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Discussion Starter #1
I have a 90 gt with:

GW LCA's
FRPP UCA's
FRPP 5 lug drum and axle kit
a freshly rebuilt 8.8 with 3000 miles on it (new bearings and all)
Tokico blue shocks
C springs
ES coil spring isolators

On the way into work this morning the car was running fine, then all of the sudden I developed a thumping noise (feeling) in the driver's side rear. I noticed that under acceleration, the noise goes away for the most part. In neutral just rolling, the noise is the worst. Going around a right bend the noise gets louder, and around a left turn the noise just about goes away. It really sounds like with each revolution of the tire the there is a thump. The noise (feeling) is so bad that I don't think I'll make it home from work today unless it is on a flat bed truck. I can't figure what the problem could be, because everything is pretty much brand spanking new (and drove fine for the first 3000 miles, no noises or vibrations at all.) The brake hardware is not new.

I looked under the car: sway bar tight, LCA bolts at the axle end appear torqued the same as they were when I installed the stuff, shocks tight at the axle and in the hatch area, springs seated just fine. Everything external looks fine. Lug nuts are tight. Doesn't seem to be any play in the wheel side to side or in and out (even though I can't tell all that well seeing as how the car is on the ground.)

Seems to me that it can't be the driveshaft/differential because in neutral the noise is at it's worst. The driveshaft doesn't turn in neutral, correct? Neither do the pinion and ring gear, correct?

Right now the car is sitting at a ****hole garage, where they said they'll "try to squeeze in looking at it today, but there are five cars ahead of you." I can't imagine what kind of shop gets five cars fixed a day and makes money...unless they are raping each with a broomstick. So I'm a little bit uneasy about how I'm going to get the car home/getting raped. I usually do all of my own work, but I'm kind of stuck right now as this is my only car.

Any ideas as to what could be wrong? My only thoughts are that something broke off inside the brake drum, but that doesn't explain why the car isn't thumping nearly as bad when accelerting.

Please help if you can!
 

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Its really hard to troubleshoot without the car, I know that you can't count out driveshaft or rearend. Neutral only disengages the tranny to the motor. Your rear wheels are still turning the ring and pinion and driveshaft. Driveshaft noise really wouldn't go away at times and rearends can do a lot of strange stuff, but it isn't too likely. That part about it going away on turns and stuff is baffling, I really don't know what to say other than to have someone look at it. In the garage they can screw you with a diagnosis fee, but other than that tell them no. If you don't feel something needs to be repaired, get a second opinion, you can only get screwed over if you let them. Post back with what they say is wrong.
 

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Sounds like the drive shaft u-join has locked up. This is quite common when a u-joint fails. I had one go out on me and the symptoms were the same as your experiencing.

And yes, your drive shaft and ring/pinion are contstantly turning if the car is rolling whether you are in neutral or not.

All that will need to be done is drop the drive shaft, and replace the offending u-joint. While at it, replace them both and get sealed u-joints (don't get the crappy ones with the grease fitting!)

Tony
 

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I'd suspect an axle bearing
 

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Here is the only help I can offer. When the car is rolling and the transmission is in neutral the ring and pinion, and the driveshaft spin because the wheels are moving. Ever turned the rear wheels while the car is in the air? Solid mechanical connection between components. I think the transmission spins too but being in neutral there is no power transfer. I assume that you don't hear the noise when stopped. I don't know what it could be. From what you say it sounds like suspension, not drivetrain. Usually the driveshaft problems appear at certain speeds (i.e. the vibration gets worse the faster you go). Just wanted to help clear up one of your questions. Good Luck.

Stanman ;)
 

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yeah, but when they outright fail they'll grumble and thump
 

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Litemup68,
No flames intended. The only system that directly disengages the tranny from the motor is the clutch (on a manual at least). I didn't check to see if we were diagnosing a auto or stick car. When the clutch is engaged and the transmission is in neutral, the trans input shaft spins at engine rpm but no power is transmitted. Not sure about auto trans though. Don't have one so I never paid attention. Once again, no flames just FYI.

Stanman
 

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Discussion Starter #9
LXH89 said:


That usually makes a WAH-WAH-WAH sound at speed. At least mine did!

I love describing sounds...

Tony
Oh god, I had a "Wah-Wah-Wah" sound at speed ever since I installed the rebuilt rearend with the GW LCA's. I thought that the GW LCA's were just transmitting a little noise, maybe a little bit of gear whine (it wasn't that bad.)

I also had a bit of a clunk after a shift when I got back to the gas(figured it was either some slop in the transmission or the driveshaft, but it was so negligible I figured it would be fine, at least for a while.)

