal
Differential case bearing removal
Differential case bearing installation
Inspect all bearings and races for signs of scoring, fretting, galling, and/or spalling; replace as required. IMHO, as cheap as bearings are, it's good insurance to replace them (if you have the tooling to do it) while you're doing the swap. See "Service parts" for applicable part numbers and referenced prices. Below are some of the photos illustrating bearing removal/installation.

Pinion bearing, rear:

Remove: press, bearing separator, two pieces of 4" channel (~ 6" long)

Install: press, old bearing race and a 6" piece of 2-1/2" square tubing (or pipe)

The pinion bearing is best suited to be removed/installed on a press, requiring a separator to get the bearing off. I shopped for quite a while to find a bearing separator locally (I waited too long and needed one that day, LOL!). If you don't have a press and a separator, cart the pieces down to your local machine/mechanic shop and let them handle the work. Anti-seize the pinion prior to pressing the bearing on, and don't forget the pinion shim!

Differential case bearings:

Remove: 6-8" capacity two-jaw puller, large impact socket, bolt (drops inside socket), impact

Install: press, old bearing race

The differential case bearings can be difficult to remove. The case doesn't have a relief under the bearing to allow the installation of a separator, so you're limited to a two jaw puller. Also, you have to create a surface to pull against. I wound up using a large impact socket, whose O.D. was slightly smaller than the bearing I.D., and a hex head bolt that fit inside the socket; a surface that the puller would press against. I lubed the threads of the puller with oil, and used the impact to remove the bearings. Have somebody watch/hold the "legs" as you do; they tend to spread a bit...

Pinion gear mock-up:

Remove the bearing from the old pinion using a press and bearing separator, as illustrated above. Remove the shim from the pinion; measure and record the thickness. The nominal shim thickness used on an FMS gearset is .030", but can vary +/- .002". If you are installing FMS gears, look closely at the new pinion; it may be marked with a +2, +1, 0, -1, -2. If so, that "number" is added to .030" (e.g +2 would indicate the use of a .032" thick shim; likewise, the -2 would require .028") to obtain the proper shim thickness for that gearset. Regardless of the marking on pinion (which is an expeditious method of getting close to correct pinion depth), the final result should always be checked with proper tooling and marking compound.

Install the correct (or old) shim on the new pinion, apply anti-seize to the bearing area, and press the rear bearing onto the pinion, making sure it is seated. Insert the pinion "assembly" into the housing, and install the front bearing and slinger (without a crush sleeve for the mock-up). Apply anti-seize to the flange splines and the pinion nut threads, and install the flange and old pinion nut. Tighten the nut until you achieve the proper bearing pre-load torque (16-29 in-lbs new, 8-14 in-lbs old: Note: this is not the torque on the nut. It is the torque reading generated while rotating the flange/pinion assembly.). Assemble the pinion depth tooling in/on the housing, and check the pinion depth as described previously. Compare the number achieved to the "target" number (or that engraved on the face of the pinion, plus tooling thicknesses). Disassemble the mock-up, adjust the shim thickness as required, and repeat the mock-up procedure until the correct pinion depth is established.

If you have the ring differential assembled, install it per the instructions below. Check and correct the backlash and run-out, then apply marking compound and check contact pattern. This will save some effort in the event that the pinion depth is slightly off and needs adjustment, even though target depth was achieved.

And now for a little assembly:

