Hey all,

I'm seriously considering getting an aluminum driveshaft out of a 98-02 Trans Am to see if that will end a vibration problem I've had since I've owned this car. I did all kinds of searches, but I've found nothing definitive that says aluminum driveshafts solve vibration issues. I have a very long post of many things I've tried (4 pages worth) and nothing has completely solved it. Here's a short list:

The following has been tried/done:
- All tires balanced twice, and rotated front/rear
- Flywheel balanced twice
- Driveshaft balanced three times
- 2 different transmissions
- 2 different engines!!
- 2 different torque arms
- 2 different rear ends
- 2 different clutches
- Slip yoke bushing replaced
- UV joints replaced
- shifted driveshaft U joint mounting 180 degrees each end at a time.
- New engine mounts
- New transmission mounts
EDIT: Also forgot to mention that Ive tried 2 different styles of transmission crossmembers - one with secondary mounts, and another without.

-Car has never been in a major wreck, frame solid. I've had it on a rack, with the rear suspended and it will vibrate the entire drivetrain at 60 plus MPH on the speedo, with tires on or off, drums on or off - but neither me nor the mechanic could tell what was vibrating, we just know something is.

-Just got done checking pinion angle too, and it's set at -2 degrees which is within spec from all I've read.

The ONLY original part left in the drivetrain is the driveshaft, even though it's been balanced 3 times. I'm thinking maybe the shops might not spin them fast enough when they balance them?? So really I'm at a loss here...unless you can think of ANYTHING else to try...

So the big question......DO YOU THINK AN ALUMINUM DRIVESHAFT WILL SOLVE THIS??

 

I have a little over a full year of experience running a driveshaft shop. Not bragging, just background info. I'm suspecting the yokes are slightly out of phase. There are 2 main types of balancers, and neither one is good at catching this every time. One type can spin faster than the other, but faster can also be less accurate in a way. fast will exaggerate any imbalance, but you hafta slow it back down to read where exactly. So, if your yokes are out of phase, then switching to any driveshaft that is in phase will help, whether steel or aluminum.

 

For ~$100 it wouldn't hurt to try. I'm in the same boat as you, replaced everything from the engine back and still have a small vibration 70+mph. The aluminum driveshaft did help to lessen the vibration though.

 

GM/Dealerships often swapped out steel for alum in thirdgens when the vibration issue raised its ugly little head. Whether it'll help or not....

JamesC

 

Thanks JamesC - I read a couple of posts that stated that GM switched to aluminum shafts for vib issues while I was searching.

calebzman - Like you, I've found this to be VERY frustrating....I mean to the point where I'm willing to get another thirdgen and transfer all my go-fast parts if I have to. I hope it doesn't come down to that though. My car starts to vibrate around 65 mph through 75 mph....right at highway speeds....

I didn't own the car since new...so I don't think it did it when it was new. I saved it from the crusher most likely. It had sat in my in-laws driveway outside for around 7 years on 4 flat tires and it didn't move at all - then I bought it.
I always wondered if the driveshaft just hanging there and not moving at all for that length of time could have "bowed" it some weird way....but you'd think if the DS was that bad, no one could balance it??

Thx for the replies, I went ahead and bought it - should be getting it shipped within 7 days. I really hope this works. I'll post up if it does.

 

I had the dealership swap out my driveshaft on my 4th gen because of vibration, but they took out the completely unbalanced steel one and replaced it with a balanced steel one. It transformed the car.

If you driveshaft is balanced, it is balanced no matter what speed you run it up to (within reason). However, you can balance a driveshaft with bent yokes and/or cracks/bends in the shaft itself, and you will get mad vibration when you run it up.

TA

 

hmm so if i take my 84 Camaro in, they'll change it? ^.^

 

I've had a similar issue at the same speeds. I switched to an aluminum DS last summer and it helped alot. The vibration is still there but at a higher speed so at least I can travel on the highway without my teeth chattering. For the $90.00 + shipping off Ebay it was well worth it.

Jon

 

If the driveshaft is the problem then an aluminum one will fix the vibration. As long as the aluminum one is OK. If used there may be an issue with it (you don't know if it has been abused).

On my '92, when new it did not vibrate. Over time it started to, and got so bad that driving at 65 MPH was not recommended.

I replaced the driveshaft with a low mileage OEM steel shaft. Vibration decreased significantly. Again, over time the vibration came back.

So I bolted in a brand new LS1 shaft (2002 MY?). This is the one with the damper on the front yoke. The car has never been smoother at highway speeds. Even better then when it was new.

My feeling is that there is something inherently wrong with the way these cars are set up. Part of the reason I think this is the lengths GM went with different rear transmission mount and cross member systems.

Double layered and cushioned cross members. Liquid filled transmission mounts, spacer plates. Soft rubber in transmission mounts.

And the driveshaft issues. What makes the set up so sensitive to vibration that after a period of time the driveshaft starts to vibrate. The slightest bit of wear in the U-joints? And even after replacing them and having the shaft re-balanced they still vibrate?

Something just doesn't seem right.

With the aluminum shaft I can enjoy cruising at highway speeds. Should have installed it many years earlier.

RBob.

 

I once sold 60+ used JG1 alum shafts, the so-called 1LE. I always recommended new U-joints, but aside from that, a quick visual will tell the tale: A dent or bend is obvious, so is the loss of a balance weight (look around the front and rear of the shaft. If one's missing, you'll clearly see where it once was).

JamesC

 

I have a vibration I can't shake (pardon the pun...) on my car as well!
Same symptoms, same attack at fixing it.

Except in my world (with blue skies and all that) an aluminum driveshaft is $400. Balancing a driveshaft is $120. So i've balanced my stock one twice and it still shakes. I'm more inclined to think it's some parts in the rear end - but I really want to hear how yours works out.

