I've noticed a few times I'm getting a loud sharp thud/thump coming from under the car when punching the gas hard, mainly in S mode. Just this morning it happened and it felt like the thump reverberated through the entire car. It doesn't do it all the time either. I have just recently replaced both engine mounts as they had ruptured and leaked fluid out of them. My cat has 82k miles. Could this possibly be the transmission mount checking out??

Could this possibly be the transmission mount checking out??

Yes also I think it could be the prop shaft.

Possibly Jurid (rubber ) coupling or prop shaft bearing.

Search this forum for info (I use Google for forum search).

My bet would be on the trans mount. Just replaced mine at 105k miles. It should have likely been done at 60k miles when both engine mounts failed. Probably the best single thing I've ever done on my car to improve driveability. If your engine mounts failed, then most likely the trans mount is with them.

The back end of my trans had to be raised over 1 inch to line up with the fresh mount. Talk about a difference in NVH!

Curious Mr Hamilton, what symptoms, pre-new mounts, was your jag exhibiting?

I occasionally used to have a thud on my earlier X350, it was accompanied by a bit of a lurch sometimes, after having the gearbox " re-flashed" it never happened again, I did a further 90000 miles and no repitition, took the car over 200000 miles before trading it for the Super V8

General drivetrain vibration, droning on the highway, clunky shifts. All gone now.