540i Manual Transmission Rear differential upgrade!

[e39530i5speed]

Hi,
The 540i with manual transmissions has horrifically tall gearing. It has a 2.81:1 rear differential. I want to upgrade it to shorten the gearing. I know that 3.15:1's came stock on the 2003 M-Sport and M5 as well as all of the automatic 540i's. However, 3.15 isn't quite a large upgrade.
I look around and all of BMW's cars that use V8's such as the M62 and N62 of variety of sizes all tend to use differentials of 3.23 or 3.38. I think 3.46 is a bit too much, however 3.38 sounds reasonable as does a 3.23. These came on E60's and E65's 5&7 series cars.
I obviously want to buy a used open differential. I cannot however find anywhere if the flanges are interchangeable between differentials and if its a drop in replacement from the old ones meaning that they bolt to the frame in the same spots and you're good to go.
Thanks for any help!

[filon102]

I would just put the auto 3.15 into place, one (big) reason is because its a direct fit and nothing (to my knowledge) needs to be changed... if you really want to modify ur rear end i would just put e39 m5 lsd in the back :/

[topaz540i]

3.15 is about as high as i would go for street use. Im at 3k even in 6th doing 80mph on the interstate. Anything more than that and i would have to do my long distance cruising in the slow lane.

[TriniSpeC]

im in for an answer. im no expert, but i'll start with what I know, I beleive it goes by size, the Non-M cars use a 188mm diff case.

not sure about anything after this point.
http://www.ebay.com/itm/BMW-e36-rear-differential-3-91-LSD-ratio-medium-case-NICE-188mm-/171000660167?pt=Motors_Car_Truck_Parts_Accessories&hash=item27d06f00c7&vxp=mtr

this says 188mm, but I think its a 168mm
http://www.ebay.com/itm/93-BMW-E30-325ic-DIFFERENTIAL-LIMITED-SLIP-LSD-OEM-/230945570885?pt=Motors_Car_Truck_Parts_Accessories&hash=item35c56dc045&vxp=mtr

- - - Updated - - -

imagine a 540i with gears at the back........... 3.73... 3.91.. plus a lsd. oh man.

[LaLaRay]

3.15 is about as high as i would go for street use. Im at 3k even in 6th doing 80mph on the interstate. Anything more than that and i would have to do my long distance cruising in the slow lane.

i know right.. i wouldnt mind a 3.38 Lsd though :rolleyes

[cwise12]

The 2003 M-sport 6-speed did NOT come with a 3.15. Only the Auto did.

Going above 3.15 will start to destroy your fuel economy. I wouldn't go past it, IMO. I had to replace my differential, and I put an identical 2.81 in it for just this reason.

[donbruno]

subscribed cause i'm interested in this too. when i refinance in may, i'm hoping to have some extra funds that I might be able to do something like this. just to make sure i'm understanding things correctly, an M5 LSD would be helpful with acceleration because of the shorter(?) gearing and also the limited slip allows for more...colorful driving, yes?

[ahsm]

The 2003 M-sport 6-speed did NOT come with a 3.15. Only the Auto did.

Yes it did...

[James39]

Hi,
The 540i with manual transmissions has horrifically tall gearing. It has a 2.81:1 rear differential. I want to upgrade it to shorten the gearing. I know that 3.15:1's came stock on the 2003 M-Sport and M5 as well as all of the automatic 540i's. However, 3.15 isn't quite a large upgrade.
I look around and all of BMW's cars that use V8's such as the M62 and N62 of variety of sizes all tend to use differentials of 3.23 or 3.38. I think 3.46 is a bit too much, however 3.38 sounds reasonable as does a 3.23. These came on E60's and E65's 5&7 series cars.
I obviously want to buy a used open differential. I cannot however find anywhere if the flanges are interchangeable between differentials and if its a drop in replacement from the old ones meaning that they bolt to the frame in the same spots and you're good to go.
Thanks for any help!

1st gear in the 420G is 4.32, even with 3.15, you're getting close to a dump truck style 1st gear.