Unfortunately my T10 setup means I have an oddball length DS, not interchangeable with the T56 length in the 4th gens

 

I had my steel DS balanced (Yep, $120.00) and it made no difference. But after swapping in the aluminum one..big difference. I haven't actually solved the root cause of the vibration only minimised it's effects. Better than nothing though!
Jon

 

A local friend of mine told me he changed to an aluminum driveshaft, and his car drives like a dream now.

I read somewhere that there is a certain "do not exceed" MPH rating with each driveshaft, steel, aluminum, and carbon fiber. Something to do with the frequency of the vibration possibly causing cataustrophic failure. Is there any truth to this?

 

Hey, thanks for the replies everyone!!

I bought a 98-02 driveshaft out of a Trans-Am, but I had to take it to the machine shop to get the plastic injected stock rear u-joint removed, and my conversion u-joint with internal clips put on.
RBob - That's the one I got. It's in perfect shape. I didn't need to replace the u-joint on the yoke side of the shaft since it was like-new. I agree with everything else you said too...I think the drivelines on these cars were problematic from the start. I've tried both styles of tranny mounts on mine. It's encouraging to hear the aluminum LS driveshaft solved your vib issue - I know I'm crossing my fingers!!
So you have the dreaded vibs too Sonix?!?!? I had my driveshaft balanced THREE times....didn't do squat for it. Hate to tell you, but i doubt the rear end in your car has any issues....but you never know...
Well - yeah I believe it....Everything has some sort of resident frequency, and EVERYTHING will vibrate no matter how well balanced. There's alot of variables that determine at what frequency something will vibrate at, such as mass, material, density etc.... (In this case "frequency" being speed or RPM's.... The key is to balance within a range it will be used in so it won't vibrate at that speed....there's really a lot to learn when it comes to vibration analysis.

Anyways, I'll let you guys know if this works or not!!

 

OK - I got the aluminum driveshaft installed, and it seems to fit great. Then I decided to go ahead and check my driveline angle a different way. I know I said I checked it before - and I did (In post #1 in this thread) - but I only measured the difference between driveshaft angle and rear pinion (as per the BMR website)....but....

After doing more searching, there's another way to measure everything. Basically while the drivshaft is out, you place an angle gage across the rear trans seal to determine output angle (Mine was -3 degrees), then you measure across the rear end yoke (I got -1 degrees)......both the rear of the trans and the yoke on the rear are pointed slightly downward.

So how does the math go for the final measurement?? Do I add both negative numbers together?? (-3 + -1=-4) -or- should I subtract the numbers?? (-3 - -1=-2) ????

 

And yes, I had the rear of the car on ramps, and the front had jackstands under the front lower control arms - car was sitting level when I took the measurements above...

 

Well, after more searching it seems the pinion angle is -4 degrees. Not sure whether that's too far out or not. So long as it doesn't rain (or snow) tomorrow, I'll get it off the ramps and stands to give it a test run with the different driveshaft! I hope it at least helped...

 

Here, check this video out. Steps you through the setup process and tells you what angle to start with.

http://www.youtube.com/watch?v=UAQgLbhQ0uk

 

I read an article in car craft, I believe, that said that the factory steel likes "worrble" or "bend" at higher speeds, their to small around or something, but...I have had two different shafts, both balanced, both steel...no luck, had bad vibration at same speeds, near 70 or so on up.....I got a aluminum line, and guess what, vibrations went bye bye...I'm convinced.

 

WOW!!! - I just took my first drive in it since putting the aluminum driveshaft in it...I can only say....WOW

Seriously - it's a different car now! No more buzzing through the shifter, no more vibrating clutch pedal, no more vibs during hard acceleration...world of difference all around! The entire drive in it was smoother....dare I say ALMOST "refined" for a beast!!

I should have done this 3 years ago, but I listened to my local machine shop that balanced my steel driveshaft - they kept saying "it's not the driveshaft, it's balanced. It must be your pinion angle"

Well, the pinion angle might not be dead-on, but that obviously wasn't causing this vibration I've had all this time. It really WAS that stupid stock steel driveshaft this whole time!!

I'll update my other long post from a few years back too, (Vibration problem has me stumped) -just so everyone knows all I went through before discovering this!! I think I can trust it enough to put it on the dyno now, and see what kind of power I'm putting out.

 

It's amazing when I tell people that and they get the same result I did.........If you have a vibration around 65-70 and can't get rid of it.......it's the steel driveline...throw it in the trash.... get an aluminum...I'm happy that fixed it for you...

 

Son of a....
Alright alright, i'm going to see if I can steal an aluminum shaft from a crown vic cop car, and just get it shortened and put conversion u-joints in it or something. Probably a lot cheaper than a new custom made shaft ($400 or so..)
My T-10 setup means I need one the length to fit a TH350, so the T5, T56, Th700R4 is too short..

Thanks for the heads up confused! I'm saving my pennies now!

 

Good to hear that it fixed the issue. On these cars the aluminum shafts definitely make a difference.

As for the balancing of the steel shaft, others have said the same. It just doesn't seem to help.

Recently on another car (not a 3rd gen) was a steel driveshaft that I had built from a longer shaft. Grabbed a decent shaft from a station wagon, had it shortened, new U-joints and balanced. It always had a slight vibration to it. Very noticeable at the track (higher speeds).

Put a Denny's HD steel shaft in. Smooth as glass. Night & day. One major difference is that the Denny's shaft is larger in diameter.

I've been thinking that the smaller diameter shafts tend to bow at highway speeds. Which is what causes the vibration. Not necessarily the critical speed type of harmonics. But just that the driveshaft isn't stiff enough to run true.

RBob.