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View Full Version : What diff do I use?


Clemente
09-15-2005, 12:51 AM
O.k. guys as most of you know I have a 98 M3 motor going into my 97 Ti. I was told that the M-roadster rear was the best, but know I'm having doubts. I was told by Azevedo Motorsports that a 1987 323 diff would be better than an M-roadster diff?? They said I would feel more power out of the 87 323! I will be using this car as a daily driver and occasionally some roadtrips, but I want that power there when I need it. What other diffs would work and why would you choose them? Any help would be appreciated.

aceyx
09-15-2005, 01:28 AM
there was no e30 323.

i would edit your posts' subject to read something about doing a swap. you'd get more feedback from people who have actually done it, and what they used.

Clemente
09-15-2005, 02:42 AM
I don't know why he told me a 323? I guess I'll have to call back and talk to Diego! The swap was easy! I just need to know more about the different diffs. This was my first BMW swap (not bad). Well anyone who actually knows about the diffs please post! Thank You!

aceyx
09-15-2005, 04:36 AM
i mean editing "what diff do i use" to "conversion help: what diff do i use" or something.

that way, people who have completed the motor transplant (and subsequently also upgraded the rear end) will be able to tell you specifically, their experiences and what they have done. clear?

96cali
09-15-2005, 07:03 PM
What was the stock M3 diff ratio- 3.73? Seems like more power with a little taller gearing would be a good compromise for local vs. highway.

Clemente
09-15-2005, 09:32 PM
Thanks guys! I found out that the E30 m3 diff works wonderful for this swap, the problem is I plan on putting the turbo on after I get back from SEMA, and I don't know if the E30 gearing is substancial for that. I have'nt really seen anyone with a Ti M3 turbo. I'm gonna slap the M roadster diff on and try that, and I'll also try the E30 M3, I will have to see which one feels right for me. Thanks for the help! I agree with you 96cali about the taller gearing, but if I do the turbo I will have to go with a lower ratio. Thanks again aceyx and 96cali.

cali-ti
09-15-2005, 09:40 PM
i forget, but isn't the e30 m3 diff ratio something like 4.10? if so, that's going to be way too high. again, if memory serves, i believe the mz3 and m coupe ratios are 3.23. talk to maurolin if you can (try PMing him). he was going to supercharge or turbo his swap. not sure what state he's at with it right now.

Clemente
09-15-2005, 09:47 PM
I will run the e30 m3 diff all motor and probably the mz3 for the turbo, unless there is a lower one possibly a 325? We'll see!

KIRASIR
09-16-2005, 07:55 PM
If you are planning to turbocharge your M3 motor, I would recommend against going higher than 2.93.

e30 M3 diff is definitely NOT the way to go. With 4.10 gearing your engine will not have time to build enough boost unless you are in 4th or 5th gears.

SL

I will run the e30 m3 diff all motor and probably the mz3 for the turbo, unless there is a lower one possibly a 325? We'll see!

sKunkman
09-18-2005, 09:57 PM
Yeah, I would have to say go with a taller gearing (lower number). I'm not sure what cars have what gearing, but a low, near 3.00 diff should be substantially better, especially with that kind of power in your car.

andy
09-26-2005, 10:58 PM
I think the Euro-only 87 323 had either a 3.64 or 3.73 rear end -- you will definitely feel a difference having a lower ratio rear end, turbo spooling notwithstanding.