Swerve on acceleration

[wood8835th]

Getting some squirrelly behavior in rear end of 75 vette. Not sure whether to evaluate differential (Posi) or alignment/strut rod/bushing. Anyone have any advice on discerning which one I should attack first. Or something different?
Just started in last week

It appears visually that camber on left wheel is off (at least compared to right). Base of tire seems farther out than top. Checked adjustment bolts and they seem snug with no evidence of recent movement. Bushings may be original, at least they look like it. Shocks are in good shape. When going over potholes or roughness in road (not done on a routine basis) rear end drifts right. Same on acceleration. Rear end feels sloppy. Diff oil level and color good.

Any advice?

 

[WayneLBurnham]

Not specifically.....after losing a wheel, I always worry about rear bearings....

but that doesn't sound right here.

If you can see something visually misaligned, then $60 at the alignment shop is called for right off. While it's up on the rack if you've never changed the fluid, do so with nice good high dollar synthetic and a couple of tubes of the posi additive first. (It hardly sounds like it's a diff issue though.)

The first thing to look at is anything that is causing such a visible misalignment. Since it's so far off, it's going to need aligning anyhow - they might see something much more easily when it's up on the rack than you have on the ground (and it's less likely to squish you like a melon when it wobbles off the jack stands when you're pulling and whacking on suspension parts....I hate that when that happens! ) This is even better if you have a decent vette specialty shop near you as opposed to a regular alignment shop.

 

[78SilvAnniv]

While it is in the air, and before they perform the alignment, you will need to have an experienced mechanic determine if the side yokes are functioning properly. Why pay to align it if that won't fix the initial problem? Check for in/out play.

Do check to see if it is something easy, but chances are this could be the sign of a deeper problem. Better to find out now before you throw good money away by not fixing the source of the problem.
Heidi

 

[74bigblock]

Before taking it anywhere... jack up that side of the car and try to wobble the tire/wheel up/down (Check for bad T-arm Bearings). If it moves more than 1/8 inch... you have bad T-arm bearing or bad Ujoints or both.

 

[Hib Halverson]

Ok, the symptom is the car "steering" without steering input when you accelerate hard. Some call this "toe steer" and it occurs when torque application causes some part of the rear axle mounting or rear suspension to deflect in a manner that causes the rear wheels to steer the car.

The first thing I'd do is get the back of the car up on jack stands and inspect all the suspension parts, paying close attention to rear axle cross member mounts, rear axle cushions, trailing arm bushings, strut rod bushings, stub axle end-play and rear bearing play. If you find anything abnormal there, I'd make the appropriate repairs then have the rear end aligned.

 

[JohnZ]

Look for missing toe-in shims on either side of the trailing arm front bushings; that lets the front of the trailing arm move laterally, which changes toe-in during accel/decel.

 

[Blitz]

Same issue w/ my 81. It actually gets more pronounced as the suspension 'warms up'. Specifically, if Im cornering a bit aggressively, weaving in traffic, or repeatedly 'goose' the throttle.. the back end shifts consistently, predictably while accelerating and back while decelerating.

Bushings are original and are about to be replaced w/ poly. The right rear wheel is also further in under the wheel-well than the left. To my inexperienced eye, the stub-axles looked the same at the differential and I couldn't generate any play by shaking the wheel.

Its new to me, so an experienced vette mechanic is going over it... should have some answers back soon.

I'll be checking in to see what happens. Good Luck!

Blitz :confused

 

[dk1977]

I had the same problem you described. It turned out to be a bad right t-arm bushing (completely worn out). After removing the shock and the strut, the arm would literally wobble side to side rather than just pivot up and down on the bolt. If one is bad the other might not be far behind.

 

[smooth-rider]

Look at the shims for the trailing arm as I have the body off my 81 I can see that there's not much let of them. In the process of ordering new shims. this would definatly cause the car the sway.