Diff Swap - possible perfomance changes? - United Bimmer Community

**QcMarque** · 01-10-2009, 05:07 PM

So I've been driving a '90 525i AT (has the 4.1 LSD diff), just bought a '90 535i MT (has the 3.65 diff I believe)... question being, if I put the 4.1 LSD into the 535 what type of performance changes should I expect? The car already has the performance ECU upgrade, and I do plan on other various tweaks and whatnot when $$ allows. But as of now I wanted (kinda need) to put a new/better cond. diff into her (current one whines when under a load aka slowing itself down - when putting the gas to it she's quiet.)

Thanks everyone! I've missed you all, but the new man of the household has been taking up my time - anyone interested in pics let me know and I'll put up the shutterfly link to all his pics.

**Radix325i** · 01-10-2009, 07:06 PM

Hello, first, I do not know a relationship with a spread so big (4.6), the biggest I know is 40:9 (4.44).

Anyway, If you put 525i's in 535i, You will get more troque, more acceleration but lower end velocity.

If you do a swap, you could get more speed on your 525i, but at a lower rate of acceleration.
I do not know if your 525i has an M20 or M50 engine, This year (1990) came with the 2 versions of engine.

E34 525i (M20)
I=40:9=4,44
I=43:11=3,91

E34 525i (M50)
I=42:13=3,23
535i
E34 535i (M30)
I=40:11=3,64

I hope give you some help.

USA manual:
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101211551
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101212567 ENDED

USA automatic:
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101211551
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101212567 ENDED
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=41:10=4,10 33101212733

Europe manual:
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=40:11=3,64 33101211549
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=40:11=3,64 33101212294
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101211551
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101212298
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101212298
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101211551

Europe automatic:
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=41:11=3,73 33101211835 ENDED
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=41:11=3,73 33101212296 ENDED
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=41:11=3,73 33101211835 ENDED
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101211551
01 RMFD FINAL DRIVE, VISCOSE DIFFERENTIAL I=43:11=3,91 33101212298

**QcMarque** · 01-11-2009, 02:31 AM

Yeah, it was a typo on the 525's diff... it has the 4.1 in it. Problem being (with driving the 525) is some idiot ran a red light and I clipped him, then he drove off. There's damage to the front of the car and the electrical is dieing (wipers stopped working, no power options, no stereo, no computer, etc...) so I got the 535 to replace it... but the rear diff has been worn and now it howls when the car coasts in gear. I'm not worried about max mph. so much, as long as I can get up to 100 I'm happy.