1970 driveline vibration

[Scott #37632]

I have a '70 coupe with L-46 engine, M20 4speed and 3:36 rear axle. I recently had the engine rebuilt with new clutch, and rear axle gears replaced. The engine was internally balanced and revs smooth. However, on accelerating hard, when the revs go above 4,000 there is a moderate vibration in the car that seems like something is out of balance, causes the steering wheel to shake. The car runs and drives well otherwise. Any thoughts on this? Thank you

[John H.]

Re: 1970 driveline vibration

Could be a left side motor mount that's grounded-out internally (rubber deteriorated); you might also look at the trans mount and the rubber cushion isolation mount at the front of the differential mount bracket to the frame.