Limited Slip Diff

[alawrence10360]

Trying to find a rebuilt 3.9:1 is like trying to find a unicorn
Is swapping to an LSD a viable option ?

[les]

I’d view it as a bit over the top, for a road going Minor.

[philthehill]

Unless you can find a ready built LSD diff assy you will still have to build up the crown wheel and pinion as the crown wheel LSD carrier will not have the same tolerances/pre-load as now.

[alawrence10360]

This what i was thinking of
It says its a direct replacement of the diff

https://rover.ebay.com/rover/0/0/0?mpre ... 3551855094

[philthehill]

Thank you for posting the link.

The LSD shown in the link requires the diff assy to be totally re-built and the meshing of the crown wheel and pinion to be adjusted to suit..

The LSD shown is the mount for the crown wheel and has to be adjusted sideways in the carrier to correctly mesh with the pinion. The pinion will also require adjustment fore and aft in the carrier to correctly mesh with the crown wheel.

Unless you have the experience, special tools and the required parts for the build I would not attempt it.

Phil

[alawrence10360]

I think your right
I initially thought you remove the diff and fitted the LSD

[Declan_Burns]

A.Lawrence,
I have just caught that unicorn!
There is an apparently good 3.9 diff for sale not too far from me.
399€ o.n.o. If you are interested and cover the postage costs I could get it for you. I don't know what a diff weighs but I would hazard a guess at 10kg. Postage to UK from Germany up to 10kg~21€, Postage up to 20kg ~32€.The inter German postage cost would be approx. 9€<10kg … 17€<20kg. Maybe he would send it to you directly. I do not know the guy so it would be all at your own risk. Feel free to contact him.
Here's the link.
https://www.ebay-kleinanzeigen.de/s-anz ... 8-223-1940


Regards
Declan

[IslipMinor]

A very regular contributor to this Messageboard, now sadly departed (BMC Ecosse), would have had a field day with all this talk about 'diff ratio'! He would often point out that the actual 'differential' has a ratio that can vary infinitely between 1:1 and 2:1, and that is between the rear wheels on each side of the axle, and nothing to do with the rear axle ratio, so there can be confusion about what you get when buying a 3.9 'diff'?

Even the BMC Parts Manual refers to the combination of crownwheel & pinion + differential as the 'Differential Assembly', so maybe an awareness of what to expect when looking for a 'diff' is all that is required?

As has been found out, the website selling the LSD are only selling the differential part of the rear axle assembly, to be fitted into an existing carrier, and more than likely using the existing crownwheel and pinion. Followed by, as Phil explained, a set-up process that requires knowledge, special tools and equipment to do.

With regards to LSD there are 2 basic types - 'Torque Biasing' (Quaife are the best known) and 'Plate' (originally Salisbury, then Tran-X and now also Quaife, who bought Tran-X).

In a car like a Minor with simple leaf type rear suspension, the loss of traction is often caused by a rear wheel not being in contact with the ground very well, and virtually spinning freely (axle tramp when taking off smartly at a 'T' junction, whilst turning right is a common occasion). In this instance the torque biasing LSD does not work well, as both tyres need to have some grip for it to work. The plate type LSD 'pre-load' ensures that some power is transmitted to the laden wheel when the other wheel is on a very low-grip surface, or even in the air! The amount transmitted depends on how the LSD is set up.

[alawrence10360]

A.Lawrence,
I have just caught that unicorn!
There is an apparently good 3.9 diff for sale not too far from me.
399€ o.n.o. If you are interested and cover the postage costs I could get it for you. I don't know what a diff weighs but I would hazard a guess at 10kg. Postage to UK from Germany up to 10kg~21€, Postage up to 20kg ~32€.The inter German postage cost would be approx. 9€<10kg … 17€<20kg. Maybe he would send it to you directly. I do not know the guy so it would be all at your own risk. Feel free to contact him.
Here's the link.
https://www.ebay-kleinanzeigen.de/s-anz ... 8-223-1940
many thanks but i have already ordered one unfortunately..


Regards
Declan

[Monty-4]

Healthrow Transmissions will do you any ratio diff you like as a plated LSD or with the ATB variant. At the risk of stirring up the hornets nest I would suggest the ATB would be more suited to a Minor road car.

Both options are not inexpensive, of course!