Gearbox question

[aimlessrock]

Folks, I have fitted a 3.91 diff to my 320i cabby to give it some longer legs when cruising but the result is that first gear is now almost useless.

I have a factory 240 box fitted and was wondering if a 260 box would make any difference, as I note it has lower ratios.

any input would be welcome- if anyone has a good one for sale/swop please pm me.

Thanks Gary

[BenHar]

What was the ratio of the previous diff?

What do you mean by "longer legs"? To me it means lower revs for the same speed. Which would mean first is a higher gear and more useful.

Ben

[jmc330i]

I've got a 240 box with a 3.91 and first gear is fine.

[aimlessrock]

previous was a 4.10 (before that a 4.27) and both are just a bit to revvy. - longer legs= lower revs when cruising.

James- are you running a B20 also?

Mine is a cabby and with the factory hard top on she is quite heavy- would this make a difference?

[BenHar]

previous was a 4.10 (before that a 4.27) and both are just a bit to revvy. - longer legs= lower revs when cruising.

Going from a 4.1 to a 3.91 will have made first gear higher. What do you mean by "the result is that first gear is now almost useless"?

Do you mean you can't pull away because it is too high?

Ben

[aimlessrock]

Hi Ben,

First gear is now very high.

the car can pull away in 1st, but to get her moving from a standing start your need lots of revs and then have to instantly change to 2nd.

[BenHar]

If you are having to use lots of revs then it seems that first gear is too high. Not sure why you have to change to second instantly.

According to http://www.e30zone.net/e30zonewiki/inde ... in#Gearbox the 260 has a higher First gear than the 240 so I don't see how it will help.

Ben

[Brianmoooore]

Simple fact is that 3.91 seems to be too low for a short stroke engine like the B20. 260 box would make the problem worse.
The only effective way of getting what you want is a longer stroke engine, such as a B25, to get some low down torque, or a six speed gearbox.

[aimlessrock]

Simple fact is that 3.91 seems to be too low for a short stroke engine like the B20. 260 box would make the problem worse.
The only effective way of getting what you want is a longer stroke engine, such as a B25, to get some low down torque, or a six speed gearbox.

thank Brian, I had not considered a 6 speed box...this could be the best option. anyone had any experience of this?