4th gen TA driveline vibrations...need advice
09-02-2009, 02:31 PM
#1
4th gen TA driveline vibrations...need advice 4th gen f-body driveline vibration help please....
--------------------------------------------------------------------------------
I got the car all put together and have been messing around working out all the bugs, but I am kind of stuck at the moment. I have some driveline vibration that I cannot seem to get rid of. This is a stock suspension (fully double adjustable rod end everything) 4th gen f-body. I added a th400 and Moser 9”, w/ a Strange chromoly 44 ¼” driveshaft that is 3” dia w/ 1350 u-joints.
I used a manual v8 tranny crossmember and 1” worth of spacers to bring it to the correct height. As of right now, the engine / tranny is pointed down 4 degrees, and the rear end is tilted up 4 degree. This is going in accordance with Rossler tranny info on their website. There is a vibration in the tunnel at 2400 rpm in every gear. Then it is smooth again. Then the vibration starts back up again, this time at the rear of the car, from 4000-6200 rpm. I set the lower control arms to stock length, and went from the outside of the quarter panels to the outside of the tires on each side until I got the rear end centered. If I let go of the steering wheel while driving, the car doesn’t wander or anything. Drives extremely strait. Just normal street cruising, the car drives smoothly and you wouldn’t notice the vibration at all. I have tried a bunch of different pinion angles and the numbers that I listed above appear to be the smoothest running.
Since this is a 9” rear, the pinion is also offset to one side also, which there isn’t any way to move it unless I move the panhard bar, which the rear is centered now, so there is no point.
Is it possibly the pinion angle? I was using an old GM service book that had info on driveline vibration. It said that if the vibration is there at the same rpm no matter what the gear, that it is not the driveshaft, so I guess I can rule that out. It also said that the u-bolts could be over torqued (I just snug them up w/ a box wrench), tires could be out of balance, etc. I would think that I would feel a vibration all the time if it was the tires out of balance though.
=================================================
Before I would get a vibration in the tunnel at 2400 rpm in each of the 3 gears. Now it is gone in 1st, almost non existant in 2nd, but still there in 3rd.
(since I made them match both at 4 degrees)
Then at 4000-6200 rpm, it would vibrate pretty bad at the rear, now it has quieted down, but it won't stay consistant. The vibration starts and stops very quickly and acts like a radio station cutting out.
I tried measuring the face of the axles with a dial indicator, but my readings were always getting messed up because while I turned the axle, depending on how much force I applied, the axle would move in our out a few thousandths. So I canot use this info. But I would think that if an axles was bent, I would feel it all the time.
I have tried the pinion angle at 1 and it was bad, at 0 it was horrible. I never tried it at -1 though. From what I read, the angles should never vary more than 3 degrees. But I will try almost anything.
Anyone have any ideas of other things to check? The car won’t be taken to a shop for anyone to work on, so that is not an option, lol.
Any advice is greatly appriciated
I apologize ahead of time for my awesome paintbrush skills
Thanks
Mark jr.
--------------------------------------------------------------------------------
I got the car all put together and have been messing around working out all the bugs, but I am kind of stuck at the moment. I have some driveline vibration that I cannot seem to get rid of. This is a stock suspension (fully double adjustable rod end everything) 4th gen f-body. I added a th400 and Moser 9”, w/ a Strange chromoly 44 ¼” driveshaft that is 3” dia w/ 1350 u-joints.
I used a manual v8 tranny crossmember and 1” worth of spacers to bring it to the correct height. As of right now, the engine / tranny is pointed down 4 degrees, and the rear end is tilted up 4 degree. This is going in accordance with Rossler tranny info on their website. There is a vibration in the tunnel at 2400 rpm in every gear. Then it is smooth again. Then the vibration starts back up again, this time at the rear of the car, from 4000-6200 rpm. I set the lower control arms to stock length, and went from the outside of the quarter panels to the outside of the tires on each side until I got the rear end centered. If I let go of the steering wheel while driving, the car doesn’t wander or anything. Drives extremely strait. Just normal street cruising, the car drives smoothly and you wouldn’t notice the vibration at all. I have tried a bunch of different pinion angles and the numbers that I listed above appear to be the smoothest running.
