Car steers to left when accelerating

[George W.]

I have a 73 LS4 four speed corvette that was restored in 2013. Had it judged a couple of times and then stored it. I have recently decided to drive the car more and have noticed a slight steering to the left under acceleration and slight steering to the right under deceleration. Any thoughts on what is causing this?

Thanks for any help.

George Walker

[Bill W.]

Re: Car steers to left when accelerating

George,
Swap the rear tires and see if the condition you describe reverses. Also check tire pressure. I am assuming, and you know what that means, that a competent alignment shop has had it's hands on the car. Bill

[George W.]

Re: Car steers to left when accelerating

Thanks for your response. Tire pressure is equal on both sides, tires have less than 200 miles (Kelsey reproduction). Alignment was done in my shop with strings and levels. May not be correct but there are no shops in my area I trust. The car appears to track true, with no pulling right or left when cruising. It is only when accelerating (fairly hard) that is steers slightly left and then slightly right when decelerating.

Trailing arms were done by Bairs, and shim packs are tight. It acts like some thing is moving. If it were a straight axel I would think a spring shackel was loose.

[Patrick B.]

Re: Car steers to left when accelerating

It's still worth swapping rear tires before digging deeper. I almost didn't buy my 70 LT-1 (that I'm glad I still have) in 1972 because it did the same thing. The owner swore the car had never been wrecked and agreed to swap the new offbrand rear tires. As soon as he did, the car began pulling to the other direction under acceleration, so I believed him and bought the car. The reproduction tires today may have the same quality control problems that offbrand tires had in the past.

[George W.]

Re: Car steers to left when accelerating

Thank you. I will switch them tomorrow. Will get back with results.

[Michael W.]

Re: Car steers to left when accelerating

Lost trailing arm shims or a failed trailing arm bushing will allow the front of the arm to move laterally, giving you the effects described.

[Rich G.]

Re: Car steers to left when accelerating

I second what Michael says. Not exactly the same but I bought a brand new 1970 MGB and it did the same thing. It turned out the rear suspension had never been torqued at the factory. Talk about quality control.

[Duke W.]

Re: Car steers to left when accelerating

Thank you. I will switch them tomorrow. Will get back with results.

While you're at it measure the circumference of each tire with a tape measure. If there's more than one to two percent difference, that could be the cause.

... understand your concern about commercial alignment shops. I gave up on them over 30 years ago. They have wonderful equipment, but the operators rarely understand suspension geometry or "performance alignment".

With the IRS it's tough to get the rear toe-in equal on both sides with simple equipment. I did mine be measuring the centerpoint at all the cross members, then ran a string with plumbobs along the centerline to measure/equalize each side toe relative to centerline, but that was with the body off the frame and the spring not attached with the rear suspension supported to nominal ride height.

It's tougher with the body on.

Duke

[George W.]

Re: Car steers to left when accelerating

Thank you all for the responses. I examined the trailing arm shims closer this morning and found the left side loose. I added a 1/32 shim and torqued to specs. A test drive indicated no left steer on acceleration very slight right steer under deceleration. Normal driving and slowing did not show either. I think the loose shim pack was the problem. I will measure the circumference of each tire.

When preparing for alignment I studied the posts in the archives, down loaded some papers on the subject and felt comfortable following the advise from these sources. I had not noticed any issues under normal driving conditions but have just recently began to push the car harder. That's when this condition was noticed.