Diff options/opinions for swap

[matt]

OK, first you'll need the gear ratios for the different transmissions. They're basically proportional, so we'll just consider 5th gear.

Getrag 260 - .81:1
e36 transmissions - 1:1

Then you go here: http://www.f-body.org/gears/

And plug in the data and it will show you your speed vs rpm table for 5th gear.

I would pick a speed (60 or 80 work well) and change the gear options. (mix and match) then compare the results. There are lots of other online calcs that will graph it for you and such, this was just the first one I came to.

[bmwpower]

You cannot bolt the e36 diff case into an e30. You will need to move the guts from the case into an e30 case.

Do math.

Maybe somebody with a stock eta would run a 3.25 with a getrag 260. That diff works wonderfully with an e36 getrag or ZF in a swapped car.

Whoops.

I don't know how.

Going to look back again, but I could have sworn otherwise.

thx

[matt]

You cannot bolt the e36 diff case into an e30. You will need to move the guts from the case into an e30 case.

Do math.

Maybe somebody with a stock eta would run a 3.25 with a getrag 260. That diff works wonderfully with an e36 getrag or ZF in a swapped car.

[bmwpower]

You know you'll have to swap the R&P to fit a 3.15 into an e30, right?

Have you done any math to figure out your RPMs in 5th at 80 or anything?

Of the options you posted, only the first two make any sense for an NA car.

R&P? I know I have to swap the flanges and the rear cover.

I haven't done any math.

I thought people were running the G260 with a 3.25? I saw a bunch of recommendations about that diff. Maybe not S50 specific, but I didn't think that mattered.

[matt]

You know you'll have to swap the R&P to fit a 3.15 into an e30, right?

Have you done any math to figure out your RPMs in 5th at 80 or anything?

Of the options you posted, only the first two make any sense for an NA car.

[bmwpower]

Having never messed with diffs....So which differential/trans setup do I go with:

#1
S50
E36 M3 5spd. trans
3.15 LSD diff

#2
S50
E36 M3 5spd. trans
3.25 LSD diff

#3
S50
G260 trans
3.15 LSD diff

#4
S50
G260 trans
3.25 LSD diff


The 3.15 would be from a 95 M3 as is the trans and engine.

I'm looking for the best balance. Nice acceleration, but still have nice cruising on the highway.

Any others to consider? 3.46? I have to narrow it down somehow.