novatuc

Please God let someone have an answer for this. I have a vibration in the rear of my Trans Am. It starts at about 45 mph and gets really bad around 60 mph. I have done all the searches and studied this board for hours.

I have changed the rear wheel bearings, the transmission mount and the lower control arms. I moved the wheels front to back, back to front. I have changed the rear end gears, the drive shaft and the u-joints. The axles run true with not a hint of wobble in the wheels. I have had the transmission checked. Today I put on a brand new rear yoke. I have thrown over $1000 at this thing and nothing has changed the vibration even a little.

I don't have a frickin' clue where to go next. I am so digusted with this thing I may dump it when the spring comes and I've only owned it for 3 months.

Tony89GTA

iTrader: (7)

I wonder if your pinion angle is not right, has anything been done to your suspension?

digital_burnout

have u thought about checkin out the tires. they may have a ball or may just be out of balance.

Tony89GTA

iTrader: (7)

He's moved around his tires front to back so don't think that would be it.

novatuc

Car is totally stock, except for all the new parts that is.

The car had the vibration when I bought it, but it just felt like a bad tire. Still does. But changing the wheels back to front had no effect. The vibration stayed in the rear.

little Potato

You said you changed the driveshaft but was it a stock 2.5" one from a junk yard or a larger diameter aftermarket one?

I ask because I have been fighting a speed related vibration in my GTA and had the stock shaft balanced with new u-joints and it still did it. I then got a stock one from a junk yard and the vibration did not change. From what I have found this is common with the stock 2.5" driveshaft.

And yes, I have changed and tried all of the other possible causes I can think of.

Rob

Tony89GTA

iTrader: (7)

So Rob if you had the stock shaft balanced and changed it with a JY one and it still had problems what makes you think it's still the driveshaft? Did you go aftermarket with a bigger driveshaft or something and it fixed it?

little Potato

Tony 89 GTA,

The short answer: that is the only part that has not been replaced with a new one. I will be ordering a larger one, probably later this week.

Rob

novatuc

The stock driveshaft was 2 1/2" and weighed a ton. The only replacement I could get was from a '98 V6 Camaro. It's around 2 3/4" and much lighter but still made of steel. It made zero difference.

My next two options are get the driveshaft balanced anyway, although I'm sure that will be a waste of time, and totally strip the guts out of the rearend and have it rebuilt from scratch.

Don't bother saying just pickup a rearend in a junkyard because they don't exist here. I would guess there are not 100 thirdgens in the whole province.

little Potato

Your problem sounds just like mine and the ONLY part I have not replaced with a brand new one is the driveshaft. I will be ordering a 3" or 3.5" driveshaft soon so if your not in too big of a hurry I can let you know if it makes a difference.

Rob

novatuc

Weather bureau is calling for snow tomorrow so I guess it is time to stop banging my head on the floor and give up until spring. I'll eagerly wait to see if your custom shaft worked. The thing that bothers me the most is I've had two of these cars before. An '85 Firebird that was just a great car until I cut the roof off it and welded on a t-roof which would not stop leaking and a built '85 Trans Am (with factory t-roof) which by my estimates would easily do 120 mph without a hint of vibration anywhere.

It is really scary to read all of the old posts from searches and see how many of these cars have a vibration that can't be found. There must be a way to catalog all of this crap that shakers go thru to try and get a solid car. I can't believe the car was ***** to begin with but it appears certain cars were.

Gunner823

iTrader: (2)

I had an 87 GTA with the EXACT same issue. The vibration wasn't very bad, but it was there and it drove me nuts. In fact sometimes it would seem to vanish, only to return. I did everything- wheel swap, balanced driveshaft, brand new driveshaft, took the rear end apart, etc. and nothing.

I did however notice something- and this is going to sound crazy- but the vibration frequency would match EXACTLY the wind whip noise when my windows were down. That led me to believe that somehow I was getting some type of airflow resonance over the back of the car. After dumping almost a grand into it and replacing/inspecting everything I could think of that was all I was left with. I ended up selling it to a buddy that almost never drives it on the highway and doesn't seem to mind that it shakes when he does.

I feel your pain man, and I hope you figure it out.

little Potato

The car is an 88 GTA that we have owned since 91 when it had 17,000 miles on it. It has been to 140 mph a long time ago and this vibration is something it has developed over time.

It now has 175,000 miles and stopped being a daily driver about five years ago. I am in the process of returning it to a daily driver, so I have been freshining things up a bit. The vibration wasn't really bad until over 85 mph so it wasn't that annoying, but if I'm going to go this far it is going to go away.

The thing that I have done that made a difference was change the gears. It had a 9 bolt with 3.27 and now has a 12 bolt with 3.42. The vibration now is at a lower speed, which is understandable as now the driveshaft is turning at a higher rate. This is also why I think the vibration has been in the driveshaft all along.

