Does this sound right to you? M50, diff and tranny question...

[MIKe30]

ok, i am actually in VA right now in a hotel room on the way back from picking up my newly acquired e30 from tennessee...

anyway, point of this thread is this...

i have m50b25, the tranny is a getrag from an e36, and the diff is a 3.25lsd.

normal combo for m50 swapped e30's right?

well thats what i thought, until i find out that at 80mph i'm at 5500 rpms in 5th, and i completely run out of gearing at 100mph at 7k in 5th...

what gives?

i thought this was a popular combo... dont see how if the gearing is like this...


maybe i just need a 6th gear lol...

what are you guys running?

[FredK]

Your calculations are off. You should be turning around 3700 rpm at 80 mph with that combo, assuming stock tire size of 195/65 R14.

Your gear limited speed will be close to 150 mph. I'm sure the M50B25 would run out of puff long before that happens, but it's always nice to know that kind of info. :D

[Jean]

Wait, you sold your old e30 and got one with the m50 already in it ?! NOICE!

With the 3.25 (1 to 1 5th iirc), you should be under 4k @ 80.

[FredK]

Um, oops, I misread that. You are already IN an M50 swapped car. ;)

My guess is that if you bought a 318is M50, the original swapper did not change the cluster coding plug, and it is off by a factor of 1.5 (4 cylinder vs 6 cylinder).

So when you are turning 5500 RPM on the cluster, the engine is actually turning 1.5 times slower, which is 3666 RPM.

You'd need a 4.90 diff in order to be turning 5500 RPM at 80 mph.

[Jean]

x2 on the cluster plug. When I tested a 325i cluster in my 318i, car would not rev all the way with the wrong coding plug in it.

[MIKe30]

Your gear limited speed will be close to 150 mph. I'm sure the M50B25 would run out of puff long before that happens, but it's always nice to know that kind of info. :D

you'd be surprised, my m20 had gotten up to an indicated 146... granted it was on 205/60/14's but still an m20 nonetheless (of course it was by a professional driver on a closed course )

Wait, you sold your old e30 and got one with the m50 already in it ?! NOICE!

yup :p

Um, oops, I misread that. You are already IN an M50 swapped car. ;)

My guess is that if you bought a 318is M50, the original swapper did not change the cluster coding plug, and it is off by a factor of 1.5 (4 cylinder vs 6 cylinder).

So when you are turning 5500 RPM on the cluster, the engine is actually turning 1.5 times slower, which is 3666 RPM.

You'd need a 4.90 diff in order to be turning 5500 RPM at 80 mph.

freakin awesome!! i feel so relieved! on the rest of the way home today (7hrs today) i was thinking about it and thought perhaps it was a mistagged 3.46 or something... thought i was gonna have to swap the dif

x2 on the cluster plug. When I tested a 325i cluster in my 318i, car would not rev all the way with the wrong coding plug in it.

great. so if i swap a 325i cluster in it i should be all good? (i kinda dont wanna just change the plug because the current cluster is pretty shot. the miles it turns over are about a 1/3 of the actual miles traveled. i hope it hadnt been like that for too long and i wonder if the PO knew about it.)


btw, you guys are so much help :bow:

edit: and do you know if there is a rev limit? i was scared the first time the needle shot past 7k i thought i was gonna break something... it just moved so fast (like 1.5 x as fast lol)

[Mr.SWISS]

So where are the damn pics at?
BTW that is the combo I am running(M50+E36 trans+3.25LSD)

[MIKe30]

So where are the damn pics at?
BTW that is the combo I am running(M50+E36 trans+3.25LSD)

pics are on bf.c mang

[MIKe30]

So where are the damn pics at?
BTW that is the combo I am running(M50+E36 trans+3.25LSD)

whats your 5th redline at? mine seems to redline at 125ish... yours the same?