diff and gearbox advice

Tue Nov 13, 2012 6:56 am

Hello,

I am after some advice on diffs and gearboxes.

I am the owner of the Silver C2 Alpina that recently had a new roof skin and respray, (which I put up a thread about) I am now working on bring the running gear back up to how BWM intended it to be. When the Car was built it was an Automatic and Alpina put a 4.1 LSD on it. Since then someone has put a manual gearbox on it and just a standard 3.91.

I am going to keep it Manual as I am not overly keep in auto's but I am not sure what to do about the diff. (the one that is on there at them moment is making all the normal noise of a + 150k miler)
I like the idea of finding 4.1 from some where (from where I have no idea) or making up a 4.1 LSD as that is what come with the car when it was built and this is the bit I know nothing about....

If I was get one and put it on the car, is it going to become a little undrive-able? 0-60 is going to be epic, but what about when I am not racing Boxters off the lights?
Does anyone know if BMW put a 4.1 on a manual or was it a Auto box only thing because of the gearing?

I suppose the question I am asking in the Zone"s opinion what should I be putting on to the car...

Normal or sports 325 gearbox with 4.1 LSD diff?
Sports 325 gearbox with 3.91 LSD diff?

thank you for your help...

Tue Nov 13, 2012 7:34 am

for what its worth there isnt a dramatic difference between using a 3.9 and 4.1 diff, it will feel livelier on the 4.1, but the 3.9 is a nicer ratio for every day driving, as each gear will have a wider range of mph that it will cover.

even with 275bhp from my s14 in a race car over a lap theres very little performance difference to be had. if you want a 4.1 lsd automac often have them.

Tue Nov 13, 2012 1:27 pm

Many thanks. Sound like 4.1 then. Who are plug? do they have a web site?

Tue Nov 13, 2012 4:16 pm

Search for a few diffs on Ebay and you'll find the company he means. Doesn't mention what has been done to warrant the high prices though.
I'm rebuilding mine at the moment, will hopefully have the information added to the Wiki when it's done. Total cost comes to about £350 just for parts, or if you're not confident speak to 'gareth' on here - he's our resident diff guru

Tue Nov 13, 2012 5:32 pm

i agree, the prices for the company i meant seem a little high, but i bought one off them earlier this year when i needed one in a hurry, and to be fair to them it was described as being new/perfect, although had been used, well i stripped it because i wanted to increase the number of plates in it, and i have to say it was in perfect condition internally, i even reused the fricton plates it was that good, when i see what some people ask for ropey unknown condition lsd's i think the price they asked was reasonable, although i will say they seem to want a lot of money for a loose cwp