I bought another XJR (my 2nd).

The exterior was excellent. But there were a lot of issue mechanically. All of the suspension has been replaced. Engine mount has been changed.

But there is a problem that me and my mechanic can't ping point.

The engine idles very smooth and quiet. In reverse is also very quiet. But when I put car in drive. Engine is quiet loud and you can hear it growl.

I am not sure what is causing this. The engine with no forward gear load, is buttery smooth and quiet. Just in forward gear its loud. In neutral, reverse its quiet.

Transmission was serviced and problem is still there. It shift fine and smooth. Just engine noise.

Despite the noise does the car drive normally ?

Yes it drives normally.

The only thing that is weird is that sometime the AC compressor won't engage.