www.jec.org.uk

Hi,

My low mileage and otherwise serene 1971 4.2 litre XJ6 series 1 has developed a whine from the rear that I believe is due to the diff. It occurs when I take my foot off the 'gas' between 50 and 60 mph and disappears as soon as I touch the accelerator. It is not heard at other speeds when the engine switches from driving the car to retarding it.

I have tried replacing the diff oil with new EP 90, augmenting this with additives that are supposed to quieten matters and even fresh (unaugmented) EP140 to no avail.

I'd be grateful for any suggestions including recommendations for companies who rebuild diffs or offer refurbished units.

Many thanks in advance,
Dave.

I don’t have any personal experience of dealing with them but I believe that Simply Performance are well respected.

https://simplyperformance.com/rebuild-service/

AJS Engineering is a well known name in Jaguar circles for rebuilding differentials. Dana also offers a rebuild service, if you do decide to bite the bullet. Mike.

It might just be worth checking the rear engine mount. If deteriorated (and they do get soaked in oil) under deceleration it could let some part of the drivetrain touch the mount or chassis and transmit whine.

Many thanks for your help gents - I'll investigate further and report back when the issue is resolved. (I did replace the rear engine mount last winter as the rubber was in a very bad way - no change in whine characteristics unfortunately.)

Dave.

Just to complete the story, with the help of friend we did dismantle the IRS, and I took the diff to AJS Engineering for a rebuild. With everything reassembled I'm very please to report that whining issue is resolved. I highly recommend AJS Engineering!

Dave Edwards

That is good to hear. I have the same issue on my XJ Series 1 which one day I expect will need to be done. It's been whining for over 30 years now but it would be nice to have the cradle out and sort it.
Dave