[Cobra0331]

sup yall, new guy here..i have a 99 cobra, i recently bought 4 new tires (hankook ventus) 275/35/18's in the front and 285/35/18's in the rears..i got them mounted and balanced.after that i got an alignment done as well..the car is lowered, therefore i have not installed new caster camber plates, i will soon..but at around 60mph and 80 mph my car shakes..i do need new rotors as well..im just not sure what the problem could be..thanks...

[First5.0]

miss-balanced tires could cause it.

[Cobra0331]

like i mentioned, i just installed those new tires and i got them balanced, unless they did a crappy job? i would hate to go up there again and tell them how poor of a job they did, and them tell me its something else..lol

[First5.0]

I had mine balanced at one place, got steering wheel shake at 55 and 70, brought it to another shop, they re-balanced and now its as smooth as ice. Is it full body shake or steering wheel? More of vibration or rattle?

[Cobra0331]

the steering wheel doesnt shake much..and it feels like its full body..and alot of vibration..the passanger seat looks like it could be one of them vibrator massage seats u see at the mall..haha..but no rattle..thats why im all sorts of confused...

[ITLRUN]

It could be your driveshaft out of balance shaking like that. Or I've seen this happen a time or two, check your tranny where it bolts to the back of the block. If you have a few bolts come loose, they'll cause a shake you wouldn't believe, Mike. SCT Tuner.

[Cobra0331]

wow, sweet deal, never thought of that..i might have to check that out..i appreciate the help!

[TrueBlueNewEdge]

It might be your drive line is out of phase. Very likley if the car is lowered. If the vibration is worse under heavy acceleration and gets better when coasting at the same relative speed it is probably your differential pinion is nosed up too far. Under acceleration the diff case will shift nose up causing your driveline to go out of phase. Check this link:Driveline Alignment. My Cobra was is lowered 2" and driveline was way out of whack. Following that link as a guide line I was able to smooth out vibes I was getting at 80 plus mph. I haven't figured out how to shim my diff though. Anyone have any ideas on that?

[04CobraBlade]

while you have your driveshaft out make sure your pinion nut is torqued (dont know the exact torque but it will be over 200ft lbs). and to TrueBlueNewEdge 8.8 diff from factory has a crush sleeve but 5.0 resto has the shim replacement.

[TrueBlueNewEdge]

Hey 04 I meant how to shim the diff case to alter the pinion nose angle? On a straight axle you would adjust the LCAs to change this angle. Does that make sense? I don't know how you would adjust on an IRS setup. I would imagine you shim the mounting points somewhere?