M42club.com - Home of the BMW E30/E36 318i/iS

DISCUSSION => Engine + Driveline => Topic started by: wazzu70 on July 14, 2009, 08:54:47 PM

Title: Difference between e30 and e36 M42 trans
Post by: wazzu70 on July 14, 2009, 08:54:47 PM

What are the differences between the e30 and the e36 transmission mated to the M42? I am looking for a M42 to swap into my e30 and found one out of a ti (compact) so I was just curious what the differences were. Are the gear ratios different, mounting tabs? Which is stronger?

I did a search and could not come up with anything so sorry if this is general knowledge around here. Im new to M42s.

Cheers,
Nick

Title: Difference between e30 and e36 M42 trans
Post by: Hodge on July 14, 2009, 09:25:09 PM

E30 M42's had the Getrag 240
E36 M42's had the Getrag 250

I would say the 250 is stronger, since it is also the same transmission used in the E36 325's.

It's a good tranny, but sometimes the 1:1 5th sucks on the highway. A 6th gear .83:1 would be perfect.

As far as I know, the 250 is longer than the 240 as well.

Title: Difference between e30 and e36 M42 trans
Post by: fabe on July 14, 2009, 10:29:37 PM

The ratios are complete different, requiring the corresponding final drive ratio...

on an E30 318is with the G240, the standard ratio is 4.10
on an E36 318is with the G250, the standard ratio is 3.45

I have the G250 fitted in my E30 318is, running a 3.15 final drive... The gearbox is smoother and pulls better then my previous G240 with 3.91 final drive set up.

BTW, the G250 uses the thinner ATF oil instead of the usual manual transmission oil...

Attached is the calculation sheet i adapted from Ove Kvam's sheet taken from his website.

The ratio for the E36 gearbox may not be 100% accurate, but the 5th gear ratio of 1:1 is definitely correct..

Title: Difference between e30 and e36 M42 trans
Post by: wazzu70 on July 14, 2009, 11:31:51 PM

Thanks for the information guys, much appreciated. Very informative answers.

Fabe, what modifications did it take to get the e36 transmission to fit? Does it bolt to the same crossmember? I can get the driveline shortened as I would like to rebuild it anyway.

My biggest concern with using the G250 is that I will not be able to bump the final drive ratio up enough after the turbo. I guess there is the higher eta gears available that would probably work well...

Title: Difference between e30 and e36 M42 trans
Post by: fabe on July 15, 2009, 02:05:58 AM

see this thread.. http://www.m42club.com/forums/showthread.php?t=3852&highlight=Getrag

in addition to what can be found in the above thread.
- I retained the E30 prop shaft, remove the locking nut (on the rear section of the prop shaft) to 'shorten' the shaft length. Not the ideal solution but that the only way other then physically shortening the prop shaft.

- The E30 shifter arm (aluminum rod) remained. Selector rod (the bottom sheet linkage)  needs to be shortened.

That's about it..