[Hurst65]

I'm sure he probably did but, did he recheck the runout after welding it up to make sure that it was still within limits??

Do the caps on the U-joint fit nice and snug into the pinion yoke? With the shaft bolted into the pinion yoke can you grab it and move any at all side to side in the yoke? It is possible that the "little ears" on the yoke may be worn.

If the shaft was properly balanced (I'm sure it probably was, it looks like he has a nice machine) then I wouldn't waste any time messing around with it. The problem is probably somewhere else.

[andrewb70]

Originally Posted by Hurst65

I'm sure he probably did but, did he recheck the runout after welding it up to make sure that it was still within limits??

Do the caps on the U-joint fit nice and snug into the pinion yoke? With the shaft bolted into the pinion yoke can you grab it and move any at all side to side in the yoke? It is possible that the "little ears" on the yoke may be worn.

If the shaft was properly balanced (I'm sure it probably was, it looks like he has a nice machine) then I wouldn't waste any time messing around with it. The problem is probably somewhere else.

The pinion yoke doesn't have that many miles on it. The u-joint fits very tightly between the little tabs. When Terry made the driveshaft he did in fact check the runout after welding it. In the rear it was very good, .002". I am running out of ideas.

Andrew

[Silver Judge]

Nice job on this engine swap and all of the re-engineering you've done Andrew

Yeah, it would be cooler with a pontiac engine in my opinion but you've built a helluva nice driver here.

Good luck on the vibration, keep us posted on that and how those new spindles turn out, those are supposed to be some pretty nice pieces

[Z Code 400]

Andrew,

I have seen the 'straps' stretch and allow the U-Joint to 'float' even though the bolts are tight. I'm not sure if you have U-Bolts or Straps, but it could be worth looking into.

When we were building V8 Vegas, I encountered one with a similar vibration. We just couldn't figure it out. After a while, I just laid under the car during lunch and pondered the problem. I discovered the driveline was out of alignment laterally. In the case of this car, the frame brackets were off by a mile from the factory and the unibody wouldn't have survived cutting them off and re-welding. We just moved the upper and lower perches to shift the axle centerline.

Probably not a problem in your car, but you could have an off-center yoke on the rear axle???...Robert

[andrewb70]

Originally Posted by Z Code 400

Andrew,

I have seen the 'straps' stretch and allow the U-Joint to 'float' even though the bolts are tight. I'm not sure if you have U-Bolts or Straps, but it could be worth looking into.

When we were building V8 Vegas, I encountered one with a similar vibration. We just couldn't figure it out. After a while, I just laid under the car during lunch and pondered the problem. I discovered the driveline was out of alignment laterally. In the case of this car, the frame brackets were off by a mile from the factory and the unibody wouldn't have survived cutting them off and re-welding. We just moved the upper and lower perches to shift the axle centerline.

Probably not a problem in your car, but you could have an off-center yoke on the rear axle???...Robert

Robert,

When I got the new driveshaft made I actually picked up a set of new straps.

I believe a-bodies had the engine centered, but the pinion is offset slightly to one side. As long as both the pinion and output shaft point straight back (as viewed from the top) then everything should be OK. How would I even go about checking that? :/

This sucks. I am running out of ideas. The car is up on 4 jack stands right now and I am trying various pinion angles and nothing seems to make much difference. The car starts to vibrate at right around 2200 RPM driveshaft speed, regardless of what gear it is in.

I tried hanging hanging hose clamps at the back of the driveshaft in order to see if I can make a difference, but that seemed to make things worse. I clocked the heavy sid of the clamp so it was on the light side of the pinion yoke.

If I knew that throwing money at it would fix it, I would do it. I just don't know what to replace.

Andrew

[Z Code 400]

Andrew,

Some leteral offset is OK, but our Vega was substantial; to the tune of almost 1" overall. We verified this by super gluing string to the crank snout, gearbox output and pinion shafts, making 'plumb bobs' with castle nuts. We then placed a string through the nuts and tied it between two brake drums.

Once the engine/gearbox were on-center, moving the differential was easy. However, I don't think this is the problem with your car.

We had a customer's car with a similar vibration and we discovered it was the exhaust system causing it. The pipes were completely rigid and when we unbolted the exhaust and let it hang loosely, it went away completely.

If you had .002" runout on the bench and .0038" in the car, could you have a improperly machined U-Joint????....Robert

[Hurst65]

Driveshafts are assembled, welded, and balanced with the u-joints in place.

Is the pinion itself loose??

[andrewb70]

Originally Posted by Hurst65

Driveshafts are assembled, welded, and balanced with the u-joints in place.

Is the pinion itself loose??

That is correct. The driveshaft was assembled and checked with the rear u-joint in place.

There is no noticeable play in the pinion. The rear end was gone through by a good friend of mine who is an excellent mechanic and engineer. The pinion yoke is off a bit, but I did the hose clamp test to try and offset the imbalance and it made zero difference. It just seems like nothing I do makes that big of a difference.

Robert,

I was really hopeful that your exhaust theory would pan out. My exhaust is anchored very firmly and I thought that might be it. So I loosened the hangers that attached the exhaust to the frame, just in front of the rear axle, and there was no change at all.