After the proper bearing shim and bearing are pressed onto the pinion, place the new crush sleeve on the assembly. Place the front bearing and oil slinger into the housing. Apply a thin coat of RTV to the pinion seal and install (the bearing and slinger will NOT fit through seal after installation! The diff case bearing race makes a good seal installer.). Install the pinion assembly, crush sleeve, flange and new nut, using anti-seize on the threads and splines. Now comes the muscle part (or brains, if you have air tools)! Retain the flange with the tool used during removal (angle or ?), and the tighten the nut until the flange contacts the crush sleeve. The minimum torque to collapse the crush sleeve is 140 ft-lbs; it will take quite a bit of horsepower to get this sucker to collapse! Wiggle the pinion assembly as you tighten the nut to get an idea of how much more you need to collapse sleeve. When you feel very little play, sneak up on the tightening (watch a reference mark on the socket; stop at 1/16" to 1/8" linear movement along the circumference) and check the bearing pre-load torque often to get 16-29 in-lbs (new) or 8-14 (old) (new bearings have higher torque than old; once ran, they will loosen up slightly). DO NOT exceed the pre-load torque, and DO NOT back the nut off to reduce torque (this keeps the bearings loaded). If you exceed the torque, you'll have to get new crush sleeve and try again. Just take your time and sneak up on it...

Ring gear connects to the, diff case:

In order to insure proper ring gear to differential case seating, the backside of the ring gear should be sanded/scuffed to eliminate any burrs that might create a high spot. I used a D/A (dual action sander for autobody) with some 180 grit to make short work of it (3M makes some great Scotch-brite pads that chuck in a drill; they should do fine!). The ring gear is designed and machined to produce a slight interference between the I.D. of the ring and the differential case. To ease assembly, place the ring in the oven (just don't get caught, LOL!), at or about 200 degrees Fahrenheit for fifteen to twenty minutes. The heat will cause the ring to expand, allowing easier installation. Once heated, install the ring gear, tapping into position slightly w/ hammer, noting alignment of fasteners (or, build some alignment pins by cutting the heads off of a few fasteners and grinding a slight taper on the ends: 7/16"-20 x 1-1/2" to 2" long ought to work.). Once aligned, use five fasteners to suck the ring gear up flush with the face of the case. Put a drop of blue, removable Loc-tite on the remaining five fasteners and install. Remove the initial set of five, and apply Loc-tite. Once all fasteners are Loc-tited and in place, torque them in stages (25, 50, final 70-85 ft-lbs), alternating fasteners (since there are ten fasteners, I torqued five in a star pattern to 25 ft-lbs as I do a wheel, then next pattern. Proceed in stages.). Some suggest deburring the teeth lightly, but to date I have not done it; if you're inclined, do so carefully...

Diff assembly into housing:

With the side specific bearing races and shims, reinstall the assembly into housing (you did keep sorted out, right?). Install the caps in the correct locations and positions (arrows on the caps point outwards), and torque the fasteners to 70-85 ft-lbs. Check gear backlash with a dial indicator and magnetic base; it should be .008-.015". If out of this range, you'll need to get shims to move the differential assembly either toward or away from pinion to correct. The Ford service manual has a good table of shims and resultant change in backlash (You'll need a copy of this to ascertain the thickness change to produce the desired backlash change, as it's not a linear function.). Essentially, what you remove from one side will have to be added to the opposite side. Once backlash is within range, remove the shims and install .006" thicker shims on both sides. You'll have to drive these in; they keep the bearings loaded (Hint: Place the thinner shims in place first, then drive the thickest into position last). Check the ring gear run-out on the back face. This should be no more than .004". If it's more, then remove the diff assembly, rotate the ring gear relative to the case, reassemble, retorque, reinstall, recheck. Redo as required (I think I'm REtarded!). Once proper backlash and run-out are obtained, check the gear contact pattern using gear marking compound. Paint four to six teeth in three or four locations around the ring gear, and "drive" the diff assembly several revolutions by rotating the pinion (try and keep some friction on the diff assembly as you do). Check the pattern against the chart at right (or look at the Drive Train Page site listed). Adjust as required to obtain the desired contact pattern. Install the axles, c-clips, pinion shaft and fastener (torque shaft lock pin to 15-30 ft-lbs). Apply an 1/8" bead of RTV to the cover and install; add oil, install swaybar, tires, etc.

Break-in period:

As with most highly stressed components, a break-in period is recommended to maximize part life; gears are no exception. While the "procedure" may differ between manufacturers, the "method" is the same. A semi-civil jaunt is taken to bring the gearset to operating temperature, and allowed to cool (stone cold); repeat as prescribed by the manufacturer (at most three times), prior to staging a burnout or wheelie contest, LOL!

