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41 Posts
Discussion Starter #1
I have a 98 and i'm wanting a shift kit.....I've got a local tranny man who does good work give me a real good price on the transgo kit installed.....$150 for everything....can't beat that....I was wondering if the transgo kit is bad for the 98's....I have heard some bad things on the newer cars.....anybody had any problems with the 98 and back....????????? Please Post......Thanks a bunch guys

100 Posts
i think the jerry mod (trans101 article) found on the website is much better for the 4R70W trans.

you'll bark second everytime. its like a drug.

get a large trans cooler to go with this

if you have a chip with the right tune, you'll leverage the trans mods above even more.

just ask people about the jerry mod, they'll tell you.

28 Posts
I had a transgo in my old Tbird (which had the 4r70w). I have heard the Jerry Mod is better, but I loved the Transgo, and like the guy I bought my tranny from (who put the kit in, along with a stall, and a 4th gear servo), Transgo has been around for a long time, and they probably know what they are doing.
As far as luck, I loved my transgo shift kit, and had no problems

175 Posts
the transgo shift kit on my '01 GT was the best mod i have done for my is very reliable and actually better for your tranny, all the people that have had problems with it is due to the install;) and not the shift kit itself...the tranny is something only a pro should handle, and make sure whoever installs it has done it before and knws EXACTLY what he is doing:cool:

446 Posts
PB24daGrk said:
the transgo shift kit on my '01 GT was the best mod i have done for my is very reliable and actually better for your tranny, all the people that have had problems with it is due to the install;) and not the shift kit itself...the tranny is something only a pro should handle, and make sure whoever installs it has done it before and knws EXACTLY what he is doing:cool:
Depends on your definition of "better"
Read the following-written by the jerry-mod man himself:
First I’ll cover the seperator plate changes in the transgo shift kit.
Hole #1 and 1A
Hole #1 is a damping orifice for the converter clutch control valve. This hole damps the output of the converter clutch solenoid. That solenoid is only an On/Off solenoid, it controls pressure output by tuning on and off very fast. The more on time, the more pressure, the more off time the less pressure. This is called pulse width modulated, or PWM. They recommend opening this hole to .067” from it’s current size of .050”.

I do not recommend any change to this hole. As I said, this solenoid turns on and off very fast and the output goes from 0 psi to 55 psi. This hole dampens the peaks and valleys from the output of the solenoid to provide a smooth signal to the converter clutch control valve. If this hole is too big, then the valve will start to respond to the on/off pulsations, giving an unstable system.

Hole #1A is the feed to the solenoid. Currently it’s .100” in production, so there is no need to change this (this hole was recently added).

Hole #2
This is the intermediate clutch feed orifice. I go over this in my article. I recommend .081”, .100” and .125” for low, medium and high power applications. They recommend .067”, .094”, and .125”. For the most part we are pretty close. The low setting, .067”, isn’t much different than production. Starting in 1996 this orifice went to .063”, I doubt there is much noticeable difference in .004”.

Hole #3
They recommend not changing this hole. This is the direct clutch feed orifice. They recommend no change because they want you to remove the check ball. I’ll cover this later.

Hole #4
This is the OD servo feed. It should already be at .150” in production, and they recommend no change and either do I.

Hole #5
This is the forward clutch exhaust. They recommend not changing this as well. I disagree. You guys with 1994/95 cars want to open this orifice to get rid of the sag, or hesitation, at the 3-4 shift.

Hole #6

Hole BR
This is the feed for the OD servo release. They recommend at least an 1/8” or a slot OK. Most all of your cars will already be a slot. This is not a problem.

Hole A,B,C
These are recommend to be .093”. Holes A and B in any 4R70W will already be this big or bigger. The early AODE’s (1992-1993) have some smaller holes. So these do nothing for our cars. Hole C is the power off forward clutch feed. I recommend different sizes based on power, but .093” is OK.

Hole AC1,2,3
AC1 is the backpressure feed for the 2-3 accumulator. This is used on 3-2 downshifts. Most all should be .125” already, and they recommend .125”
AC2 is the 1-2 accumulator feed and it’s never been smaller than .160” so I don’t know why they even mention it.
AC3 is the bottom of the 2-3 accumulator. This is also used on 3-2 downshifts. Again, most of your cars should be at least .200”, they recommend at least .125”, and I agree.

