Diff choices in M42 cabrio

[txleadfoot]

My '92 318ic has a 4.27 open diff with a stock, chipped M42. Has anyone swapped to a lower ratio rear-end without causing weird shifting issues in regards to available torque? My last car was a '91 318is with 4.10 diff and damn, this cabrio accelerates like a tank in comparison (300# difference). I'm guessing if I go lower ratio, that's gonna kill acceleration in favor of less revs on the highway. What's available out there PnP?

[tjts1]

Anything is available. It depends what you want out of the car. I use a 3.64 in my 318i sedan but it is lighter than the convertible. I think a 3.91 would be a good choice in your case.

http://www.m42club.com/forums/showpost.php?p=26477&postcount=28

[BMWLA]

The ic is a lot hevier than the is are you sure that it has a 4.27 tho?

[CorvallisBMW]

The ic is a lot hevier than the is are you sure that it has a 4.27 tho?

All late-models 318iC's had a 4.27, yes.

I know a guy running an OBD1 S52 through a ZF and the stock 4.27 in his 318iC. 1st and 2nd gear are completely useless, and he tops out at like 85mph...

But it will snap your fucking neck off if you have the guts to WOT it

[KenC]

I'd try and find a 4.10 LSD. You can run a small case with the M42 as well.

[Hick]

3.73 in a 318is is very nice. im sure you could get away with the same diff in a cabiro despite the extra weight.

[txleadfoot]

Hmmm....small case?

I will look into that. Is that a small case and what model was it available from at the factory?

3.73 in a 318is is very nice. im sure you could get away with the same diff in a cabiro despite the extra weight.

[tjts1]

All 4 cylinder E30s sold in the US had a small case diff. These have 6 bolts on the diff cover. The small case ratios available are 4.27, 4.11, 3.91 and 3.64. There was a 4.45 and 3.45 small case diff in the E36 318ti which is also compatible. The 8 bolt medium case diff is also a direct swap into your car. That one is available in about 10 different ratios which I'm not going to list. I'm on the hunt for medium case 3.73 LSD at this point.

[Hick]

3.73's are VERY common. Most 325i/s had them.

[naplesE30]

I have 3.73 lsd in my 318is and love it.... Much better on the highway than my open 4.10

[txleadfoot]

how does it perform from a stop? curious about city driving.

[Hick]

better than the 4.10ls

i autox this thing, its WAY better for the car.

[tjts1]

These cars should have had a 3.73 from the factory. There is nothing to gain from a 4.10 or 4.27 in the real world.

[///M42 sport]

What diff for efficiency?

[marksv4]

my diff in my 91 cab has a 2.93 open......