Hi Guys,
I have a stype Jag 2002 3.0 petrol.
have owned her now for 21 years, 10 years ago it started to make a grunt noise it grunts then stops then grunts with a 2 second gap it happens at speed 48-50 mph only, and when I take my foot off accelerator it stops and resumes when foot goes back on then it disappears, I have taken to numerous garages and left them scratching there heads, been waiting all these years for something to break but it’s still happens , any ideas please.

 

Something from the transmission? That would be my first guess. It can be very tricky to isolate the source of noises.

Try switching the transmission from normal to sport mode, or visa versa. This changes the shift schedule a little bit. See if the behavior changes.

 

Based on your description, the noise could be an incorrectly set or worn pinion gear in the differential.

It could also be something caused by the gearbox (sorry, transmission here in the Colonies) as Karl noted.

Did the garage check the fluid levels of the gearbox and differential whilst performing any diagnosis?

 

Also, in the spirit of Christmas, I ask that it be duly noted that I refrained from making a cheap joke even with the glorious setup of "Grunting Noise from Rear" as the thread title.

 

Ok, I'll do it, in the spirit of Christmas.
Mother in law still strapped in the back?