Well did a 5-spd swap on my 1997 sc300 this weekend took it down the street and it seems like 2nd 3rd and maybe 4th gear have a vibration in the driveline between 2500-5k rpm. second gear seems to be the worst espically half throttle or better. 5th gear on the highway seems fine no matter the rpms or throttle precentage.

Im not sure what the culprit is weather its the driveshaft, carier bearing the rubber insulator between driveshaft and rearend or possibly something else? help please

 

How's ur tranny > dif alignment? If off by a degree it could cause these symptoms.

 

there's only one way the big rubber thing goes on the diff and tranny. if that's not on the right way you'll get vibrations.