My 93 6spd lt1 car has a very bad vibration at hwy speeds. I feel the vibration whenever I put any amount of pressure on the gas pedal, doing about 2k rpms ineither 5th or 6th gear. I'm talking any amount of throttle at 2k and the car feels like the tranny or somethings about to drop. However if I drop it down into 3rd or 4th and romp on it there is no vibration and it gets up and goes. I have heard of many problem with the steel lt1 driveshafts and thats what I think this is any advice?

 

it could be the trans mount, how is it when shifting between gears, does it kick hard ? it could also be a bad motor mount

 

Ya it kicks a bit hard between shifts. I at first thought I was just a bit jerky at shifting but after driving my sisters Cobalt and my other sisters Cougar I came to find I can shift pretty smoothly and it's just the car. Right at the point where the clutch engages and disengages is when I feel the kick. Ialso wondered if it could be the u-joints? Something happened a few months back. I let my cousin drive it and he is kind of a noob at manual transmissions and when he went to downshift into 3rd he hit first and we were doing about 65mph on the hwy and let me tell you that thing practically stopped. Could this be the cause of whatever the problem?

 

well thats definately not a good thing! try having a local mechanic check out the trans mount first, then go from there

 

IF its in the over drive part of the tranny you need to get fixed ASAP. It may be repairable right now. If it comes loose it will most likely take out the whole counter gear and case turning a $500 repair into a replace 6 speed repair. They are going for $1500 around here.