3.15 Differential in 540i - Thoughts?

[AquilaBMW]

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

Pretty sure it's a 3:15, not 3:46 Diff on the 540iT & Sport Model.

[topaz540i]

Cast iron doesnt really corrode worth a damn.

Oops small oversght. Well, i guess that was a waste of money then.

[LaLaRay]

Im pretty sure now that ima just buy a Dinan 3:45 lsd diff.... F*ck it, Go hard or go home right....

http://dinancars.com/shop/D773-0390-...al.aspx#page=2

[noodlesandsam]

Aquila is right. Wagons got 3.15. Nothing higher

[topaz540i]

I know where there is a used m5 lsd with 3.45 gears for $900

Correction: now $825

Bastards i offered $800 and th ey never responded.

oops double correction: i read the ad wrong. its a 3.15 that was removed because they switched it for a 3.45

[jburnham]

You guys are missing the point. A 3.15 diff, open or LSD is a must for a 540i/6. My 540i/6 started out with the 2.81. For daily driving around town, the time spent driving a particular speed isn't evenly distributed. Due to speed limits, traffic, etc, you'll spend the majority of your time driving +/- a few mph of 35, 45, 55 etc. I made up the speeds, but you get the idea.

With the 2.81 gearing, I always felt like the majority of the time I was hunting for/switching gears to be in the sweet spot. Switching to the M5 diff made a world of difference. It feels like I'm always in the RPM band where I'm not burning too much gas, but can still access the power.

I recently moved the M5 diff in to my 540iA and put the iA 3.15 diff in the 540i/6. Unless I'm on the verge of spinning a tire, the iA diff has all the benfits of the M5 diff and the 540i/6 is still awesome.

[LaLaRay]

I know where there is a used m5 lsd with 3.45 gears for $900

Correction: now $825

Bastards i offered $800 and th ey never responded.

oops double correction: i read the ad wrong. its a 3.15 that was removed because they switched it for a 3.45

Holy batman i was about to flip out! Lol i was about to pm you asking where! And buy it this very instant.. i woulda told him ill go 100 over any offer he got

[AquilaBMW]

I have driven various cars with 2:82 or 3:15 Diffs. I personally prefer the 3:15 with the V8s. I like the power band it keeps the car in and the take off from dead stop is much improved.

All E38 M-Sports came with the 3:15 and what an amazing difference it makes on those cars. It makes the E38 perform with quite a bit off dignity off the mark.

My DINAN sadly doesn't have a 3:15 Diff and in my opinion it is a weak point in the car's performance. When merging on freeways or coming up to speed I pretty much have to mash the throttle to get it to really fly. With the 3:15, the pick up would be much improved.

I am not sure what the calculation of MPG is for 500 more RPM higher while cruising, but I am pretty sure it would be marginal - especially on the V8s.

I vote for at least a 3:15 any day. I have driven a car with 3:46 - not for me!

[topaz540i]

I only finished the install last night but i can tell you my car went from sports car swift accelration to brute muscle car violent.

[Justin517]

I only finished the install last night but i can tell you my car went from sports car swift accelration to brute muscle car violent.

Yup, pretty much the best mod for the money.

[528canyonrot]

So what is the part number for the LSD 3.15 http://realoem.com/bmw/showparts.do?...41&hg=33&fg=05 realoem shows three differentials but doesnt say which of the two 3.15s is LSD?

[sicarius82]

So what is the part number for the LSD 3.15 http://realoem.com/bmw/showparts.do?...41&hg=33&fg=05 realoem shows three differentials but doesnt say which of the two 3.15s is LSD?

The second and third ones have the same part number and I clearly see where it say's the 3.15 (I=3,15).

I'd just get the M5 version (33102229566) and be done with it.

[ninetyseven1]

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[ninetyseven1]

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.

You will not hit redline at a lower rpm than before. Redline is redline , that wont change. What changes is you will get to redline faster than before in each gear.

[JimLev]

You will not hit redline at a lower rpm than before. Redline is redline , that wont change. What changes is you will get to redline faster than before in each gear.

He said you'd hit redline at a lower MPH, not at a lower RPM.