yeah both driver and passenger side are the same....but the last post is correct there were 2 different splines...i dont know what the cut off was but if you search you will find it

Ok, great post but whats the rest of the story? I have the exact same issue with my 87 T-5

Sorry - I never posted the result!

I'm now running a Moser 9" rear, and vib problems that I had have gone away.

I still have the 10 bolt sitting on the floor of the garage, but I have not pulled the axles on it. No need to now!

EDIT: NO IT DIDN'T GO AWAY!! I guess it wasn't really gone, but did seem to improve a lot right after I changed out the rear, but it's now as bad as ever. Starting a new post since this one is too long to add on to...

Have you checked out this thread?
http://www.thirdgen.org/techboard/tr...vibration.html (drivetrain vibration)

What were the symptoms on your car? (I.E. when did it vibrate?)

I copied this from my 'vibration thread'. Whether it's of any use to you, I can't say. I will tell that this drove me nuts for a couple of years. The car would vibrate in park or neutral starting around 2500+/-. The same thing at highway speeds in any gear. You could modulate the frequency and intensity of the vibration by rolling in and out of the throttle but it always was around the same rpm. At higher engine speeds, there's too much other noise and shaking to tell if it's significantly worse or not.

"For the record, EVERYTHING in the drivetrain has been removed, replaced or rebuilt at least once. Check out the 'vibration' thread in the Tech/General Engine forum for the list.
I've been driving with this problem for a few seasons and had resigned to myself to accepting that this is how the car is going to be.
Recently I had a 700R4 3-4 clutch go away. This trans with the TCI Street Fighter convertor helped the car to it's first sub 13 second pass.
I found a low mileage 700R4 from a forum member, did a quick shift kit, basic mod procedure and installed it with same convertor. Now it only took 4 quarter mile passes to cook this transmission ( that's another story ) however, the vibration is GONE. I have only 1st and 2nd gears to test with but I can say at all previous test rpm's, there is no longer the ' harmonic vibration' that was painfully obvious before.
I can come to two different conclusions. Two previous 700's ( I'm on my third ) and 3 different convertors all combined to produce the vibration. This I find unlikely.
Or the relationship between the flexplate and the convertor had a stacked up tolerance with respect to balance ( and I have been using a new SFI flexplate and new TCI convertors as well as an engine balance). After the latest installation, the convertor and flexplate were bolted together not using the previous index marks. Now it's smooth as silk.
After investigating further and going through the GM manual, I've come across a chapter titled " Flywheel Assembly/Torque Convertor Clutch Vibration Test Procedure ".
Who knew?
The test describes checking for vibration in park or neutral, decoupling the torque convertor, rotating it 120 degrees and hooking it up again. Check for the vibration and repeat the procedure if the vibration is the same or worse. Looks like when I reinstalled this latest trans and convertor I inadvertantly came across the best connection.
It was a long time coming. And expensive too although I must say I've collected and installed a lot a top quality parts along the way."

As the test says, this applies to auto and stick cars. Keep in mind that I had swapped out multiple transmissions several times and always had the vibration until the last time. Now it's indexed and I'll put it together them same way next time.

Thanks for the help skinny z, but I don't have the same problem really.

In neutral and revving, no vibs at all. In gear and only around 60 plus MPH the gearshift vibrates and buzzes, and seems to get worse when the driveline is light loaded or unloaded (like slowing down for a stop light) - especially when I push the clutch pedal in while slowing down from 60 MPH until around 40 MPH, then the vibs stop.... If I goose it and load up the driveline it still vibrates, but not as much as when light loaded or decellerating from 60 or so MPH. Accelerating up to 60 MPH or so, it's smooth. The flywheel only bolts on one way on a stick car. It was resurfaced and balanced again before this buildup and weight was taken out. As a matter of fact, they said it was off a bit but it didn't make a difference.

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 gage, with tires on or off, drums on or off - but I can't tell what's vibrating.

There's only two things I have not checked:
1. Pinion angle (but if it were off, wouldn't it vibrate at all speeds?)
2. Bellhousing offset (but I still run a stock bellhousing so can it be off that much, and again wouldn't it vibrate all the time??)

Can ANYONE think of what else I could possibly do to correct this?!?!? I'm open to all ideas here.