I'm at the mercy of the auto repair shop right now. I've never had someone call me after they diagnosed a problem before, they just usually go ahead and fix it and then give me the price when I pick it up. I guess I should call them at lunch time and tell them to call me after they find the problem and before they start throwing parts into it.
 

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Discussion Starter #10
StanMan said:
Litemup68,
No flames intended. The only system that directly disengages the tranny from the motor is the clutch (on a manual at least). I didn't check to see if we were diagnosing a auto or stick car. When the clutch is engaged and the transmission is in neutral, the trans input shaft spins at engine rpm but no power is transmitted. Not sure about auto trans though. Don't have one so I never paid attention. Once again, no flames just FYI.

Stanman
So you are saying that with the clutch in, the driveshaft does not turn? This is a 5spd car. I'm confused on this.
 

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5.0CPA said:


So you are saying that with the clutch in, the driveshaft does not turn? This is a 5spd car. I'm confused on this.
With the clutch in, the driveshaft will still turn. The clutch is only disengaging the engine from the transmission.

Tony
 

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When the wheels are turning the driveshaft turns also. Vice Versa.
 

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Discussion Starter #13
This really feels like it is on the driver's side rear, not the middle of the car where I'd think you'd feel a bad driveshaft U-joint. We'll see, though. I'm going to stop down at lunch time and tell them to call me once they get a diagnosis.

Thanks for all of your help guys,
Dan
 

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What I was saying was related to the 5 speed car, I assumed that for some reason. When riding with the clutch in, the motor is disengaged totally from the tranny. If moving with clutch in, tires are still spinning ring and pinion and driveshaft is moving. When the car is in neutral and moving with the clutch out, the clutch is engaged, but to no gear so it is comparable to having the clutch in. No power is being transferred, thats all. Driveshaft and rearend are still spinning. No matter what, if you are moving, the driveshaft and ring and pinion are still spinning. Thats what I am gettin at.
 

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Litemup68,
I understand where you are coming from. Sorry to antogonize you. We cool?
 

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Discussion Starter #16
Well, I got the car back at the end of the workday. Unbelievable, but the lug nuts on the driver's side rear were loose, causing the knocking sound. I can't understand it, because like I said I didn't see any play in the wheel, although the car was sitting on the ground.

This happened, according to the mechanic, because I installed aluminum wheels and never re-torqued the lug nuts. That I don't understand either, because since putting these wheels on (about a month ago) I've had them off about five times, retorquing them with a torque wrench everytime to 85 ft./lbs. I must say, this is probably the most embarrassing thing that I can remember involving cars. The mechanic even snickered on the other end of the phone.

Thanks for all of the replies, and I'm sorry to have wasted your time.
 

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hey 5.0CPA:

That has happened to me before. Had to stop on the side of the road, take out the lug wrench and retighten the lug nuts. Felt like an idiot.

By the way.... is your car still leaning? Did you ever find the problem or a fix?

Mine still leans, but im about to install some koni struts and shocks, MM subframe connectors and im going to add an extra set of energy. sus. isolators up front to see if I can regain alittle ride height. How are those coil overs riding? I was thinking about getting a set, but I really dont think I need them right now.
 

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I wander if some one tried to steal your wheels??
Makes it less embarasing...Atleast you replied back!!
 

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Discussion Starter #19
xr8240 said:
I wander if some one tried to steal your wheels??
Makes it less embarasing...Atleast you replied back!!
Never thought of that. That would have made me feel like less of a fool.

I hate when people start a thread, get a bunch of suggestions, and then never reply back to explain how things turned out because when someone uses the search function because they have a similar problem, they only get half the story. But trust me, it was hard typing in "the lugnuts were loose" after guys like MFE take the time to try to help me:)


Black89GT,

Nope, haven't gotten rid of the leaning yet. I absolutely hate these D&D coilovers. The sleeve is rattling against the strut body real bad, and it is very noticeable. I'm sure others have had good experiences, but I have not.

I take it you've been to my website? I have a whole page dedicated to the "leaning mustang club." My next step are adjustable ride height LCA's, as I think about 7/8" difference in the rear would allow me to run my front coilovers at exactly the same height. I'm still afraid that even with the adjustability in the rear that this isn't going to be straightened out, but there is only one way to find out. It's taken me a few weeks to get to the LCA's because I've had a health problem, but I'll get back on it in a few weeks. I didn't forget about you, and I'll PM you with pictures and results after the LCA's go on.
 

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I like axle bearings. When did you have these replaced? If you havn't, then I give 9 to 4 your axle bearing has gone. Ford C-clips and axle bearings, need I say more
 
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