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Just had this occur last night. About 30 mph let off the gas and the rear kind of 'crabbed' to the right. Startled me at first. Nursed it home, jacked it up and checked everything I could think of and all seems perfect. So I went out again today and at most any speed it will noticeably crab when I let off the throttle. Accelerate, and it straightens.
I'm suspecting something going on with the differential. I'm going to change oil in it and see if any noticeable change. The diff is a rebuilt unit installed maybe 600 miles ago. 3:55 in a '71 350 5 Spd. Anybody experienced this?
Trailing arm bushings does makes sense. I am assuming they were done when the car was redone 20 years ago but maybe not. Or time has dried them out. There's less than 10k miles on them. Only way to know is to dig into it. Not a job I wanted! Thanks for the input.
a visual/ pics may tell you something, especially if broken out. OEM rubber sometimes looks ok and is not.. had same issue.. they may have used some poly chinesium as well.
The reason I initially suspected the rear diff had to do with an experience many many years ago in a fairly new 69 Chevelle that developed a weird habit of pulling hard right, (or left I forget which), under acceleration. That turned out to be low pressure in a rear tire that had picked up a nail. For some reason that always stuck as a peculiarity with posi attraction.
If the diff was the issue I would expect you would hear gear whine or clash. Spring load posi's are almost always out of balance, unlike a tuned posi. However, the level of differential work I see- having repaired so many over the years anything is possible. If you have pictures of the rebuilt diff I would be happy to check them for you.
Many years ago, I had a Corvette repair shop as a sideline business. A guy showed up with a '71, said it pulled to one side when accelerating.
I found the trailing arm had a vertical crack about mid-point. The crack was barely visible; however, the crack would allow the trailing arm to flex. The arm was very rusty.
Found it. Passenger side arm loose as a goose. With a flashlight, it looks like the bushing has completely failed. Guess my earlier inspection wasn't so good.
I'm pretty sure it was replaced when the car was redone. But apparently not a very good piece. Anyhow, off to the races. A job I never wanted to do. But the more I think about some of its habits, I have a feeling this is the source of a couple other weird noises and clunks along the way. Might as well redo the left side as well. Thanks again, guys and gals.
I've had in "rebuilt" TA where the bushings were not compressed and flared correctly. Also, never installed arms with poly bushings that crumbled and fell apart.
My 1968 C3 did the same crabbing down the highway when the road got wet during a torrential rainstorm (remnants of Hurricane Andrew, August, 1991). When I hit ~35 mph the rear went to the left a bit and it was very obvious that there was a problem. I was lucky as it happened while I was at Corvettes@Carlisle and Art of Van Steel was able to show me exactly what was happening that caused my car to crab. Needless to say the folks at Van Steel received both trailing arms in for a re-build.
The only hard part was trusting the car enough to drive it 103 miles back home after finding the crabbing issue. With no rain my C3 tracked okay, for some reason the rain made the issue worse.
I would remove both of your TA's and rebuild them together. Some like Gary (GTR1999) would be the ideal person to help you in a matter like this. Van Steel does awesome work as well and their turnaround was not bad when we rebuilt mine.
Yeah, that crabbing thing is a little startling when you're not expecting it! lol. So a couple things going on here. These trailing arms should have been redone back in 2000-ish when the car was rebuilt. Likely no more than 10,000 miles driven since. I'm hoping just this one bushing has failed and I'm kind of intrigued to do it myself. If it has to be redone and or the other side also fails at least I will be 'practiced' in removing and replacing the arms.
Removing the trailing arms is a job for lots of penetrating oil and a good sawzall with long blades to cut the bolts. I would also replace the shims in that area while you are at it. They are made in Stainless for those who are not fans of rust. I have seen them come out as chunks of steel.
I removed my TA's and shipped them off as I mentioned earlier. The job of rebuilding them seemed a bit "daunting" at the time and I was not sure I was ready for the job of setting one up. I have been a mechanic for over 50 years and am comfortable doing most jobs. After listening to Art from Van Steel explain the process to me it made more sense to just send the TA's to them. If I was going to have to do it again and again I would have tried it myself and learned how to do them properly. There are some special tools needed to help in the setting up of the bearings in the TA.
Finding out that I had a bad T/A was still one of the scariest drives in my life. I had never driven anything that crabbed like the car during the rainstorm. I don't know why the TA showed it's hand while raining but it sure made driving more like a skating experience and I was on the PA Turnpike!!
I wish you all the luck in the world in this next endevour! Lets us know how it goes!
Hey, that's just the thing. This thing is all nice and clean. The through bolt and shim and everything all look like new. So I don't anticipate much trouble getting it out. Just figured I'd wait for the parts to get here before I completely disable the car. Hope to report back by the end of next week.
Could it be that the shims were just loose?
FYI: I had a problem getting my trailing arm shims tight.
The sleeve was not crushed properly, and was not flat, and I had problems getting the shims tight, until I had the trailing arm re-done. Improperly crushed bushing sleeve, affecting shim fit.
Repaired and replaced bushing sleeve, properly crushed and flared, and very flat, with no protruding edges.
There are a couple of special tools to hold this bushing assembly compressed, while the center sleeve is flared in a press, with a flare tool.
I don't have it out yet. But from what I can see that might be the issue. Something about the shims doesn't look right. And the bushing is definitely separated. Thanks.
Rear Posi Peculiar Problem