It will probably be about two weeks until I get the driveshaft and install it but I will let you know how it turns out.

Rob
----------
Gunner823,

When you replaced the driveshaft what size and material did you use?

Rob

85firebirdfan

hey guys, sounds like a real b***** of a problem you guys have. especially since all that work and still nil fix. could there be an out of balance on output shaft from transmission that is translating to the driveshaft from your 700R-4 (presumption). just a thought. Good luck!

little Potato

I think the output shaft would have to be bent or twisted to cause the vibration. The transmission has been rebuilt and nothing was noticed that would indicate it to be damaged. There is very little play in the tailhousing bushing and I have even changed it out again and that didn't change anything.

Rob

jayk2k3

iTrader: (2)

flywheel and axles, can do that too

rjt76

call spohn and buy a new drive shaft. also get new tires and have them balanced by an expert. I bet your vibrations will all but vanish. The stock driveshafts are not that good. mine vibrated and this cured it completely. tire balance is very critical with these cars if a weight flies off you will get this most definetly. My pickup on the other hand could care less if the tires are perfectly balanced.

little Potato

jayk2k3,

The vibration is not rpm related and the car now has a 12 bolt in it so axles and flexplate are not it.

rjt76,

Tires and wheels have been done and that made zero difference. The only thing not brand new is the driveshaft.

Rob

rjt76

get a new driveshaft. this is probably the culprit.

3.8TransAM

Forgot this in your other post.

If u have anything in contact with the subframe or headers touching, exhaust, whatever hhas been done to the car, it can cause the same thing and be almost impossible to trace.

A lot of times it leads u down the wrong track.

Make sure you check everything out.

later
Jeremy

little Potato

The car has stock manifolds and y-pipe and no exhaust parts are rubbing on anything.

I didn't find out how common it is for these driveshafts to vibrate until after my stock one was rebalanced and had tried the junkyard one.

I'll be ordering a new one very soon.

Rob

Floor guy

Try removing the driveshaft. Then remove the tail housing on the trans. Grab the output shaft on the trans and check it for up and down movement. There is a bushing in the case that can wear, and even spin. I had the exact same problem in my 87 vette, and the trans case bushing was the problem.

player 88

iTrader: (2)

also try the transmission mount and engine mounts. They do get hard over time.

The flywheel ( flex plate) can also cause this, Make sure it is tight and that the torque converter or pressure plate is tight. If these are loose a low rumble can come from the car.

My 1998 Ford F150 has a worn output bushing in the tail shaft of the transmission. I vibrates also. I though it was u joints until I crawled under there and I could wiggle the drive shaft in the transmission!

Also the pinion angle and the transmission angle are important. Not just in a vertical plane but side to side too. The factory manual has the correct dimensions.

If it is the drive shaft an old trick to correct it or the verify it is to take 1 or 2 hose clamps and put them around the drive shaft. These will become counter/balance weights. Now rotate them in 90 degree increments and see if the vibration gets better or worse. If does either then it is most likely the drive shaft. If nothing happens then it is something else for sure.

L.I.N.Y.92CAMARO

But if it was the driveshaft, wouldnt getting it balanced fix this problem?

little Potato

Floor guy,

The output shaft is not fully supported until the yoke is inserted into the transmission, so it will have movement. I agree with you that excessive movement when the yoke is in place will cause a vibration. I did replace the bushing and it didn't help.

Player 88,

The mounts are good and this is a speed related vibration not RPM. When just a yoke is in place of the driveshaft it does not vibrate.

I have not checked the pinion angle but other than from age the car is at stock height. It does not have an aftermarket torque arm or anything that would have altered the factory pinion angle in the suspension. It is possible that Strange could have welded something incorrectly but the vibration did not change after the install.

I have not tried the hose clamp trick yet but I may. It's not like it will hurt anything.

L.I.N.Y.92CAMARO,

You would think so, but this seems to be a common problem with the 82-92 steel driveshafts.

Rob

richm

Glad I read this. I have a 15th anniversary TA and at 50 MPH it starts to virbrate and get louder the faster I go. I cannot stand the noise and could never imagine driving at highway speed.

New balanced tires, new rear bearings, transmission mount, and new torq arm mounts - nothing helped - I am freaking out!

The sound is louder if not in overdrive. I have a parts car 84 TA and put this driveshaft in and the sound statred at 55MPH instead of 50 MPH.

I am about to get the driveshaft balanced and was hoping this board would help.

My catalitic converter has also been hollowed out too.

So to summarize check the tranmission seal and balance the driveshaft or buy a new one. Thanks!

little Potato

richm,

It's not the seal that can cause the vibration. There is a bushing in the end of the housing that will wear out and cause it.

