Is this motor rocking enough that the mounts look good? They aren’t torn, but are a bit cracked. I just replaced both of the vibration dampers. I’m trying to track down the source of a vibration that comes on around 4K rpm and continues up to redline. Almost like a growl (full engine growl for lack of better explaination), it can also be felt in my feet by the firewall while reving the car. Car has lots of power and runs smooth up to this point. It also has lots of power through this vibration up to redline, but it obviously causes me to back off and keep the revs under 4K. The vib is there in neutral parked in the driveway or in gear and clutch pedal up or down makes no difference on vibration.

I’ve recently refreshed the clutch pack and it was balanced at a machine shop with new throwout and pilot bearings installed, so I think I can eliminate that.

New torque tube bearings from Black Sea, but because the vibration is still there when the clutch is disengaged does that isolate it to the engine?

I’ve also replaced plugs, wires, cap, rotor, coil, fuel injectors in case it was caused by a misfire, no luck

Originally, I was hoping this vibration was part of the pilot, throwout or torque tube bearings failing because they were making noise, so it’s been there the whole time, but was just lurking behind those bearing noises. Changing those hasn’t helped with this vibration

Any ideas?

They look ok to my untrained eye, ie. not torn or severely cracked, but I think I’m going to replace them and the motor mounts just to be sure. Just have to get them ordered from Roger. Thanks for the reply Stan

Does this mean the engine rock method for testing the MM doesn’t work for the none hydraulic mounts?

Thanks buddy. Trans mounts on order.

Anybody know where this trans vibration damper (12) is located? I’ve been under the car and dropped the trans a bit when I did the torque tube, but haven’t seen it.

Thanks Sean. I’ve read your thread about your experience changing out yours and it had me thinking maybe mine... Good thing is for the ‘78 the damper is only $150 from Porsche, so I may just grab one and slap it in. Worth a shot

Thanks guys, I’m with you about replacing old rubber. Damper and motor mounts ordered. I’ll keep you posted.

Hey Brian,
Good to hear from ya. Parts should be a few weeks. Sounds like I may get the motor mounts in first, although I wanted to do the balancer first, so we’ll see. When I do do the balancer I’m gonna change the water pump, rebuild the tensioner, front crank seal, oil pump seals and cam seals, and the timing belt. I’ll definitely do the balancer and mount motors one at time. The car is coming along, thanks. I just got my a/c blowing ice cold and other than this vibration the car is running and driving great. Once I get this figured out it will be on to the exterior, paint, weatherstripping and finish off the interior, but that may next year. We should get together sometime. I’d love to get a second set of eyes and ears on this vibration. Take care buddy