Tailshaft vibration
Thread Starter
Pro
Joined: Jan 2004
Posts: 535
Likes: 1
From: Darwin, Australia NT
Tailshaft vibration
Not a corvette problem but I thought I would ask here as there has been a few issues with tremec installations where incorrect alignment (gearbox too low) induced a vibration. In these cases would the vibration be at all speeds or just a narrow band?
The reason I ask is a friend has put a TH 700 in a non corvette car that originally came with a PG. He has a bad vibration that occurs at 50mph but goes away at 60 (in gear or neutral). Im guessing its tailshaft (questionable supplier) but it also could be incorrect drive train alignment.
By the way my Tremec install displays no vibration but Ive got a real seal leak that appears common.
The reason I ask is a friend has put a TH 700 in a non corvette car that originally came with a PG. He has a bad vibration that occurs at 50mph but goes away at 60 (in gear or neutral). Im guessing its tailshaft (questionable supplier) but it also could be incorrect drive train alignment.
By the way my Tremec install displays no vibration but Ive got a real seal leak that appears common.
Burning Brakes
Joined: Dec 2003
Posts: 1,004
Likes: 7
From: Adelaide South Australia
Narrow band of resonant vibration.... like a slow repetitive wave every second. No vibration below or above that 5 mph band.
I too thought it was tail shaft balance, and had it redone.
No improvement.
After measuring my uni-joint angles on the tail shaft, incorrect alignment of trans to diff was considered main cause as I could not raise the rear of the trans high enough.
As a temporary measure to identify the cause, I placed a tapered plate between the diff and the diff mount to improve the alignment angles and it has eliminated 95% of the issue I had.
Now that I have confirmed that, I'll drop the box out and modify the trans tunnel / firewall to get the gearbox up to correct height when I find some time.
There is plenty of good info on correct driveline angles... do a search.
In essence, the gearbox output shaft and the diff input pinion need to be parallel to each other, and the uni-joint angles at either end of the tailshaft need to be equal in angle, but opposite in direction. Angles should no more than 3 degrees max
Zero angle is not considered ideal either, there should be at least 0.5 degree angle .
Hope this helps.
Instructor
Joined: Jan 2012
Posts: 201
Likes: 0
From: some hole in the ground town- camp verde:) arizona
considerin it happened when puttin a totally different trans in then wut the car came with i'd check the trans mounts. my car had/has this problem. it has a thm350 from the late 80's that doesn't fit properly. they used a thick piece of steel n cut holes in it n put some bolts through to bolt to the trans n ran it about 6in back to the mount n put bolts in there. the problem was this raised the trans too high n caused the driveshaft to rub against the body. i've put in a shorter mount but the problem is still there when hittin bumps or when there's a passenger or a lot of times at highway speeds. it seems to get worse the faster i go.
