thinking bout new diff maybe a 338?

so the time has finally come to where I can put a little more money into my car..
I've always wanted a bit more torque and am starting to realize a new diff would be probably be my best bet. I have an OBD1 so I'm thinking a 223 or maybe even 338 or higher??

what I'm really asking is for some feedback of those who have done this swap.
some pros and cons (obviously higher gear so MPG will be taking a fall...) looking for more specific stuff.

anything helps

I'm not 100% sure on what I have in mine but I think it is a 3.23.

Check out this spreadsheet. Bimmerfest won't let me attach xls files so I renamed it to pdf.


RENAME THIS FILE BACK TO XLS TO USE IT.

HERE is a listing of all the available gear ratios for a few different models including the E36 M3. I'm running a 3.38 in my 5 speed M, it's a riot to drive everywhere except the highway where it winds out pretty high in order to maintain speed.

That's the thing. I'm cruising at 70ish at 3000rpms with a 3.23. A 338 would be even more revs. Great for autox etc. but not for road trips or autobahn type jaunts

Exactly. While my daily was down for repairs I drove the M for a while. She was a little on the thirsty side when running down the interstate, but then again I was having so much fun driving her instead of the boat that I didn't mind.

Hey guys thanks for the quick responses!

and I tried to take a look at that spread sheet but it wouldn't download properly =/

I'm in hard situation here... HAHA

I drive about 70 miles on the M a day. Mostly HWY driving with about 15 miles of nice city driving.... I usually put it in cruz control at 75mph on the freeway and wait for the twisties to come up towards the end of the drive right before the exit to home . So I drive both city and freeway alot..

since you have 338 in yours already could you give me an idea of where your RPM's fall at on the freeway and in different gears etc??
also is it an OBD1 or 2? because I know considering the difference of engine there would be a difference.

thanks guys!!

S50 powered OBD1. The M has been in storage for a few months, but last time I drover her into work rpms sat rather close to 4 grand on the interstate (limit is 65 around here, I usually only run 5 or so over the limit).

http://www.diffsonline.com/techinfo/...Calculator.xls

There's the direct link.

that spread sheet is soooooooo helpful thank you!

Yea, man. Sorry I couldn't attach it to the thread like I wanted before. Combine that spreadsheet with the info on Bokchoys that the ECS rep linked and you can see what swapping out from other E36s will do.

hummm been doing some more research bout the diff swap.

is it really worth the 500$ (diff) from swapping a 3.15-3.38
-am I really going to notice much of a torque/power difference?

after seeing the spread sheet my concerns as far as rpm with the 3.38 are really minute ..
maybe I should consider going higher.

240 poounds-feet x 4.20 (1st gear) x 3.15 (final drive) = 3174 pounds feet delivered to rear wheels

240 poounds-feet x 4.20 (1st gear) x 3.38 (final drive) = 3407

(3407 - 3175)/3175 = 7.3% increase

A 7.3% increase in torque delivered means a 7.3% increase in acceleration.

Originally Posted by 95 ///M3

hummm been doing some more research bout the diff swap.

is it really worth the 500$ (diff) from swapping a 3.15-3.38
-am I really going to notice much of a torque/power difference?

after seeing the spread sheet my concerns as far as rpm with the 3.38 are really minute ..
maybe I should consider going higher.

Get a 4.11!

Originally Posted by petriej

Get a 4.11!

or a 4.44 from the 318 auto then rebuild for LSD I'd do it if I had enough free time.