3.15 Differential in 540i - Thoughts?

[verite]

Anyone out there do a differential swap on the 540i? Thoughts?

I have an 02 540i/6. Pardon what may be a stupid question, but wouldn't the shorter gearing on the differential just be equivalent to you holding your shifts for longer / revving higher?

Not in 1st or 6th gear of course - but for the gears in between...

[NervoS]

Downside: you'll have shorter 1st and higher rpms at 6th (more gas consumed).
Upside: more torque, better acceleration.

[topaz540i]

if you use an auto 540 i believe certain years had 3.15's

but if you use one from an m5 its not only 11% tighter gearing but also the benefit of limited slip.

[James39]

Hit me up if you want a nice 3.15 open diff Came from an iA car, works very good, mileage less than 100k

[TriniSpeC]

and if you have it gold plated you can be a baller like topaz

[topaz540i]

its purely for corrosion resistance.

[e30ultimate]

what do used open 3.15s run around here? A buddy of mine has a few that I may help him dispose of. i know shipping would prob run 60-80$ at least though.

[topaz540i]

Check either ebay or the classifieds section on this site for comparisons

[E39 Sean 540ia]

That is a beautiful differential Topaz. I read your build thread, nice work.

[topaz540i]

unfortunately the only person that will ever see it is the guy at the alignment shop

[Justin517]

I wouldn't bother going to 3.15 open unless its all you can find and your 2.81 is shot. Adding more mechanical advantage (3.15 vs 2.81) but no additional grip (LSD) isn't the best idea in a vehicle that already breaks traction fairly easily.

[ninetyseven1]

Anyone out there do a differential swap on the 540i? Thoughts?

I have an 02 540i/6. Pardon what may be a stupid question, but wouldn't the shorter gearing on the differential just be equivalent to you holding your shifts for longer / revving higher?

Not in 1st or 6th gear of course - but for the gears in between...

Nothing to do with holding shifts longer or revving higher. It will cut the mph of each gear,but get you down the road quicker and usually about a car space or two ahead of where you were with the old rear. You will be at a higher rpm while cruising at like 60 on the highway tho. So if you were at 2300 rpm at 60 with your stock rear ,then going to a 3.15 rear you may be at like 2500 rpms at 60 mph now. You will notice the biggest difference when taking off from a stop. You will be about a car space ahead of where you were before,but you may only be able to hit 25 mph in first gear at the max now. Get it?

[Only1Balto]

if you use an auto 540 i believe certain years had 3.15's

but if you use one from an m5 its not only 11% tighter gearing but also the benefit of limited slip.

Do want....

[ninetyseven1]

what are you talking about "tighter gearing"? a 3:15 ratio is a 3:15 ratio. The m5 is a limited slip version though,giving better traction.

[Firefighter3244]

I would love a 3.15 lsd, But $600+ can be better spend on so many things for ME.

^^ By Tighter gearing he just means that its... tighter, Shorter, Not as long as the 2.xx

Not to thread jack, But are there any other options? From say a 7 series, Or anything?
Didn't know if 3.15 is the shortest option.

2300 vs 2500 rpm is nothing for the low end performance you gain.

My friends domestic has a 4.10 rear and in 1st (Auto) is dips the rear end of the car....

These are NOTHING compared to my Japanese Tranny I had shipped over for my Honda, 5,400 RPM at 75mph. :

It's also Nothing compared to the e39. Gah I love our 540I/6's!

[topaz540i]

what are you talking about "tighter gearing"? a 3:15 ratio is a 3:15 ratio. The m5 is a limited slip version though,giving better traction.

By tighter gearing i mean vs stock gearing which is 2.81.

The observed difference will be faster acceleration but each of the individual gears will hit redline at a lower mph than before. Squeeze the gears tighter you get more acceleration with a lower top speed. Open the gears up you get a higher top speed but less acceleration.

Kinda like changing the sprocket size on your bicycle.

[ninetyseven1]

I would love a 3.15 lsd, But $600+ can be better spend on so many things for ME.

^^ By Tighter gearing he just means that its... tighter, Shorter, Not as long as the 2.xx

Not to thread jack, But are there any other options? From say a 7 series, Or anything?
Didn't know if 3.15 is the shortest option.

2300 vs 2500 rpm is nothing for the low end performance you gain.

My friends domestic has a 4.10 rear and in 1st (Auto) is dips the rear end of the car....

These are NOTHING compared to my Japanese Tranny I had shipped over for my Honda, 5,400 RPM at 75mph. :

It's also Nothing compared to the e39. Gah I love our 540I/6's!

-

[ElleShooTiger]

Every time I get a sad that my 2003 540i Sport doesnt have a 6spd, I'm forever grateful that BMW gave us the 3.15 differential as a consolation prize.

its purely for corrosion resistance.

Cast iron doesnt really corrode worth a damn.

[LaLaRay]

540 sport automatics came with 3:15... You can buy mine

[Justin517]

Every time I get a sad that my 2003 540i Sport doesnt have a 6spd, I'm forever grateful that BMW gave us the 3.15 differential as a consolation prize.



Cast iron doesnt really corrode worth a damn.

That was just an attempt to keep acceleration performance between auto and manual similar, as the autos make 25-30 less whp than a 6speed due to the extra parasitic loss of the auto.

[Cyrix2k]

Anyone out there do a differential swap on the 540i? Thoughts?

I have an 02 540i/6. Pardon what may be a stupid question, but wouldn't the shorter gearing on the differential just be equivalent to you holding your shifts for longer / revving higher?

Not in 1st or 6th gear of course - but for the gears in between...

yes, this is correct. 2.81 is better for a DD, 3.15 is better for sportiness.

[LaLaRay]

That was just an attempt to keep acceleration performance between auto and manual similar, as the autos make 25-30 less whp than a 6speed due to the extra parasitic loss of the auto.

Lol

[e30ultimate]

The 540i station wagon (touring) has a 3:46 ratio. Look on ebay for $200 differentials

o really....... i know this 5 of mine is supposed to be my daily but... why not already has the 3.15 in there

[mithoangel]

The m5 is a limited slip version though,giving better traction.

[bdiefAZ]

I installed a 2.93 from an e38 740 in my 97 540, made a minor difference in acceleration, but did not have an impact on mileage.

If using an e38 diff, you must change the rear cover to the e39 cover for installation, great time to inspect internal components as well.

The 2.93 diff was free, the 3.15 would be a better swap, a 3.15 LSD even better.

Topaz - nice job sir