Miscellaneous tidbits:

Speedometer gears:

An important consideration during the gear swap is finding the right drive/driven speedometer gears per your application. Ford used a seven (7) tooth drive gear in the 1983 to 1989 T-5's, then switched to an eight (8) tooth drive in 1990 (used through 1995). If you have 3.73's with an eight-tooth drive, and the highest driven gear with twenty-three (23) teeth, the speedometer still reads 5% fast. With the limited number of gears available, the combinations are (number in the table is the driven gear tooth number to be used with left hand gear ratio and drive gear column):

Rear end ratio / Speedo drive

Six (6) tooth drive

Seven (7) tooth drive

Eight (8) tooth drive

3.27

16

19

21

3.55

17

20

23

3.73

18

21

n/a

4.10

20

23

n/a

4.30

21

n/a

n/a

Part number

E3ZZ-17285-B

E3ZZ-17285-A

F0ZZ-17285-A

Color

Black

Yellow

Green

Note: The above combinations are based on tires with or very near to stock diameter (225/55-16 is 25.74").

Optional "equipment":

  • Rear girdle:Mac, TFS, T/A
  • 28 or 31-spline axles (4 to 5 lug, hardened, etc....):FMS, Moser
  • Aftermarket differential:Auburn, PowerTrax, Lock-Rite
  • Hardened, longer studs (to allow the use of open ended lug nuts on aftermarket wheels...)
  • C-clip eliminators (or 9" ends: see William Mathis' Mustang Performance Handbook, Volume II )

Ring and Pinion/installation/rebuild kits:

Ford Motorsport: The Motorsport gears, from all that I've heard and gathered, seem to be the best in terms of noise (or lack thereof) and ease of assembly. It has been said that you can install FMS gears without doing any set-up or checking, by using the existing pinion shim and differential case bearings (a practice I don't recommend, by the way; at least check them!). When you order an FMS set, you get ring and pinion, crush sleeve, and a pinion nut; I presume the manufacturers way of implying their close product control by lack of instructions...

Motive Gear: Motive offers an economical method to increase the car's gear, without decreasing your wallet too much. Motive gears are made in Italy, and as with most of the products I've seen from Italy (ranging from aluminum wheels to high-speed automated manufacturing equipment), the quality and value are exceptional. The gears are lapped as sets from the factory, and they dictate the optimum pinion depth. When you receive the gears, you get:

  • Ring and pinion gear
  • Crush collar
  • Pinion nut
  • Pinion shims (one each):.010, .011, .012, .013, .014, .015, .017, .018, .019, .020, .021, .022, .023
  • Instruction sheet

Ratech: Ratech packages and offers at least three levels of installation kits, available through Summit. Kits are dubbed "standard", "complete", and "deluxe", in order of increasing parts and cost ($43, $90, $110 respectively).
The standard (105K, $43) includes:

  • Rear cover gasket
  • Pinion shims (.010", .012" (3), .020")
  • Crush sleeve
  • Pinion seal
  • Pinion nut
  • Differential case shims (backlash: .010" (4), .012" (4), .015" (2), .020" (4), .094" (4))
  • Ring gear fasteners

The complete (305K, $90) adds:

  • Differential case bearings (2)
  • Pinion bearings (front and rear)
  • Small tub of gear marking compound

Finally, the deluxe (3008K, $110) adds:

  • Axle bearings (2)
  • Axle seals

Traction-lok: Ford parts houses offer a fairly complete kit that allows the rebuild of stock traction-lok type units. If you go "shopping" request part number F5AZ-4947-BA (was $61.50, more now); good for both 28 and 31-spline units. It includes:

  • 4 ounce bottle of friction modifier - C8AZ-19B546-A
  • Six (6) frictions plates - F5AZ-4947-AA (includes 3-F's and 4-S's)
  • Eight (8) steel plages - F5AZ-4947-AA (includes 3-F's and 4-S's)
  • Shims (2 each): .025", .030", .035", .040", .045" - E0AZ-4A324-G, H, , C, D, F (respectively)
  • Pinion shaft lock bolt - D8BZ-4241-B

