86 XJ6 Rear Rumbling Noise
 

Hi - am new here but hope someone can help.

My 86 xj6 sovereign has been in a local independent jaguar
garage due to a breakdown (the cars' not mine!)

Whilst it was in there, I've asked them to have a look at
what I can only describe as a rotational type rumbling noise
from the rear of the car which seems fairly consistent at
any speed but is a bit more noticeable at lower speeds. The noise is definitely a rumble rather than a whining noise.

They've come back to me today with a list of faults
including rear exhaust boxes fouling the bodywork, rear
wheel bearing and they've advised that the diff has had it.

Obviously, this isn't great news, however for some reason
I'm not entirely sure the diff is the cause of the problem.
They've only carried out a road test but I was wondering if
the exhaust boxes fouling the bodywork / wheel bearing could
be the cause of the noise rather than the diff. I'd rather
find out if there were other possibilities before spending
fortunes on having the diff taken out and removed.

Any thoughts would be really appreciated. I'm probably wrong
but I thought the symptoms of a faulty diff was more a
whining noise rather than a rumble. Could this possibly be
down to a propshaft bearing? Or is there anything I can do
myself to either confirm or eliminate the diff here. I have let the car coast in neutral and it makes no difference to the noise at all.

If anyone else has had any similar diff issues, please let me know.

Thanks

Mmmm, you are NEW, so welcome aboard.

Your diagnosis is very good and quite concise, which makes a pleasant change, and also makes advice much easier.

Jaguar rumbling from the rear is nearly always rear outer wheel bearings.

Just for giggles, get a grease gun and grease the 4 nipples (zerks I think you call them ??) that are located on the 4 universal joints that make up the 2 half shafts. These are always forgotten, and many a strange noise has been cured with a few pumps of grease here. they can be tricky to get to, but patience will be your friend.

Tyres can cause a rumble, but not so common on Jags due to the weight and suspension design.

Diff output bearings can get noisy, and give a sort of rumble. The seals for those output bearings fail fairly regularly and that will, if left unattended, drain the diff of oil, and then the diff whine will be your best mate.

The exhaust is usually a thud and rattle noise, but I suppose if it has the correct angle of the dangle a rumble could be a good description.

The prop shaft centre bearing is also a rumbler, but generally becomes a screamer fairly quickly.

I would either decide to do some diagnosis yourself, with guidance from here, or find another Jag type place to give a second opinion, WITHOUT telling them what you already know.

These are simple cars really, and quite easy to keep up to spec, if you take the time to look twice, and repair once.