I wouldn't spend any money or time on a stock steel driveshaft. Get a new one that is a larger diameter than stock.

I replaced mine with a 3.5" aluminum one from Precision Shaft Technologies and it seems to have fixed the problem. I have not been able to try it at speeds over about 75 yet but the noise and vibrations seem to be gone now.

Rob

richm

Well, I took my drive shaft out and had it balanced. No luck. So I purchased a new alum 3.5 drive shaft. It made a huge difference but it is still there. The bushing seemed fine may be I don't know what I am looking for. Another thread said I should check the crush bushing in the rear end. I can't believe how difficult this issue is. Transmission, shocks, rear end? What should I try next. Thanks!

little Potato

With the driveshaft installed the slip yoke in the transmission should have almost zero movement up/down or side to side. I haven't seen anything that says what an excessive amount would be.

The crush sleeve in the rear end sets the bearing preload on the pinion bearings. If you can move the pinion front to rear it is bad.

What type of mounts did you use for the torque arm and transmission? I took out the urethane transmission mount and replaced it with a new rubber one and it made a noticeable difference.

Rob

novatuc

Hey Potato
Did putting a regular trans mount back in make a big difference? I replaced my worn out stock one with a poly mount. Someone else had mentioned the poly material will amplify vibrations and stock rubber will absorb vibrations to some degree. I'm laid up for the winter now so I haven't worked on it for a while but I do have an aluminum driveshaft on the way.

Gallileo60

I know you said you moved the tires around, BUT I just went thru this thing with mine, and I had a slightly bent rim...It was so small a bend you could not see it...My wheels were new Voxx's... I am fighting with Discount now as I claim it was a factory defect...I had moved my tires, and had 6 different balances done on the car...We replaced the wheel, and the problem went away....It took me from october till last week to figure it out..I had replaced the rotors, wheel bearings, and so on...Just thought I would add this for you...Good luck, Tom

joecautela

iTrader: (1)

Has this car been sitting a really long time? Like maybe the tires have squared off or the belts in the tires have shifted. Happened to me a while back when I had a car laid up over a year. The tires we're like off the flinstones car. And they were new. Once replaced the vibration went away, Joe

richm

I'll have to grab that thing and see what play there is. I did replace the transmission mount with a new one from carquest. It seemed a little taller than the one I removed (which I kept). I'll put it back in and see what happens. maybe I was sold the wrong one?!

I put a new torque arm isolators from GM - both sides.

I put new Goodyear HR radials on in August. I'll double check the wheels. 15th anniversary rims were often out of round from what I've read. I'll re-check those too. Thanks for the ideas - back to the garage!

LoneStar666

wow i have the same problem in my 1992 Z28, up around 55+mph there is a noticeable vibration, and gets worse with engine RPMS which leads me to believe that it actually is a defect with the driveshafts that came stock on our fbodys

(new bfgoodrich g-force sports, zero'ed out on the balancer... but vibration is still there, though not as bad when the tires were unbalanced)

little Potato

Novatuc,

Yes, using the stock rubber mount did make a noticeable difference.

Rob

joecautela

iTrader: (1)

Novatuc, I was thinking last night about your thread last nite after I put the sfc's on my car. You said you changed the torque arm bushings and I think also the trailing arm bushings? Anyway..did you tighten everything back up with the suspension loaded? Reason being that if you frame jack the car to remove everything you've "unloaded" the suspension when you go to retighten everything. The car has to be supported by the suspension when you tighten everything back to simulate actual ride height. If the rear axle is just hanging and you tighten back the torque arm, trailing arms and such you'll get a hell of a vibe like you're describing, Joe

novatuc

Good thought Joe, but I always use jackstands under the axle to tighten things up. I have this dream that I'm gonna put the aluminum driveshaft on and it'll all be cured. Of course I had the same dream before the wheel bearings, and the LCA's, and the u-joints and the rear yoke, etc, etc. I guess I just have a dream.

CBR1000RR

iTrader: (1)

I have a 91 Z28 with a five speed manuel transmission and I've been fighting the same problem. I replaced the drive line with a new 3" aluminum drive line from inland empire drive line. Still have the same vibration. The vibration gets
really bad around 100 mph when I let off the throttle. Then when I get back on the vibration some what gos away, but is still noticeable. Its not an engine vibration because if I take the trans out of gear and let the engine idle I still have the same vibration. Feels like a drive line vibration. Replaced everything in the rear end, didn't change. ??

joecautela

iTrader: (1)

