Upper Control Arm Bushings Bad

[Doug Hilliard]

I've got a vibration in the rear somewhere under hard acceleration at fairly low speeds where the load is highest and am trying to figure out what's going on. I've taken the rear suspension mostly apart and found my trailing arm bushings (BMR) on the chassis worn on the left side but not broken. I'm replacing those for good measure but don't think that's the source of the problem. Rick Crawford was helping me look at it last weekend and he could feel the upper control arm bushings were broken so I've removed those and confirmed the break (pics attached - front/back of the right side bushing but both are broken in similar fashion) though I'm not really convinced this is the problem either. Both sides have the rubber split so it's allowing the wheel to move forward more under load than stock would. I have ordered BMR's Delrin bushings for both sides which will hold the UCA much more rigidly. I'll post up results once I get it back together Thursday/Friday. Kyle at BMR has been most helpful as usual and got the parts out today! I should mention that the trailing arms were among the first suspension mods I did probably four years ago now so I am not surprised I have a little wear on those bushings as I have pushed a lot of horsepower for a long time on the car with drag racing and road course events. The BMR parts have been great! Stay tuned!

[Greg@PacePerformance]

Doug is the vibration only when the suspension squats?

I get a vibration when I have the trunk loaded and the kids in the back. I can hear it get slightly worse when driving and I hit a bump with the same load or if I accelerate with that load.

I'm thinking it might be my carrier bearing going bad or my Gforce CV's. Not sure just yet

[Doug Hilliard]

Doug is the vibration only when the suspension squats?

I get a vibration when I have the trunk loaded and the kids in the back. I can hear it get slightly worse when driving and I hit a bump with the same load or if I accelerate with that load.

I'm thinking it might be my carrier bearing going bad or my Gforce CV's. Not sure just yet

Greg, it's only under decently hard acceleration, so in that sense the suspension is loaded but with no extra weight in the car. How about educate me a little - what's the carrier bearing?
Thanks!
Doug

[BuildItYourSelf]

Look into what the diff is doing. If the bushings are worn the front could lift. Some people are getting it into there exhaust. (well there exhaust into it)
But it worth a place to look.
Only other thing I can think is the toe links and tire to fender.

[Doug Hilliard]

Look into what the diff is doing. If the bushings are worn the front could lift. Some people are getting it into there exhaust. (well there exhaust into it)
But it worth a place to look.
Only other thing I can think is the toe links and tire to fender.

Thanks! I have wondered about the diff. The toe links (rods) look good and I can't see any marks on the fender where the tire is hitting. It seems like a metal to metal. I've got the exhaust off the car so I could drop the rear cradle a little to get to the UCA bushings; I'll take a look on the pipes and see if there are any marks.

[Chewy]

The carrier bearing is the middle bearing for the drive shaft. Necessary due to the length and because it's a two piece shaft.

[Doug Hilliard]

The carrier bearing is the middle bearing for the drive shaft. Necessary due to the length and because it's a two piece shaft.

Ok, I figured that might be the same as the center support bearing but wasn't sure. I ordered a new one after mine broke but then found out my universal joint was bad. I picked up a salvage driveshaft and the universals and carrier bearing feels very smooth.

[TooManyHobbies]

Dang! Another thing to keep my eye on, but I do not beat mine as hard as you do yours

[Doug Hilliard]

Dang! Another thing to keep my eye on, but I do not beat mine as hard as you do yours

I hear you! I'm getting kind of tired of replacing stuff but I guess it goes with the territory!

[Doug Hilliard]

OK, I think I found the problem. I dropped the diff and there was a witness mark above the right side of the diff on the rear cradle above the diff. It looks like the bushings are just not strong enough to keep it from bumping up into the cradle under hard acceleration. I wish I had taken pictures but I was in a hurry to get it back together as the hours were ticking by and it was getting late, but my solution was to take some 5/16" inch diameter steel rod and cut 12 pieces 1.4 inches long. I drove those pieces into the voids in the bushings on both sides of the diff to take up that space and effectively stiffen the bushing. It was about a $5.50 solution. I also replaced the A-arm bushings with the pieces from BMR as well as the bushings on the trailing arms at the chassis interface. Problem solved; no more bumping and the rear just feels much more solid under the car. Thanks for the input gents!