Since this is a 9” rear, the pinion is also offset to one side also, which there isn’t any way to move it unless I move the panhard bar, which the rear is centered now, so there is no point.
Is it possibly the pinion angle? I was using an old GM service book that had info on driveline vibration. It said that if the vibration is there at the same rpm no matter what the gear, that it is not the driveshaft, so I guess I can rule that out. It also said that the u-bolts could be over torqued (I just snug them up w/ a box wrench), tires could be out of balance, etc. I would think that I would feel a vibration all the time if it was the tires out of balance though.
=================================================
Before I would get a vibration in the tunnel at 2400 rpm in each of the 3 gears. Now it is gone in 1st, almost non existant in 2nd, but still there in 3rd.
(since I made them match both at 4 degrees)
Then at 4000-6200 rpm, it would vibrate pretty bad at the rear, now it has quieted down, but it won't stay consistant. The vibration starts and stops very quickly and acts like a radio station cutting out.
I tried measuring the face of the axles with a dial indicator, but my readings were always getting messed up because while I turned the axle, depending on how much force I applied, the axle would move in our out a few thousandths. So I canot use this info. But I would think that if an axles was bent, I would feel it all the time.
I have tried the pinion angle at 1 and it was bad, at 0 it was horrible. I never tried it at -1 though. From what I read, the angles should never vary more than 3 degrees. But I will try almost anything.
Anyone have any ideas of other things to check? The car won’t be taken to a shop for anyone to work on, so that is not an option, lol.
Any advice is greatly appriciated
I apologize ahead of time for my awesome paintbrush skills
Thanks
Mark jr.
09-02-2009, 02:39 PM
#2
Your pinion angle is out of adjustment. First i would index the rear ujoint 180 degrees then make sure that you don't have the u joint caps too tight. Here is a link to a video that we made on the proper way to set your pinion angle. You want a total of -2 to -3 degrees. If you have any questions after watching the video give me a call. I can step you through the adjustment process. Its easier to explain it over the phone. I am in the office until 5:30pm est.
http://www.bmrtvonline.com/video_detail.php?mId=3788
http://www.bmrtvonline.com/video_detail.php?mId=3788
09-02-2009, 06:15 PM
#3
Your pinion angle is out of adjustment. First i would index the rear ujoint 180 degrees then make sure that you don't have the u joint caps too tight. Here is a link to a video that we made on the proper way to set your pinion angle. You want a total of -2 to -3 degrees. If you have any questions after watching the video give me a call. I can step you through the adjustment process. Its easier to explain it over the phone. I am in the office until 5:30pm est.
http://www.bmrtvonline.com/video_detail.php?mId=3788
http://www.bmrtvonline.com/video_detail.php?mId=3788
What he said!!
I had some issues also, until I adjusted my torque arm as their video instructs. Now it's A-OK!!
09-02-2009, 10:28 PM
#4
Your pinion angle is out of adjustment. First i would index the rear ujoint 180 degrees then make sure that you don't have the u joint caps too tight. Here is a link to a video that we made on the proper way to set your pinion angle. You want a total of -2 to -3 degrees. If you have any questions after watching the video give me a call. I can step you through the adjustment process. Its easier to explain it over the phone. I am in the office until 5:30pm est.
http://www.bmrtvonline.com/video_detail.php?mId=3788
http://www.bmrtvonline.com/video_detail.php?mId=3788
I will be giving you a call tomorrow with some questions concerning the adjustments since I no longer have stock ride height (due to tire and rim change) and since the engine isn't at the factory setting (used a v8 manual crossmember w/ spacers when swapping in a th400)
thank you for your response
mark jr.