I've decided to keep this post going to it's conclusion, even if it means the demise of my Thirdgen because there's great info in here given by so many on this subject.

Well confuzed1, if you're still out there, don't feel alone! My 89 IROC is giong throught the same senario. My vib is at 75. Rebuilt rear end, new tranny, new u-joints, driveshaft balanced- still there. Drive line related- still present with clutch in or in neutral with engine off. I've been talking to a lot of people I trust and this is one of the hardest puzzles to solve.

Right now I'm looking into an aluminum drive shaft. I converted to a TKO 600 and the yoke could be about an inch further into the tranny so I may get a longer shaft made. EVERYTHING else has been changed or checked. It's sooo annoying that I can't run my car at the strip like this. Damn!

antman89iroc - Yeah, I'm still around...and the problem is not solved yet. I've been on this board quite a while, and this vib problem in thirdgens isn't uncommon unfortunately. I've read many posts with the same basic vib symptoms, and with almost all of them, a root cause was never found. More than a few gave up on thirdgens altogether due to this issue.

Funny you should mention an aluminum driveshaft - I JUST got one myself from a 98-02 Trans-Am. I intend to double check the driveline pinion angle prior to installing it, and see if it helps....it's really the last thing I can try.

Just to let anyone know that reads all this. I finally tried an aluminum driveshaft, and it worked like a charm!!

It was mentioned 10 posts into this whole thread, but I kept listening to my machine shop that said my stock steel shaft was balanced. There's something inherently that goes wrong with the stock steel shafts, because after I put in this aluminum one, it's like a whole different car!!

100 bucks on Ebay well spent!!

Yeah I was looking for an aluminum DS from a 4 gen but it won't work for my car since I switched to the TKO 600 tranny and it uses a different yoke. Actually the 4 gen shaft is 1/2 inch shorter (at the tube) ant the stock one is really 1/2 inch too short, so if I were to switch yokes it would be 1 inch short. Bummer!

I am having my steel shaft re-tubed 1 inch longer to better engage the tranny and, of course, be straighter and better balance (I hope!). I don't have a lot of confidence in the balancing at my local shop since they only spin it to 2000 RPM to balance. That's about 40 MPH with my gearing. But we'll see...

Just backing you up on this one again.....same problems with mine...fixed with driveshaft....there was a article in car craft about how the stock steel driveline worbbles or bends at speed...the fix...aluminum driveshaft!! works great!!

Is the vibe gone or just better? I've been fighting this for a while as well. My aluminum shaft definitely made a big difference to how the car feels but the vibe is still there all be it at a higher rpm.

I'm in the process of changing the entire drive train (engine, trans, flywheel, clutch, drive shaft) save for the rear axle. So we'll see where I end up.

Jon

JSD 04/10/09

i had a driveline vibe at 65-70mph that was just ridiculous, threw the stock driveshaft out in favor for an aluminum ls1 shaft, same vibration, threw that out for a balanced 3" spohn driveshaft, same vibration, finally threw in a denny's nitrous ready driveshaft and bam smooth as butta

After driving the car a third time after replacing the driveshaft.....vib is GONE - at least up to 80 mph....cops were everywhere, and I couldn't push it past there.

The vib problem I had didn't seem to have anything to do with engine rpm. It had everything to do with whatever speed the driveshaft turned at 65-70 mph. I could push my clutch pedal in at that speed, and I could feel in through the pedal, I could shift it in neutral at that speed and shut the engine down - it was there until speed dropped below 60...could also feel the vib in the shifter and hear it buzz.

Never felt it in the steering wheel.

Glad to hear you sovled the problem. I had a vibration problem with my Ford Ranger a couple years ago. The guy that works on my vehicles went nuts trying to find out what it was. Finally we took it for a test drive one day and after getting out of the truck at his shop.........I could smell something was really hot.
Here it was the emergency brake was sticking. It was making the drum so hot it was warping and causing the vibration. Once it cooled it was fine, but once I got up to highway speeds, it would shake like hell.
Disconnected the emergency brake and have had no problems since.

My suggestion to everyone, always check your brakes if you get a vibration problem.

Re-tubed DS and made it 1 inch longer. 99% of vibration is gone. Going to replace trans rear bushing and see if that helps. But at least it's driveable!