E30 Zone

I've got the m52 in with the getrag260 box and have been offered a 3.25 LSD diff I've got an LSD in at the min but there's no tag and I think it's a 4.10 what would be best and what benefits will I get from each as I'm a bit lost when it comes to ratios

4.10 is a lower gear ratio than a 3.25, so it will give you better acceleration but rather busy on the motorway.

http://www.e30zone.net/e30zonewiki/inde ... fferential

The 325i usually had a 3.64:1 while the Sports had a lower 3.91:1 (but also a close-ratio gearbox).

So, it very much depends on what sort of motoring you mostly do...

Verry rarely do any motorway miles just country lane blasts

3.25 is a bit of an 'odd' ratio for E30 use. It's to high to use with an overdrive fifth gearbox (it will blunt the acceleration) but it's a bit on the low side to use with a direct fifth gearbox, especially with the power and torque from a M52.

Brian could you explain what overdrive and direct drive 5 th gear mesns...its always baffled me

You would need an E36 box to make use of the diff

Just found out mine is a 3.91lsd so I'll stick with that

macas wrote:Brian could you explain what overdrive and direct drive 5 th gear mesns...its always baffled me

It's to do with the way the boxes evolved. The box fitted to the E30 was originally designed as a four speed box, with top (fourth) gear being a 1:1 ratio, with the input shaft locked to the output shaft, and the layshaft rotating, doing nothing.
When the evolution of the motor car demanded a five speed box, an extra gear on each shaft was housed in an extension grafted onto the rear of the box, with ratios such that the output shaft rotates faster than the input shaft, rather than slower as with 'normal' gears.
When the E34 and E36 were introduced, they came with a gearbox that was designed as a five speed unit from the start, with top gear (now fifth gear) rotating the output shaft at the same speed as the input.
Then came the six speed box, and the same thing repeated itself - a bit grafted onto the back of the five speed box, containing 'overdrive' gears.

macas wrote:Brian could you explain what overdrive and direct drive 5 th gear mesns...its always baffled me

This illustrates the workings of a 4-speed gearbox, where 4th is a direct 1:1 ratio;

http://i0.wp.com/blog.prosig.com/wp-con ... =400%2C330