whys the diff so weak?
Turbo Mini Forums

ok after readin what turbo dave wrote in the wanted bit, howcomes the diff doesent like goign round corners at ful throttle? i was unaware of this and always told to take it steady at launch never round corner, is it just becouse then all the torque is then put through ONE of the plannet gears and so it cant cope? or am i way off?
and how much do second hand 4 pins come up forsale and how often? i will check ebay in a sec tho.

cheers! Dan

May be as the mini was designed with not much power and skinny wheels ???

Metro turbo weekend driver,Mini turbo in the making again!

lol, i can understand that it is now 40/50 year old design and so is not bullet proof like most of todays box's, but just wanted to make a bit of an understanding of why, is it poor meterials, poor desighn or something.
i am guessing the desighn is fine for standard 1275 etc, but when you bring more like 90s power then the 4 pin is a much more usable diff.

oh well lol

Dan

generally its down to tollerances!

I've seen a std gear box fail in 60 miles!!!! It was a std mpi mini.

Rover can't build anything well!

Alex

AlexF

Diff was designed before 1959, to deal with a hefty 34(?) bhp from an 848cc engine.......

Needless to say putting more than three times that (in some cases) means it is operating well beyond its original "design envelope".

Guess Austin's safety margin didnt stretch that far! Still it does well to cope with 2 to 3 times that output fairly easily. shows in the old days they built them to last (within reason!)

the diff has been re designed over the years

alex

AlexF

It has? What changed with the std item then? Wasn't aware they were any different over the years?

different pins...

there was a lump in the middle (I cant think of the term for it!) and the cage changed slightly

not much I know!

by actually lining up the bores in the cage you can make a std diff work with high powers!

AlexF

The bronze washers did get a tang on th em some time. That really increased the life of the diff. Alsi material spec changed in the pin.

Remember guys, ALL cars are built as cheap and simple as will suffice. Apart from RR of course! This means that the standard diff, with a mechaincal minded driver will last for ages.

Last diff that I rebuilt had new Rover planet gears. On one of the gears the bore was only partially machined, the core had too big a bore that did not clean with subsequent machining. Teeth had not been de-burred after machining so there were metal chips on the outer diameter. In short lousy workmanship !

Seeing those made the old wisdom crystal clear: with ANY build, be it engine, gearbox or whatever, it is the little details that count. Cleanliness, tolerances, surface finish etc. In most cases that is also time consuming since it is manual labour that costs. Simple as that.

took my diff off the other day, and i now understand why corners and wheelspins damage the diff unlike any hard acceleraiton while both wheels are tunring the same amount
understand first hand better than anyone ocul have explained, theres a bit of play in my pinion wheels but not much, still owrth the 4 pin...if it ever arives!

cheers, Dan