I have a serious car vibration, only when the car warms up and I travel down the freeway at 110-120km for a about 15-20mins the vibration kicks in,i slow down to 40km still vibrates the car, after driving it for the next 15mins the vibration starts to go away. it feels like i have a flat tyre. I removed all tyres to check for wear. only slight wear in the inside of the tyre,tyres are just over 1 year old.(tyres are 235/35/18) i checked the tailshaft gearbox mounts engine mounts no problems.its my tyres or maybe its my diff? has any got any advise? or had the same problem before.it would be great to hear any comments.

have you lost a wheel weight? maybe get a balance and wheel alignment?

If you have a 6 speed conversion then your gbox ratio front to rear diff is out...and that causes the center diff to lock up due to the load and then you get huge vibration.

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Or even if you havent ... mismatched front and rear diff will do exactly what you're describing ... had your gearbox replaced?

I have my02 sti gear box and a rear LSD diff with 4.111 final drive..I have redline lightweight shockproof oil.(maybe it could be the Oil in the diffs) I will change the oil and see what happens.. Any ideas to what Oil i should try??

isn't the bugeye STi rear ratio supposed to be 3.9 not 4.11?

Its in a 2000 model.....with my02 gearbox..

yeah, the 6 speed STi box has a final drive of 3.9, and the rear diff should be 3.9

check this

The gearbox is a 5 speed not a 6 speed...

u did mention you have a MY02 STi gear box