I've been following the discussion about the driveshafts and all related bushings and hardware and am wondering if in some of the cases the problem is somewhere else. What I mean is this, are all the vibrations felt in the seat? Seat vibrations and rear window vibes usually indicate a rear end vibe while a steering wheel vibe will indicate a frontend problem. But there's always that oddball combo. Years ago I had a chunk come out of a harmonic balancer after incorrectly jacking the motor and I didn't know it. Man that put up a hell of a vibration all the way from front to back. Another time there was a dry, slightly overtight front wheel bearing. Another time was a slightly seized rear caliper. My racing Alfa Romeo developed a bad rear vibe which didn't go away till I changed both rear axle bearings. So all I'm saying is that after having a driveshaft professionally balanced and new u-joints installed there's still a lot to check. Oh btw, I chucked all those urethane bushings out of both the camaro and the alfa and went back to stock rubber. The harshness and vibes from those on V rated tires was insane. And my alfa is not a spider, It's a 2200lb 160hp live rear axle honest 132mph car. Dual carbed, DOHC Hemi straight four, all aluminum mtr 5spd and aluminum full posi 3:60 rear. Hell, no one even talked about a 4wheel computer alignment, plus a 4 way cross measurement to insure tracking. So yeah, I think there's a bunch more to check IMO, Joe

novatuc

Hey CBR1000RR, you are not filling me with confidence here. I was hoping the aluminum shaft I bought might be the cure all since the replacement steel shaft I got didn't change a thing.

Joecautela, I agree with everything you said. I've worked on aero jet engines for 15 years, so you would think I'd be able to work on a 23 year old clunker but so far it's getting the best of me. I'm going to settle back and apply the principals we use in the aero industry to track and fix problems. I haven't been smart enough to do that with the car, go figure. Instead I just dove in and started changing parts which so far has done nothing. There has got to be a happy end to this, but damn the frustration level is high. I will begin the battle for the 2007 season starting next week. With the grace of God, plenty of beer and much profanity, I will triumph.

talover111

sounds like an axle to me

joecautela

iTrader: (1)

novatuc, good luck man, get LOTs of beer! One time a while back I was hunting a buzzing under the dash of the Alfa. It was always right around 55-6500r's. So there I am laying under the car just looking around and I dozed off (too much beer!). I woke up and just kinda focused up on the trans mount. I had prolly looked at it a hundred times already and taken it apart that many too. Anyways 2 of the lockwashers had cracked and started squirming out from under the bolt heads creating just enough slack for the bolts to start backing out. Well DAMN! you know the rest. Sometimes it's just there staring you in the face, other times you just gotta hunt it down and kill it! Keep us posted? Joe

RBob

iTrader: (1)

Another possibility is the pinion yoke on the rear. I've seen this several times where there is a hair of runout, which causes misalignment of the driveshaft to the pinion shaft. To check this need to use a dial indicator on the inside of the flanges (where the U-joint indexes).

RBob.

novatuc

I changed the pinion yoke and it did absolutely nothing, except cost me $160. At work, I have access (as long as management doesn't find out) to equipment that would blow most people away. After changing the yoke I took the old one in to measure it. It was damn near perfect. Probably gonna have a lot of drive train parts for sale by the time I find this problem.

Gallileo60

I do have less vibration with the new aluminum drive shaft, and new u joints, but I STILL Have some vibration.Really bums me out, above 70 it is apparent.Like you, I have replaced most everything....

turbotdc3

shes probly been wrecked and had a half-assed fixing job.

novatuc

Na, that ain't it. Too many cars here have or have had the same problem, including some posters who mentioned their cars developing the problem after years of ownership. My guess is this is a problem that a lot of other model vehicles have but for some reason the third gen is very sensitive to.

musclecarfan87

I have the same problem y'all are describing, with my 86 'bird....I haven't tried anything yet, but will start trouble shooting soon...I was thinking it was due to possibly my wheels being un-balanced....but after reading this thread I might oughta think about other possible culprits to my problem....

On the other hand, I do keep having problems with my tranny mount. I have the 5speed manual, and it keeps coming loose from its mount.....keep having to tighten it back up.

novatuc

Don't take this wrong 86redtop but I'm kinda glad you have a vibration problem too. I think every other car here I read about was an automatic like mine. I was thinking maybe something in the auto was causing a problem that I will never be able to find on my own. Thanks to you I can hopefully rule out the 700R4 being the source of the vibration.

joecautela

iTrader: (1)

I think the 700R4 is a pretty stout and well made unit. I've had a couple go over 130K miles with no problems. I did notice withe the Iroc that tire pressure was critical. I have Cooper's-245-50's and anything over 30lbs of air sets off a vibe, but it's all due to road surfaces. Even driving 20 miles or so till the tires and struts are really warmed up doesn't help. I now keep them at 30lbs front and 28lbs rear and no vibes at any speed cold or hot. Just n idea for guys with the minor vibes. The big shakin vibes must be something else, Joe