Service parts: (if you didn't buy rebuild kits)

Pinion bearing, rear:
  • Bearing: M802048-N Koyo
  • Race: M802011-N Koyo
  • Bearing set: M802048 Koyo ($15.69)
Pinion bearing, front:
  • Bearing: M88048-N Koyo
  • Race M88010-N Koyo
  • Bearing set: M88048 Koyo ($7.99)
  • Pinion seal: 3604 (National) ($5.29)

Differential case bearings:

  • Bearing: LM603049 Timken
  • Race: LM603012 Timken
  • Bearing set: A36 (or just 36) Timken ($9.99)
  • Rear wheel bearings: 5707 Timken ($12.99)
  • Rear wheel seal: 8660S (National) ($1.49)
  • S-springs: (sorry about the "sloppy" drawing; original layout was lost!)
  • Mustang: E0AZ-4214-A ($11.99)
  • F-150: F3TZ-4214-A ($11.99)

    Torque/set-up specifications:

    Torque

    SAE

    SI

    Tool size

    Pinion bearing pre-load, used

    8-14 lb-in

    .9-1.6 N-m

    n/a

    Pinion bearing pre-load, new

    16-29 lb-in

    1.8-3.2 N-m

    n/a

    Pinion nut, minimum

    140 lb-ft

    190 N-m

    1-1/16"

    Ring gear fasteners

    70-85 lb-ft (in stages)

    95-115 N-m

    3/4"

    Main bearing fasteners

    70-85 lb-ft

    95-115 N-m

    3/4"

    Pinion shaft lock bolt

    15-30 lb-ft

    20-41 N-m

    5/16"

    (Metal) Cover fasteners

    25-35 lb-ft

    34-47 N-m

    1/2"

    Driveshaft

    70-95 lb-ft

    95-130 N-m

    12mm 12-point

    Lugnuts

    85-105 lb-ft

    115-142 N-m

    Set-up

    Backlash

    .008"-.015"

    .203-.400 mm

    Ring gear runout

    .004" maximum

    .0762 mm

    References:

    1991 Shop Manual. Helm Publishing

    Part #:FPS-12193-91 (last two digits = year)

    Cost:$52

    Phone:(313) 865-3418

    "All backed up." by Vinnie Kung

    Muscle Mustang & Fast Fords ; June 1999, 92...107

    Sites of interest:

    The Drive Train Page: http://www.thegrid.net/thedrivetrainpage/diff.htm

    5.0 Mailing List Archives: http://www.netwiz/50ml/archives/

    (prompts for search; try pinion, gear, etc.; scroll through)

    The World of Chambers: http://www.kellnet.com/chambers/

    (pick "gearset install" off of sidebar...)

    Innovative Performance Solutions:http://www.ipschassis.com/gear/ford8.htm

    West Coast Differentials:http://www.differentials.com/njinstall.htm

    Randy's Ring & Pinion:http://www.ring-pinion.com

    PowerHouse (tools and such):http://www.powerhouseproducts.com

     

    The "Big thanks!" list:

    Paul Rebold: for keeping me straight and supplying the detailed and great information on the Ford (well, OTC actually) pinion depth gauge.

    Larry Turvy: for coming up with the "two-clamp" s-spring installation procedure. I'm sure he's saved people countless hours of pain and suffering with this tidbit...

    Craig Adkins: for getting me started by answering my questions regarding traction-lok rebuild. His personal attention to my questions encouraged me to help others...

    Fraser Elliott: the first "sucker" that I tried to help! Frasier later wrote the first set of T-lok instructions...At one time, MFE, Craig A. and I were dubbed "the T-lok three-stooges"; we'd barrage whoever posted questions!

    Glenn Forester: a master ASE certified mechanic and instructor, Glenn has probably forgotten more than most of us will know!

     

     


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