THE INTERNATIONAL JAGUAR 'S'-TYPE REGISTER FORUM

Yes that's correct, only when the mounts are tight do up the stabiliser also if your car has them, the stabilisers under the front of the engine connected to the front suspension cross beam after the mounts

Apologies for tardy response, I’m having internet problems. Thanks for the suggestions. I’ll check the drive shaft orientation to start and may get it checked and balanced to ensure it is ok. Unfortunately I did not mark it up when I withdrew it for the engine out job. Am I correct in thinking that the motor stabiliser to the firewall should be done only when the motor and gearbox mounts are in position and tightened up ?

I would second the comment above about the engine and gearbox mounts. Many decades ago I removed the gearbox mount cradle (MOD car) and when replacing failed to get all the shim washers back in place as they came out. This resulted in a vibration at speeds around 50 MPH. Reshimmed the mount and eliminated the vibration so these are apparently critical.

Difficult to suggest anything without a lot more information but as Norman has said if the prop shaft has been removed I would start there. When removing a prop shaft I always mark the orientation between the shaft and the diff so it goes back the way it came out, same at the gearbox end.
Make sure the engine and gearbox have been put back in straight. Sounds strange but if the engine is not sat straight then your going to get strain on the prop shaft and gearbox mount.
Check the blades of the fan are straight and running true. Could have been bent during engine removal and fitting.
Are you sure it is related to you removing the engine and gearbox or perhaps the vibration was there before just being masked by the work that was needed on the engine.

I would suggest that you make sure that the drive shaft coupling flanges are perfectly mated, particularly the rear one coupling to the axle pinion.
You also need to pay attention to the engine / gearbox mounts.

When I purchased my car some clown had tightened the rear flanges so much out of position that the drive shaft flange was bent. No wonder he could not get rid of vibration!! When I was rebuilding R-R axles in a previous life for a hobby nearly every drive flange needed re-machining.

The same car had one roller of a "Timken" front wheel bearing that was "blue" and worn flat. As only one roller was affected it could have been hard to find. Obviously a warning to be sure from whom you buy critical parts as this roller was not genuine Timken. The vibration from that roller tended to increase during turns, but it was slight and would not have been all that obvious to an inexperienced driver.

Since motor and gearbox out, I now have a vibration in the car. It is not wheel related. Any ideas ?