Rear end shudder
Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 884
Likes: 84
From: New Boston, NH
Rear end shudder
This weekend I replaced my Trailing Arms and installed new adjustable strut rods. After getting everything back together, I took the car out for a drive to shake out any issues. I definitely noticed an improvement that good TA bushings make, but after a few miles, I noticed a new issue. When starting from a stop (red light), I get a very strong shudder in the rear end. Once up to speed, it smooths out. Also got the car out on to the interstate and accelerating up to 70 MPH did not produce any shudder. I don't recall this happening before the rear end rebuild, but I probably only had 5 miles on the car before that anyway. Regardless, here is a little more information that may be relevant in diagnosing the issue. U joints have been replaced, but this was done quite a long time ago. The rear end was swapped out after the original was deemed too far gone to rebuild. I bought a rear end with 3.55 gears from a forum member. Again, this was done several years ago. Car is a 75 with a 4 speed. I have not checked the diff fluid but will as soon as I can get the car up on jack stands. Any help you can all give would be greatly appreciated as well as any guidance on what to look for while under there.
Thanks,
Bryan
Thanks,
Bryan
Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 884
Likes: 84
From: New Boston, NH
If you are referring to the pinion snubber cushion, yes, that has bee replaced.
This project stalled on multiple occasions and the rear end was installed quite a while ago, probably 5 years or so. I cannot say with absolute certainty that I checked the fluid before installing, but my best guess is that I did not.
Thanks,
Bryan
Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 884
Likes: 84
From: New Boston, NH
Team Owner
Joined: Mar 2002
Posts: 44,682
Likes: 1,830
From: Huntsville AL
I would shudder to guess what is going on back there. But to shudder is to tremble with a sudden convulsive movement.
So assuming something is moving back there and based on your post all you really did was replace trailing arms installed new adjustable strut rods. Assuming the u-joints are good I would re-verify that everything is connected, shimmed and torqued as required.
Sounds like something is moving back there when it shouldn't.
So assuming something is moving back there and based on your post all you really did was replace trailing arms installed new adjustable strut rods. Assuming the u-joints are good I would re-verify that everything is connected, shimmed and torqued as required.
Sounds like something is moving back there when it shouldn't.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
some of these solutions are good ideas but they do not address what has changed?.. if it did not shudder before with old fluid, why would it shudder now?
my guess is that your ujoints were not replaced correctly when you put it back together, and are out of line. sometimes one or more of the needle bearings will fall into their cup and then the ujoint cup will not fit correctly. creating an out of balance situation in the half shafts.
it is easy to mess up, I have done it before.
but it should get worse with speed, which you say it doesn't.
my guess is that your ujoints were not replaced correctly when you put it back together, and are out of line. sometimes one or more of the needle bearings will fall into their cup and then the ujoint cup will not fit correctly. creating an out of balance situation in the half shafts.
it is easy to mess up, I have done it before.
but it should get worse with speed, which you say it doesn't.
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Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 884
Likes: 84
From: New Boston, NH
some of these solutions are good ideas but they do not address what has changed?.. if it did not shudder before with old fluid, why would it shudder now?
my guess is that your ujoints were not replaced correctly when you put it back together, and are out of line. sometimes one or more of the needle bearings will fall into their cup and then the ujoint cup will not fit correctly. creating an out of balance situation in the half shafts.
it is easy to mess up, I have done it before.
but it should get worse with speed, which you say it doesn't.
my guess is that your ujoints were not replaced correctly when you put it back together, and are out of line. sometimes one or more of the needle bearings will fall into their cup and then the ujoint cup will not fit correctly. creating an out of balance situation in the half shafts.
it is easy to mess up, I have done it before.
but it should get worse with speed, which you say it doesn't.
Thanks,
Bryan
Thread Starter
Burning Brakes
Joined: Jan 2010
Posts: 884
Likes: 84
From: New Boston, NH
HI all,
It has been two weeks since this post and wanted to circle back and close the loop. I finally managed to get the diff fluid changed out. The old stuff was pretty dark, and the level was probably near 1/4 to 1/2 inch below the plug level. Got 4oz of additive and just under two quarts of diff fluid put in. Got the car out yesterday, drove for a little while to get temps up then did about 20 figure 8s in the local middle school parking lot. I had the noise during the first 1 or 2, but by the end, smooth as silk. The fluid change seems to have done the trick. Thanks to all for the input.
Bryan
It has been two weeks since this post and wanted to circle back and close the loop. I finally managed to get the diff fluid changed out. The old stuff was pretty dark, and the level was probably near 1/4 to 1/2 inch below the plug level. Got 4oz of additive and just under two quarts of diff fluid put in. Got the car out yesterday, drove for a little while to get temps up then did about 20 figure 8s in the local middle school parking lot. I had the noise during the first 1 or 2, but by the end, smooth as silk. The fluid change seems to have done the trick. Thanks to all for the input.
Bryan
