3.62 Diff Gear Upgrade using E46 M3 Ring and Pinion - The Unofficial BMW M5 Messageboard (m5board.com)

RUFM5 · 2nd September 2007, 17:16

Hey guys new owner here!

I plan on changing my OEM 3.15 gears to 3.62 using the direct swap of OEM E46 M3 ring and pinion. My mechanic confirmed this can be accomplished and while the work is performed the seals and certain internal components will be swapped such as the seals, crushed sleeves, bearing and shims.

Used ring and pinion costs $200 and labor is about 8 hours. Total estimate of about $1000.

Has anyone else performed the swap instead of buying Dinan's $2500 differential?

Need4Spd · 2nd September 2007, 19:34

This is the first I've heard of this mod, but perhaps the question should be "why"? 3.62 seems like awfully short gearing for a V8 that is more rev limited than the M3 engine's 8000 rpm redline, and has far more torque. Aren't you worried about making 1st gear almost uselessly too short, and actually making your 0-60 times longer by needing an extra shift? I'm not saying this is necessarily a bad idea, but the Dinan gear set is 3:45 and perhaps so for a reason. The M5 isn't really suited for drag racing, which is often the reason for going to very short gears.

Madduc · 2nd September 2007, 19:55

First off I would NEVER use a USED set of gears. I know of somebody who has the 3:62's and they are some very short gears. He has been questioning going down to the 3:45's.

RUFM5 · 3rd September 2007, 00:12

Quote:

Originally Posted by Need4Spd

This is the first I've heard of this mod, but perhaps the question should be "why"? 3.62 seems like awfully short gearing for a V8 that is more rev limited than the M3 engine's 8000 rpm redline, and has far more torque. Aren't you worried about making 1st gear almost uselessly too short, and actually making your 0-60 times longer by needing an extra shift? I'm not saying this is necessarily a bad idea, but the Dinan gear set is 3:45 and perhaps so for a reason. The M5 isn't really suited for drag racing, which is often the reason for going to very short gears.

Several people have opted for the Dinan or Evosport 3.91 gears and reported increase in noise. I feel that these are too short and 3.62 is perfect according to Evosport's 3.64 kit. My mechanic said used gears are fine as they will somehow be repolished in the installation process.

"Give your E39 M5 the additional torque it needs with our upgraded 3.64 or available custom gearing (call). The new 3.64 gears alone add almost 10% additional torque to the rear wheels. With a negligible loss in top speed and engine speed, the upgrade delivers awesome and instant acceleration and exit speeds making this the "best-bang-for-the-buck" upgrade for this car."

mottati · 3rd September 2007, 02:22

he 3.91m5 gearset is for the e60. I have the 345s and they are totally fine day to day. 364s might be a little short, but that's cheap enough to experiment.
my e34 has 391s (oe) and that too is really ok on the highway.

stilov · 3rd September 2007, 03:42

I have been thinking of this too...I'd like tp get some snap put back in the car... I am a mile high elevation.
I can't find a shop that'll do it. I wonder if I can do it myself...I am very mechanically inclined...diffs are one if the only things i haven't done.

Lscman · 3rd September 2007, 19:33

Quote:

Originally Posted by RUFM5

............I plan on changing my OEM 3.15 gears to 3.62 using the direct swap of OEM E46 M3 ring and pinion.....

Why?

The first gear ratio is already too deep for full throttle launch with street rubber. Deeper gears will only aggravate the issue. Acceleration will not improve unless you install slicks and that will quickly tear out your flimsy aluminum subframe. Who needs or wants a creeper gear in an M5 to improve torque multiplication at walking speed? I think another overdrive is more useful.

You're turning your M5 into a Hummer.

Need4Spd · 3rd September 2007, 20:14

Quote:

he 3.91m5 gearset is for the e60. I have the 345s and they are totally fine day to day. 364s might be a little short, but that's cheap enough to experiment.
my e34 has 391s (oe) and that too is really ok on the highway.

That may be, but make sure you compare the gear ratios of the transmissions, too. The car that comes stock with shorter rear end gears may have a taller final gear in the transmission. Also, cruising along the highway at 3200-3400 rpm with a 6 cyl engine qualitatively may feel more comfortable than doing that with a torquey, more rumbly V8.

To restore torque at higher elevations, gears help, and are less money than a turbo or supercharger, but have their drawbacks in really shortening your first gear if overdone. If I lived in a high elevation area, much as I like my M5, I'd be tempted to switch to a turbocharged car, either a current 335i or one of the Audi turbos.

RUFM5 · 4th September 2007, 19:53

Here is an older thread with references to the 3.62 gearset. Getting 3.45 diff installed NOW! ill let u know... http://www.evosport.com/product/prod...RV.B39.364.DYN

stilov · 6th September 2007, 16:43

will you ask your mechanic where he is getting the crush parts, seals, etc. I will be doing this myself. I just need some direction on where to get the parts.