loose? rear suspension

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Fireofficer5

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Sep 23, 2023
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Location
Davie, Florida
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95-96 Cougars, 323 and 281
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Like the title says, upon hard launches, while looking in the drivers side mirror, the left slick seems to move forward slightly.

I have replaced all the rubber bushings in the upper and lower control arms.

It is able to be felt near the finish line during a bracket race like a pull to the right during on and off throttle work.

the car, before has been said to crab during a race.

Thats all the info I got right now.

Is this a rear suspension mount bolt or bushing issue?

Any one have experience with this problem?

Thanks Rick
 
Everyone has that problem, pretty much.Replacing the irs bushings with the delrin ones, adding a diff brace or two, and replacing the toe limiters is fairly effective.There's bracing for the rear of the diff, front of the diff, and subframe connectors to tie the irs into the unibody. Once you get that, it'll be wheel hop next, lol.

edit: If it's actually crabbing off the line, your irs bushings are probably wasted. That's the only thing bad that will let it move that far; That's usually when a straight axle car slips the spring connection, and slides forward on the leaf spring. We should not have anything that moves that far.
 
The subframe connectors hold the front of the IRS pretty solid. But they're heavy. They bolt to the front mount, and get welded in.
 
Delrin LCA bushings correct that. Sally Hodges shot some great shots of my rear tires at the Shootout one year where it was clear that the wheels were moving forward significantly in the wheel wells on launch. I swapped out the rubber bushings for Delrin right after that.
 
I got the UHMW bushing from SCP. They are hard plastic of some kind.

The toe link as well.

Does the whole rear subframe move and cause this?
 
Yes; those bushings are supposed to keep it from moving. The irs bushings and the knuckles and control arm bushings are the only play in the system. Mount an iphone under the car so you can see what's moving. or, you can get a cheap 1080p camera on amazon for $20. It's only going to move when you're power on, sot hat's really the only way to find what's moving.
 
Looks good! nothing wrong with those, imho.
 
Fireofficer5 said:
I got the UHMW bushing from SCP. They are hard plastic of some kind.

The toe link as well.

Does the whole rear subframe move and cause this?
Click to expand...
They are polyethylene. The UHMW stand for Ultra-High Molecular Weight. Very slippery stuff. When I last bought bushings from SCP (2003 or so) they were making them out of polyurethane. I wonder why they changed. Polyurethane was very stiff. I used to work in manufacturing and I've never used UHMW in a compressive application. It generally used as a slippery wear surface.
 
He still sells the polys along with the uhmw. The uhmw is harder, I think in between poly and delrin. I've got the uhmws in my lcas and spindles.
 
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