Posted a thread a while back about something weird on my '89.
Hit the gas hard, the car goes left.
Let off the gas, the car goes right.

Bounce the pedel and you can feel the back of the vehicle shifting around.

Wise forum memebers said to replace the "dog bone" bushings, so I went in and did all the rear bushigs sans sway bar and bat wing.

Problem is still there. It feels like the whole rear of the car is loose!

Tie-rods look ok. Had the aligmenent checked before the bushings, and it was in spec. I know it needs another check after the bushing install, but I dont think this is alignment. You can feel something is sloppy.

Any ideas? Tranny mounts? Help!!

 

broken motor/t'mission mounts ? Add a little right rudder to counteract the torque. Whoops wrong forum .

 

I hope you didn't change those bushings on my say so, without checking them. The car is being steered by the throttle. The first thing that comes to mind, is alignment that changes depending on the forces acting on the rear tires. When you are on the gas the engine is driving the car. When you are off if the gas, the car is driving the engine. Bad dog bone bushings could very easily allow the wheels to shift position, depending on the application of power, and steer the car. The sway bar bushings would have no effect, but the batwing bushings could. Another thing to check would be the condition of your posi traction. Maybe you have some serious rear frame issues.

RACE ON!!!

 

Yes and no. I have two vettes, I don’t drive either much. So working on it is not a big deal. And lord I need to learn the patience! Broke a shock bolt off in the frame and had to drill and tap it! Pain!!

The camber strut bushings on one side looked really bad.
The rest were give and take. Some were a little disfigured, others looked fine. I thought what the hell, its 17 years old, and for ~$150.00 and several hrs, it's done. Plus it keeps me entertained.
Just bummed it didn’t fix the problem. Thanks a ton for the suggestion though. It sure looked like it would be the problem.

Changed the dif. fluid a while back. The posi-traction seems to be ok. There is definitely something shifting around though. I would not expect the dif to make the whole car shift like it does. I would expect the dif to be more of a pull to one side or the other. Batwing bushings sounds possible, but they looked pretty good. And the amount of wiggle I feel in the drivers seat seems way to much. It feels like dog bone bushings are missing on one side!

Frame issues? What you mean? I’m the original owner. How can I check for a fame problem? Wouldn’t I have to hit something to screw the frame up that bad?

There is a large frame member that goes from the front to back along the propeller shaft. Could this be lose or something? Any suggestions are greatly appreciated!

 

By frame issues, I mean broken somewhere, or something that has become detached. A bent frame wouldn't cause the change in the "rear steer" you are experiencing. Something back there is loose and allowing movement. It COULD be as simple as wheel bearings. How are the tie rod ends?

I have a 4X4 pick up with a Detroit (Locker) Automotive No Spin in it. The nature of that diff is that no rear wheel can rotate slower than the ring gear. Under normal, straight ahead conditions The truck is being driven by the right rear wheel. When I take my foot off of the gas, the engine braking is through the left rear wheel. I haven't checked the rear suspension on the truck, but it definitely steers with the throttle. If I take my foot off the gas to slow down, I have to correct the steering with the steering wheel. If I step back down on the gas, the same thing.

RACE ON!!!

 

If it wasnt for the weird shift I feel in the seat, I would say its like your 4x4. But I can feel something move. It alsmost feels like the body shifting on the frame, but I know they are attached.

Tie-rods looked ok in the back. Havent looked at the front in a while.
Thought of a bad bearing last night, and was pulling hard on the tires while the car was on the jack to see if I could get any movement out of them. Bearings seem ok.

I'll get it on jack stands this weekend and get all the way under it to see if I can see anything. Whatever it is, its gonna be interesting when I find it......Thanks for the ideas.

 

I had the same problem with my 86. I found a bad rear tie rod end.

 

Rear tie rod failure would be my first guess. Just because they 'look' ok doesnt mean they are, you could try jacking the rear up and grabbing at 9-3 o'clock, if theres movement then it would indicate they're the problem.

movement at 12-6 would show bearings

 

I had the same issue with my 92. What I found was that the people who had been aligning the wheels for me were not doing something right. I took a tape measure, and measured from the wheel to a common point on the rear end on both driver and passenger sides, and compared the two. I found that the passenger side of my car was had a toe - in about 1/2" more than the drivers side. I just adjusted the rear tie rods to make the passenger side the same, and now the "shift" is gone. You might try taking the car to another place to have it aligned, I am sure mine is somewhat off. Just another item to check...

Chris

 

Thanks guys.
I’ll keep digging.
Cant seem to figure this out.
Cant find anything that looks really bad, but something is certainly weird.

I’ll double check Tie-rods and have a different shop give it an alignment.

Thanks for the suggestions.

 

Don't forget that the rear tie-rod assembly has pivot points in the middle where it attaches to the differential -- these can wear/break too.
Don't only look at the outer tie rod ends at the wheels.

Tom Piper

 

Make sure the C-beam bolts are tight

DS