Ok, so I just finished installing my suspension on my 85 Camaro Z28. Eibach Sportline springs front and rear, KYB AGX shocks front and rear (set to the stiffest setting) UPI sway bars front and rear, BMR rear lower control arms, BMR rear lower control arm re-location/2 position brackets (set in the lowest hole) BMR adjustable Torque Arm, BMR Front Steering Brace (AKA "The Wonder Bar"). On the way home from the shop, Every decent sized bump I hit in the road it sounded like someone was hitting the back end of the car with a sledge hammer. It was a very loud "Bham" coming from the rear. So my question is, have any of you run into this issue before? Do you think it's bottoming out? Do you think the bump stops need to be shaved? Do you think it's the rear shocks being set to stiff? Any and all help with this will be greatly appreciated.

Thanks Tom

 

Its the Torque arm bracket on the differential hitting the underneath of the chassis under the rear seat area. Its normal. It will "Clearence itself" in no time. THey all do this when the cars are lowered enough. If you try and hammer the area and bend it, it will look worse. The undercarraige sheet metal will stretch in the area it hits and like stated it will clearence itself nicely and as clean as you need. My car was extremely low and it did just slightly puncture the sheet metal but was still no big deal.

I attached a picture showing where it hits underneath. I circled the area but it is actually on the other side where I point the arrow to. I just circles this side showing refenece to where it hits on the other side- I have no pic of the other side.

 

i agree with dean, its most likely the rear hitting the floor. Jack up the rear of the car and take a look int he tunnel buy the torque arm mount, should be pretty obvious where its hitting. And as Dean mentioned, it will "clearance" itself.

However, i dont know how low you car is sitting, but my car with sportlines, and a aftermarket torque arm never had any issues hitting the floor with the stock rear. I did/do have issues after i swapped a moser 9" rear though, the torque arm rubs the side of the tunnel a little and the upper torque arm mount on the axle itself hits the floor behind the rear seat.

 

I agree with the above. I rounded off the corner of my Spohn torque arm and have not had an issue with it hitting the floor pan, even with shaved bump stops. I am reasonably low. Have you centered the rear yet with you panhard bar?

 

I drove the car back to the shop yesterday and put it up on the drive on rack. Once it was in the air, we started jouncing the cars suspension up and down. "Bingo!" Found the culprit. The upper panhard bar bolt was not completely tight. As the suspension flexed the bar would shift and pop on the threads of the bolt. Tighten it up and the noise went away. Took the car for a spin around the block, yup that solved it!! Oh, and yes the rear is centered with the adjustable panhard bar. I need to take the car out on to some back country roads this weekend to see how she handles, so I can make any adjustments that are needed.

 

I'm glad it was an easy fix.

Next time you're under the car be sure to check out the clearance for the front and rear bump stops. I am slightly lower than you and only had 1/2" travel on the rears. Once I cut down the rear bump stops the ride quality increased significantly.

 

Thanks for the info guys/gals, I'll be sure to check my torque arm clearence as well as the bump stops. So far so good though, Im really happy with the mods I've done. Wouldn't have done the mods right if I had not joined this forum. Thanks to all of your knowledge on these bad *** 3rd gens.........