Talk Morgan Forums Morgan Sports Cars Classic Morgans (pre-CX) 3.7 differential

Folks -a friend has a 3.7 roadster which has an issue with its diff. Can the forum advise which diff is fitted to a 3.7 and, even better, can someone suggest where spare parts for the internals can be got.

Cheers!

Robbie, very unusual for the later BTR diffs to fail, what's his issue ?

BTR M76 LSD axle 3.077:1 ratio.

GoMog has some info here and a 3.08:1 ratio mentioned (rounded up from actual). If the issue concerns the LSD it seems Quaife offer an upgrade at a price.

Jon,
A noticeable “clunk” on engaging gear and a rattle like noise from time to time - the diff was dismantled and,apparently numerous bits of metal were evident.

Robbie

As above I not heard of a BTR diff failing except in competition cars.

Has it been run dry of oil by any chance?

The Quaife upgrade (from Richard's link) is a well respected upgrade as it gives a much more "progressive" take up of the drive to both wheels. If the diff does indeed need replacing then go for this every time.

The best person to talk about Morgan diffs across the whole range is Billy Bellinger at JB Sports Engineering https://jb-engineering.co.uk
He deals with everything from Series 1s , through Sailsbury axles to BTRs. A true enthusiast (and a vey good racing driver) who I can recommend 100%

It may be too late already but if not, try adding some friction modifier. BTR LSD's tend to chatter and snatch at low speeds but quieten down once moving.

I had that issue on mine particularly when manoevering on full lock when LSD cone clutches would click. Redline 75W90 full synthetic LSD oil solved it.

Just resurrecting this subject.

I have a 3.7 Roadster and am getting clunking from the diff. When de-accelerating and then accelerating (backlash), and also sometimes from stationary (as though the brakes are stuck on and then releasing, but it isn't the brakes as the wheel cylinders were replaced at a recent service). The diff oil has been changed twice recently, but hasn't improved the situation.

My wife has even noticed and commented about the clunk when changing gear, so it must be noticable! To me it sounds like a drivetrain issue, but as the car is a 2018 model with only 13000 miles on the clock I don't think it's UJs. I have checked all the suspension fixings, checked the wheel splines (wire wheels) and all seem OK, but have noticed the play between propshaft and rear wheels seems a little excessive - I've measured 5mm rotation on the outide of the tyre tread before the prop shaft rotates, does that seem excessive?

I will talk with Techniques and JB Sports for guidance, but any pointers from our esteemed experts on here?

There is noticeable backlash between propshaft and wheels Les which I believe is down to crown wheel and pinion clearances so normal. When reversing slowly I can often hear this backlash especially with lock on but put this down shaky clutch foot.

Have you tried greasing propshaft UJ's? The rear one by diff is easy but forward ones require some ingenuity to get a grease gun in. I believe John V6 had to make an access hole in rear of transmission tunnel to gain access as no possibility working underneath on his Roadster.

You say you have changed diff oil several times but with what? You must use oil with LSD friction modifier included or add it to existing.

Yes I did Richard. The post in on here somewhere. I can't find my write up but can post pictures.