Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Graunching grating grinding

Just got back from touring the Spanish Pyrenees (they've got this red stuff you are supposed to drink - Rioja or something like that - it was hard but somebody had to do it). It was very hot - 38-39ºC and lots of tight hairpins. When the car and transmission was really hot I got this rubbing grating noise from the back of the car when going around tight corners (there were a lot) either left or right turn. It has steadily got louder. There is nothing obvious to see inspecting the back axle, U bolts, Panhard rod or anti-tramp bars etc. No slack in the wheel bearings. Nothing loose.

Only happens when the car is very hot. Something wrong with the differential perhaps. Have you knowledgable TMers any suggestions?

Felix,
it might be you need to change the diff oil. I have some if you want it as I bought it to do myself at I think 35k & Allon White did it at the service at less than that mileage.
We had that noise occasionally. Now it is completely gone.
John

Felix42, it's deffo the Diff, my S1 always did it in France due to the heat.

Change the oil for a good quality 80-140 with LS grade (limited slip) I also used to add a squirt of Friction Modifier & all was good for the next 10k miles or so

If your interested in the tech reason...
Your Roadster has a BTR Australian Axle
It uses cone disks for LS and strong springs set the static pre-load
As the oils break down / thin, eventually could lead to wheel locking under slow corner (hence the graunch or clicking)

Thank you Jon and John - very helpful.

Does anybody know the capacity of the differential?

Thanks

It's the LSD which makes that noise. I've only heard it when reversing slowly up the drive and it sounded like a loose wheel...….

You'll need a couple of litres, maybe a bit less. even when the additive is already in there I've had to throw a bit more in - available from Demon Tweeks and similar.

Very unscientific, I just add like a spirit shot.

Thanks Dave.

Castrol Syntrax Limited Slip 75W-140 Axle Fluid for LSD 

This is the stuff for a BTR axle.

My 1999 Plus 8 with BTR is 1 Litre, I would be surprised if yours is any different.

I use MPD Motor Parts Direct and their LS80W901L Part number it was £4-99 a litre last time. I'm pretty sure it was a Comma product, the local Rally boys use it in their Scoobydoos I've used this for 15 years without any modifiers and never heard a tweet out of the rear end.

Now £7-55 LSD Comma

So it's not just M3W's then