[Grant Miller]

One thing I did was to run the car on jackstands with the axles and brake drums removed. That way you can eliminate the axles and brake drums (and wheels/tires) as the culprit. Just make sure that you don't hit the brakes!!

[Grant Miller]

Originally Posted by getmygoat

Also - when you ran without a driveshaft, did you end up with oil everywhere? I've considered that but assumed without a yoke the trans would leak like crazy.

I also ran my car without the driveshaft. I didn't have any trouble with fluid going anywhere, I guess because the rear was up on stands. You won't be running it very long anyway, so I'd try it. Also, my guess is that once you pull the driveshaft the fluid won't keep gushing out. It'll spew a little and then stop. This is a good indication that there won't be much, if any, fluid spraying around the garage.

[Old Goat Racer]

Originally Posted by Old Man Taylor

I'v had that problem twice. Once it was a bad pressure plate, the other time it was the drive shaft. I would be very surprised if your pinion angle would be causing a vibration that bad at a constant slow speed.

I have to agree with OMT, not pinion angle. I would look at the tranny bushing.

[pontiacmark]

Finally got to pull the axles last weekend out of both my GTO and a spare rear I had. The best axle had around .020" runout. One of the GTO's axles had over .060" and was twisted as well. I will be ordering new axles soon.

[pontiacmark]

Here's a low quality video that I took with my phone. Notice the amount of movement in the shaft at the end of the video while it is spinning in the lathe.
http://www.pontiactn.org/029.3g2

[pontiacmark]

Well, I finally saved up the money for the custom Moser axles and got them installed. Took the car out for a test drive and it STILL has the same vibration. I am PO'd to say the least. I am going to try and "re-phase" the driveshaft and see if that helps. Any other ideas?

Here are two other threads on the subject as well.

http://forums.maxperformanceinc.com/...ight=vibration

http://forums.maxperformanceinc.com/...ight=vibration

I have been fighting this for 9 YEARS and I am frustrated because I can't drive the car any distance.

[pontiacmark]

Thought I would resurrect this old thread and update things. Turns out the tailshaft bushing was shot. Had around 0.040" clearance between it and the yoke. Ended up going with the Keisler RS600 trans and I can now drive on the interstate without feeling like the car is going to come apart.

[Old Man Taylor]

I'm interested in your input on your new transmission.

[Lemans64]

Me as well, I am chasing vibration in my 64, new driveshaft, all u joints, new trans bushing, new adjustable upper arms, slowly seems to be getting better with more money, LOL. Did the new trans come with shorter driveshaft??

[pontiacmark]

OMT, love the transmission. Very easy to shift and quiet. With my 3.23 rear and 235/60R15's I am turning around 1900 at 70 mph. www.keislertv.com has the video of my car.

Lemans64, yes, the trans came with shorter driveshaft due to the increased length of the trans.

[Old Man Taylor]

That would make mine about 2400-2500 at 70. I currently have 4.33's with an M-22. The 2.20 first gear is pretty good, but it is still a challenge to keep the tires form spinning on a first gear roll. If I made this swap I would leave the gears alone, and then later drop them down. I no longer race the car, and the gears are REALLY low for driving on the freeway.

[pontiacmark]

Well, back to this issue, AGAIN. At first, the new Trans seemed to have made a difference but I still have the vibration at highway speeds. Since the new Trans required a new driveshaft, I thought I would check the angles again. Almost exactly the same as in post 21. I have the car on jack stands again and will try running it through the gears tomorrow and see what happens. Thoughts?

[wheneaglesfly]

Wow. This is a really old thread.
Dates back to 2008.

I have some ideas to share. Try out.
Collect my thoughts here.

[wheneaglesfly]

Ok.
Driveshaft angles are seldom an issue in Vintage cars unless the rear springs are severe sagged.
Ir a non stock rear differential was installed and a butcher job done.

[wheneaglesfly]

What kind of wheels are on your GTO ?
Tires being used ?
Lots of aftermarket Rims suck Azz.
China made.
Radial & lateral runout must be .050" or less.

Its a problem in the Corvette world.
5-star rims. ZR-1 Rim clones.
Chuna made.
Real deal checks out .005" tolerance .

[wheneaglesfly]

Centerlines, Weld Racing, Some Cragars are excellent .

[wheneaglesfly]

Lets find out if your GTO frame is Tweaked or not.
Measure the Wheelbase.
Drivers side.
Passengers side.
Car on the ground.
Center caps off the rims.
With a helper like your Wifee' measure with a Good tape measure.
From hub center to hub center.
Should measure within 1/8" .
1/4 Inch ok.

[Keith Seymore]

... Or - you could go back to the flow chart posted on page two.

If you can follow that thought process you can fix anything.

K

[pontiacmark]

Keith, I did revisit the flow chart. I do understand it as a mechanical engineer but can't understand why my angles are so far off with both the Muncie and the RS600. Back when I first checked the angles I did replace the motor mounts but still could not adjust the Trans mount high enough to make it close to parallel with pinion. Curious if could place accelerometers close enough to parts to find where it is originating from. I don't have a high speed DAS but maybe could borrow one.

As stated before, the wheels/tires were replaced with known good set. Rear springs were new 3000 miles ago along with all front suspension pieces and rear shocks. bushings on rear control arms were replaced at same time as axles.

I will check the wheelbase to see if the axle is tweaked one way or the other.

[Keith Seymore]

If you can come up with accelerometers that would be ideal.

You can place one accelerometer on the pinion nose of the rear axle (to measure vertical response) and order track the results. U joint issues will be second order of driveshaft rotation. It will provide a definite signature of the offending component.

You can also place accerlerometers on the seat tracks (or some other responding component) to more closely document what you are feeling.

That will also eliminate (with certainty) all the things it is not, so that you can focus on what it might be.

K