Suspension Guru's - I need your help

[F00Mustang]

I've got a couple of suspension issues that I just can't seem to figure out. I really need some experienced help here.

1. When cruising - at any speed - the rear end will noticably jerk from left to right as I get on and off the gas. The track of the car doesn't change - it still goes strait, but the body seems to shift over the suspension. I dont think the wheels are moving around, just the body, and its only the rear end. I can feel my ass moving around and not my feet. I'm not talking about being off of the throttle in gear, and then the car lurches 'cause I floor it. I'm just talking about very casual acceleration on and off throttle (with the clutch allways engaged)

2. After being in reverse, say like pulling out of a parking spot or driveway, if I accelerate spiritedly, I hear a loud knocking comming from the rear of the car. This knocking will go away as soon as I shift to second gear or if I get off the throttle and then right back on still in first gear. I'm not talking about launching forward while the car is still moving in reverse, it will do it after comming to a complete stop and then going forward. If I really feather the throttle, it won't make the sound. The knocking is relative to engine speed, which leads me to belive it is the driveshaft hitting something, but I've looked underneath and can't find where it's hitting. I also don't feel it in the shifter - so I don't think that's it.

My mods are:
BMR LCA's - origional tubular design with bushings, non-adjustable
BMR ADJ. Pan-hard rod - with bushings
CHE Adj. UCA, again with bushings
Eibach Pro-kit springs and sway bars
BMR LCA relocation brackets with LCA's set to lowest mount point
4.10 gears (don't know if this makes a difference or not)
DSS 1 piece 3 1/2" driveshaft (steel 600hp model) - no loop (I know I should get one)
CHE K-Member brace w/ torque limiters
GMS motor mounts
Steeda Tri-Ax shifter


This is driving me nutz, so if anyone else has any input I'd appreciate it.

 

[SteveP]

one thing you may check is the diff seal. See if its leaking. If so, your bearings might be torn apart. (this happend to me. Had to replace the gears and bearings. This was because the guys who installed the gears didn't put it back together correctly.)

To me this seems like bad install.

 

[psfracer]

Well I think we can all agree that the knocking you hear when accelerating from a stop is not normal. Start with putting the car on the lift and see what is going on. Check the LCA bushings first. If one side was bad, perhaps that would create the feeling your talking about. Check the LCA's, and the UCA first. I know a long time ago some people where reporting problems with the BMR LCAs, as the bushings were cracking---BMR had since corrected the problem, but that was a while back, like more then a year ago I think.

 

[2kanchoo]

one thing you may check is the diff seal. See if its leaking. If so, your bearings might be torn apart. (this happend to me. Had to replace the gears and bearings. This was because the guys who installed the gears didn't put it back together correctly.)

To me this seems like bad install.

I second that. Also after you had those rear suspension parts installed did you get an alignment done? Might not be a bad idea. I'd want to make sure everything is aligned and nice and tight back there.

 

[thump_rrr]

Control arm suspension bushings are most likely split.
Pull the LCA's and UCA and check them.
If they are split get new ones and hand lube them with Energy Suspension Formula 5 Prelube.

 

[F00Mustang]

I do remember reading that somewhere. I have given them a look, but I havn't really had time to take them off and inspect them yet. If I'm lucky, that'll fix both problems.