Car twist

[HOTSIX]

I have a wierrd suspension related issue...

My 85 GN has all new suspension components up front and rear. I have replaced the rear with a posi unit out of a Cutlass or Monte or Buick - not sure. I have also removed the anti-roll bar in the rear with plans to re-install it. I have also installed boxed control arms in the rear.

When I drive down the road the car drives pretty straight. Upon even the slightest acceleration the car twists or rotates to the right. So much so that I have to compensate by steering to the left!

When I lift the throttle the car then deviates back to the right! I'm talking even the slightest acceleration here.

Again I have to compensate by steering inputs to the left or right when I am on the gas or off.

What the heck is causing this???

 

[Gary Wells]

Probably omitting the rear sway bar. How are your motor mounts?

 

[notacarlo]

I think you answered your own question with the sway bar removal.

 

[jdpolzin]

Why did you take the 8.5 out to install a 7.5??? Thats a bad move right there. But your problem is do to removing the rear swaybar.

 

[turbofish38]

How can this be a sway bar problem? Plenty of G-Bodies without sway bars out there.

Since you did some front end work I'd be looking there. Sounds like some serious bump-steer there if you ask me. How's the front end alignment and what specs did they use? What type of wheels and tires? How stock is the rebuild? Lots of questions before we can find a probable souce of the problem.

 

[HOTSIX]

Sway bar

Okay guys I figure I will just install the sway bar and see whats what. Dont get me wrong its not a 7.5 - its still an 8.5 just w posi...I just wasnt sure what it was out of. I remember checking the numbers on it and not being clear what exact car it was from.

My motor mounts are brand new and healthy - they were replaced 4 yrs ago and I havent had much driving since. Its a bit of a garage queen if you will.

I need to drill holes in the boxed control arms I installed and then stick it in. I also have not had a front end alignment yet either...although the garage that checked things over while installing a new rear main seal for me said it was 'pretty close' - whatever that means.

SO plan A is install sway and get an alignment...then ill go from there.

I also have a grinding or groaning noise that seems to be rear end related...might be axle berings maybe?

 

[jdpolzin]

How can this be a sway bar problem? Plenty of G-Bodies without sway bars out there.

Since you did some front end work I'd be looking there. Sounds like some serious bump-steer there if you ask me. How's the front end alignment and what specs did they use? What type of wheels and tires? How stock is the rebuild? Lots of questions before we can find a probable souce of the problem.

Acceleration wouldnt cause bump steer. Cornering causes bump steer. The front end isnt going to cause the car to twist under acceleration by just replacing front end parts or being out of alignment. Weak springs, swaybars, and swaybar endlinks in the front end are what causes twisting like that.

 

[turbofish38]

Anytime the car or should I say the front suspension moves up or down the spindles and steering arms move with it. When the Toe changes dramatically that is bump steer. It can happen hitting a dip in the road. Or a tar strip on the road. Get the darn thing aligned and eliminate that from the equation.


Stupid question? You didn't mention whether you have any adjustable control arms in the rear. If you do I'd remeasure the angle. Sometimes the difference of a degree or two between the uppers can cause the same condition. Make sure they aint binding either.

 

[HOTSIX]

The answer!!!

Okay lads....I finally got it to the shop and had it aligned. Shop said it was bang on. They then took a look at the SSM bars I have on there...rear boxed control arms.

They were not properly mounted and allowing the axle to move forward on the PS of the car under any acceleration. The shop was going to fix that however I decided after some thought to switch back to the stockers.

I cleaned them up and painted them. They go on tomorrow...plus my Hotchkis rear springs are making the car sit too low and I dont like it. They are coming out tomorrow and getting replaced with stockers too.

All said and done I did a good job with the front end of the car afterall!

Thanks for all the help.

 

[jdpolzin]

Good! I'm glad to hear that. I HATE SOUTHSIDE MACHINE BARS!!!!!!!!!!! Those things are the worst piles of crap ever made. If you decide to get rid of the Hotchkis springs, let me know, I'm interested. I do a lot of testing with different springs and the Hotchkis ones are the only ones I havent tried with a high HP car.

Also, if you have a welder or a buddy that has one, box those stock control arms in while they are out of the car and install new Moog Replacement bushings, those will help the car out a lot!

 

[HOTSIX]

Hey thanks!

I took the Hotchkis springs out - if you want them lemme know and we can figure something out. I can be emailed at justhoodman@gmail.com for quicker contact.

The stockers are back in (control arms) and stock springs too - the rear sway is back in too - car feels great - right where it ought to be.