The next step I am tempted to do is support the frame in the rear and put a jack under the rear end. Then position the rear end to simulate stock ride height dimensions, God knows what those are, and see if that makes any difference.

I wish I had a spare rear end or transmission around for testing :/

Andrew

[Hurst65]

I'm a little confused...what do you mean by "the pinion yoke is off a bit"?
Are you saying that it looks like it was machined off center or that it has been "tweaked" somehow? If that is the case and it is causing the runout on the shaft to increase that much, it would be next to imposible to balance the drive shaft or would atleast require alot of weight to do so.

Also, if you are running the car on stands the rear should be at normal ride height. If the rear is just hanging down the working angles on the joints will be increased and may contribute to your vibration issues.

Hope this helps!!
Eric

[andrewb70]

Originally Posted by Hurst65

I'm a little confused...what do you mean by "the pinion yoke is off a bit"?
Are you saying that it looks like it was machined off center or that it has been "tweaked" somehow? If that is the case and it is causing the runout on the shaft to increase that much, it would be next to impossible to balance the drive shaft or would atleast require alot of weight to do so.

Also, if you are running the car on stands the rear should be at normal ride height. If the rear is just hanging down the working angles on the joints will be increased and may contribute to your vibration issues.

Hope this helps!!
Eric

Eric,

Thanks for the help. The car is supported under the frame in the front and on the rear axle in the rear. So it is at ride height.

The pinion yoke does indeed look like it is machined off center. At this point that seems to be my main culprit.

Andrew

[Hurst65]

Okay...
If the pinion yoke is not machined right and it is causing the runout at the rear of the shaft to be off as much as you say it is, then I would say that is your problem. That would be really werid if that was indeed the problem but, I suppose that it is possible. With the runout being off that much on one end of the shaft it would take alot of weight to even begin to make it balanced (if at all possible).

It would be nice if you had another pinion yoke to swap in there and see what happens...

Sweet car BTW!!! Hope you get it worked out!!

Eric

[andrewb70]

I got the wheel centers back today and they look pretty amazing.



I should have the polished rims tomorrow and then I can start on assembling the wheels.

During a recent trip to Chicago I stopped by The Parts Place and picked up a new pinion yoke. After installing it, I measured the run out and it was .004", quite a bit less than the run out on the other yoke which was about .040". I ran it up to speed on the jackstands and it was very smooth in 5th gear (1:1) all the way up to 4500 RPM. It still vibrated a little in 6th, but I think most of that is due to the fact that there is no load on the driveline. I am going to leave it for now and see how it feels going down the road.

The brakes should be here next week, then I can be back on the road.

Andrew

[mzbk2l]

Wheel centers look great! Sounds like you're getting on top of the vibration, too.

[andrewb70]

At 4pm this afternoon I showed up at the polisher's place and the wheels were done, as promised. I have to admit the results were better than I imagined. This guy is simply amazing. His name is Jeff Smith and it turns out he did all of the brushed aluminum work on Bob Johnson's Cuda. I am pretty sure that they weren't this nice when I first got the wheels. I got them home, masked off the front, and spray painted the inner hoop silver. I figured that having a painted inner rim will be easier to clean than a plain aluminum one. After painting I applied a generous coating of wax to the polished surface to seal them a little bit. After that it was time to assemble the wheels. I lined up the center according to the marks that I made before taking the wheels apart. This way the wheels go together exactly the same way with the center going back to its rim. I used a little anti-seize on the splined section of the bolts and drove them through the center and the rim. Then I flipped the wheel over and started torquing the nuts in a star pattern. It took about 2 hours to do one wheel but the results were well worth it. It's like a brand new wheel!







The little notch marks on the back are to keep track of the torque sequence. With 40 nuts to tighten, it is very easy to loose your place.

Andrew

[andrewb70]

Today I assembled the rest of the wheels and had the tires mounted. I am very impressed with the Falken tires. Neither front wheels needed any weight. One rear tire needed .75 oz while the other balanced with only .50 oz. That is very impressive considering the size of the tires.

Andrew

[andrewb70]

Teaser shot of the wheels on the car.



Andrew

[Hurst65]

Sweet!!!

[andrewb70]

This morning I got my brake components from Kore3. Tobin at Kore3 has outstanding customer service and I am very pleased with the parts. I got C6 Z06 calipers, 14" DBA 4000 rotors, and Hawk HP Plus pads.



More pictures to come.

Andrew

[andrewb70]

I drove it again this evening. In the morning I am going to get an alignment. The C6 Z06 brakes are very nice. I really like how the ATS spindles work with the OEM style brakes. Everything bolted together beautifully.







The car is sitting a little higher in the front now. This is due to the fact that my old spindles had a 2 inch drop compared to stock. I believe the ATS spindles are about an inch lower than stock. I was going to lower it, but I think I am going to keep it this way. It's nice not having to worry about any sort of rubbing with the tires. I also think that the springs will settle some over the winter.

Andrew

[mzbk2l]

That thing must be a blast to drive now. I've had my eye on kore3 parts for some time now, but they just seem like such overkill compared to the rest of my stock ride.