5 replies to this topic

[rural mini]

Hi there could anybody tell me if all differentials are the same or any info at all

[rasputin22]

I believe all mini's were built with the same differential. This differential is a simple 2 pin geared diff.

There are a couple of alternatives to fit to the mini. A four pin diff works the same as a 2 pin bt has the added factor of being stronger and more reliable in higher tuned cars. These aren't overly expensive. An LSD ( Limited Slip Diff) is something mainly used in race cars, but people do put them in road cars and it makes the cars a little more fun to drive. Although these are quite expensive.

Another thing you can change attached to the differential is the final drive which consistis of 2 gears. By changing these gears you can make the car accelerate faster or have a better cruising ability. These do change from differing models and engine sizes.

Hope this helps somewhat, but the best thing is to get a tuning book for the mini which will be able to describe each option and more detail.

[Cooperman]

Basically, all diffs are of the same design, although the differentail ratios vary greatly. That is to say that the gearing between the two main components of the diff, the crownwheel and the pinion varies which, in turn, gives a different number of miles per hour per 1000 rpm in each gear.
The crownwheel and pinion come as a matched pair of parts and cannot and must not be mixed up.
To calculate the diff ratio, also known as the 'final drive ratio', you divide the number of teeth on the pinion into the number of teeth on the crownwheel. The highest production ratio was 2.7:1 as fitted to the very last Minis in 2000 and the lowest was 3.76 fitted to the original 850, original Mini Cooper 997 & 998 and Cooper 'S' 1071.
So, the lower the diff ratio number, the higher the final drive. Typically, a 2.7 diff will give around 22 mph per 1000 rpm in 4th gear, whereas a 3.76 in an 850, etc, will give 14.7 mph per 1000 rpm in 4th.
Lower diff ratios were offered for competition use and these include a 3.9, 4.1, 4.3 and 4.6, the idea being that you can then choose a diff rato which enables the car to pull its maximum possible revs in top gear during a competition and thus maximise the acceleration available.
To change a diff you need to remove the engine and gearbox. You can then remove the output 'pots' (in later cars, or the output couplings & shafts in earlier ones), remove end cover plates and the diff housing and withdraw the crownwheel assembly as a unit for service/repair. The pinion remains on the end of the gearbox mainshaft, but can be accessed if it is required to be removed to change the differential.
That is the main information. Of course, it can be a lot more detailed and if you intend changing the diff come back on here for a full description of how to do it.
I hope that answers your question.

[icklemini]

I prefer to term the 'final drive' as the crownwheel and pinion gears... this is then bolted to the 'differential' - the two things are different.

The differential is the same basic design, although there are a few subtle differencies/improvements made to it between 'a' and 'a+' boxes... Out of the two.. the A+ is the preferable...

[Dan]

Later differentials have a better design of thrust washer than earlier differentials so in theory should last longer but they tend to have lower quality pins fitted so end up being no better than the earlier type.

[Guess-Works.com]

As above, the A+ diff cage is the better of the two as it has two slots for a tang on the bronze thrusts to fit into, which stops them spinning with the pinion gear ( planet ).