Hole R
I think they meant this to be the reverse clutch feed, but it’s not. It’s a feed to the reverse clutch, but has never been less than .125”. They recommend .093”

EPC Relief Valve (Page 3)
They say this valve corrects (extreme line pressure due to electrical malfunction, stuck EPC valve, or crossleaks.” I would under no circumstances EVER do this. We have never seen any pressure spikes that have caused any damage. That’s not exactly true, in 1995 there were less than 50 failures from pressure spikes, but we fixed the problem. This valve would not have prevented damage in those cases.

The reason I don’t recommend this is that if that valve ever gets anything stuck in it and opens, you will fail the trans. It will cause a large line pressure leak. It doesn’t solve a problem, but creates the potential for disaster. Again, I have never seen pressure spikes that this would prevent damaged caused by them.

Valves (page 4)
Step 1 and Step 2
All these changes allow the trans not to upshift out of manual low into second and allow you to get every manual gear.

This is much better accomplished electronicly than with these mods. First off, if you pull the lever into 2 at 120 mph it will go into 2. This is a bad thing. There are values in the EEC that allow this and those should be used.

In addition to this, the pressure coming out of the solenoid pressure regulator valve is raised (Step 1) to a higher pressure. This pressure should not exceed the 55 psi from the factory. The shift solenoids, which this valve supplies fluid too, do not work the way you would think. There is always fluid flowing through the solenoids and the solenoids must exhaust the fluid that goes to them when the solenoid is off. When the solenoid is turned on, the exhaust path is stopped. If you provide too much pressure to the solenoids, they will not be able to fully exhaust, especially cold. This could cause the shift valves to start to drift one way or the other. I realize they change the 1-2/2-3 shift valve spring, but they don’t change the 3-4. Both shift solenoids supply pressure to the 3-4 shift valve. Each solenoid alone doesn’t have enough pressure to move the valve, in production. But since the pressure is raised, the 3-4 shift valve could move.

Step 3
This is the converter clutch control valve. This is a very sensitive control system and requires a very fine balance between all it’s parts. I doubt they have done the development we have to make a good control system. I wouldn’t mess with the valve at all. I do recommend the stiffer spring for 1995 and older cars. (I didn’t put this in the Thesis because springs aren’t serviced seperatly)

Step 4
The main regulator valve has the land removed that regulates the flow/priority system. If you go to my article, I don’t recommend this for the reasons mentioned in the article.

The main regulator valve spring raises line pressure across the board about 20 psi. This change is OK and doesn’t pose any problem.

More Valves (page 5)
I haven’t actually seen the new manual valve so I don’t know what it does.

The Taper spring (step 3) is a further mod to override the EEC and give you the gear you select. See above for my opinion.

Step 1
The 3-4 capacity modulator valve spring. They include a stiffer spring. This will make the 3-4 shift softer. In production starting in 1996, we actually lowered the load of this valve.

Low Valve. This is a higher spring load than production. This won’t really accomplish too much other than making the manual 2-1 firmer. It will still have the delay (or neutral feeling), but will be firmer when it comes on. This change is not a problem.

I’ll only address the new style piston. I don’t know the spring loads so I can’t really comment on much, but I’ll give it a shot.

As you add spring load to the bottom spring, the start pressure of the accumulator lowers, making a softer shift. They have you put a washer in the bottom, in my opinion the wrong way. The solid spring is similar to taking the spring out. I suspect that the solid springs limits the accumulator stroke (or travel). This is something that I do not recommend. Your better off with a light spring load or no spring.

The ball removal
This ball removal makes the direct clutch feed orifice .160”, the size of the ball hole. Like I said in the thesis, leave all the balls in. Taking this out will give you firm 2-3 shifts, maybe too firm for some (I’m getting older) but the backout or partial backout shifts will be very harsh. This harshness could result in driveline damage (U-Joints)

For firmer 2-3 shifts your better removing the spring and drilling the hole.

Overall I think the kit has some good things and some bad things. I don’t like the major reworking of the shift valve/solenoid pressure regulator stuff to give you every gear manually. I’d much rather do this in the EEC, you can still have protection from over-reving and not have the compromises. And, every once in a while, I see a car with this kit that just does not work due to all the valve replacement.

I don’t like the main regulator valve, again gets back to the priority circuit.

Most of the holes are OK but if you have a 1996 or newer trans, you won’t be changing many of them anyway.

If you’ve put one in your car, I’d like to see the production main regulator valve put back in, the ball put back in and the feed orifice opened. You don’t have to remove the manual shift stuff as long as you don’t move the lever when you are too high of a speed, sometimes that lever is tempting. I’d also like to see the EPC relief valve removed, but that requires a whole new valve body to fix.
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