Diff options/opinions for swap

[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.

[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]

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 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 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]

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.

[static]

i like my s50/ZF/3.25lsd combo for every day driving, on highway and in the city.

[e30polak]

i heard 3.46lsd is also fun, a little too torquey for my taste

[ericzz]

3:46 is way fun
3:25 is great for spirited driving and daily use with highways .

[bmwpower]

3:46 is way fun
3:25 is great for spirited driving and daily use with highways .

Ok, but does it matter which transmission?

I'm either going with an E30 G260 or the E36 M3 transmission.

I want a rear end that is fun, but is also good on highways.

[matt]

Ok, but does it matter which transmission?

I'm either going with an E30 G260 or the E36 M3 transmission.

I want a rear end that is fun, but is also good on highways.

Of course it matters.

[bmwpower]

3:46 is way fun
3:25 is great for spirited driving and daily use with highways .

Which trans are you using?

[BeirBrennerE30]

Ok, but does it matter which transmission?

I'm either going with an E30 G260 or the E36 M3 transmission.

I want a rear end that is fun, but is also good on highways.

it actually matters a lot... decide on your transmission first! then pick a complimentary rear end.

fun and good on highways are mutually exclusive when picking a diff... a 4.10 would be fun.... a 3.15 would be good on highways

[bmwpower]

it actually matters a lot... decide on your transmission first! then pick a complimentary rear end.

fun and good on highways are mutually exclusive when picking a diff... a 4.10 would be fun.... a 3.15 would be good on highways

Ok... so which is better to have....E36 M3 trans or E30 G260? Longevity wise, performance. With the G260 I need a custom bracket, with the M3 trans I won't...those kind of thing too.

Which trans provides the most & less expensive options when picking a rear? I don't want to go one way and find out I only have a couple of options and they're all $$$.

[ericzz]

I am running an e36 trans . I did the swap with the 3:25 and after a few days went to a 3:46 and will not go back . I can cruise at 60 with a 3k rpm . I may have a tach that is not 100% but it's close! Go witht he 3:46 unless you spend 75% of the time on the highways


FYI I HAVE A 50,000 MILES LSD 3:25 FROM A 535IS FOR SALE .