[Cereal]

That's when you start launching in second ?

[topaz540i]

I dont use first much anymore. Stock i had to slip it a little to take of in second or it would bog. Wih the 3.15 i just use second to launch most of the time and then my first shift isnt until around 40mph, its like a super tall first gear using second lol. And an added benefit is no more jerky one-two shift while trying to drive in traffic.

[JimLev]

I still start off in first gear, skip second gear, shift to third at about 10-15 miles an hour.
Hardly need to touch the gas in first to get rolling.
First is good to about 30 miles an hour wound out tight.
You're not doing your clutch any favors by starting off in second, even with 3.15 gears.

[e39530i5speed]

I would just put the auto 3.15 into place, one (big) reason is because its a direct fit and nothing (to my knowledge) needs to be changed... if you really want to modify ur rear end i would just put e39 m5 lsd in the back :/
Nah, I don't want an LSD, it's gearing is the same so acceleration is the same. LSD gives better traction, but I don't need that. I have plenty of traction for what I need.

3.15 is about as high as i would go for street use. Im at 3k even in 6th doing 80mph on the interstate. Anything more than that and i would have to do my long distance cruising in the slow lane.
Since you've done this modification, has the acceleration noticeable improved? Does your butt dyno feel faster? If 3.15 really does make a huge difference over a 2.81 than I'll probably settle. Thing is that I've driven sports cars with much shorter gearing than these things and after a while you get used to the constant shifting, but it gives you a lot of acceleration. Cars with 4-bangers that rev to 9,000rpm have ridiculously shorter gearing than anything we're talking about like an RSX Type-S.

The 2003 M-sport 6-speed did NOT come with a 3.15. Only the Auto did.

Going above 3.15 will start to destroy your fuel economy. I wouldn't go past it, IMO. I had to replace my differential, and I put an identical 2.81 in it for just this reason.
Actually that is false, it all depends on how you drive it. A 3.15 will place less load on the engine on your engine so if you keep it in similar rpm's or upshift sooner, you can actually get better fuel economy from being able to be in a better rpm range for a variety of speeds. Whether that method is executed right is a different story.

[LaLaRay]

Yes it did...
No it didnt.



You're not doing your clutch any favors by starting off in second, even with 3.15 gears.

Exactly, You guys should still start off in 1st.

[James39]

That's when you start launching in second ?

Then what is the point of installing steeper gears? Just so you can bypass first? I don't get it.

[e39530i5speed]

I always use first, but shorter gears allow for more power output by narrowing your rpm band closer to peak power. Thats the benefit in racing. For daily drivability, it allows for much torque-ier gears for much better acceleration.

[LaLaRay]

Lower gears = better/faster acceleration = Lower MPG.. :shifty

[Johnbennett103]

BMW's are geared for top speed. To drive in the US, you need taller gearing to really enjoy IMHO.

I have had some experience with diff gears. I changed my 1995 M3 S54 swap with a 4.10 LSD, and its great. Unfortunately my 6th gear syncro is fried, so highway cruising is maxed at 65 to 70 (who really goes 80? In CA or Texas sure, in the NE, no way). The car kicks ass on local roads.

I found an open 3.38 from an automatic for my 'new' 2005 545i, and it cost less than $300 shipped! This should be perfect as a 15% increase in torque. I cant wait to install.

[FastJohn]

If you're going to the trouble to change the diff, get the LSD. It's the one thing my 540 really would benefit from.

It goes like this - long ramp onto the highway, road is clear, roll on the power, and just about the time it starts to feel really good, the inside rear wheel slips. Aaaaugh! Nirvana denied, again!

I don't want to give up the tall gearing, mileage is surprisingly good, but I'd love to get a LSD with my present gearing. Can one swap the ring and pinion from the stock 540 diff into an M5 diff? Probably not...

[e39530i5speed]

BMW's are geared for top speed. To drive in the US, you need taller gearing to really enjoy IMHO.

I have had some experience with diff gears. I changed my 1995 M3 S54 swap with a 4.10 LSD, and its great. Unfortunately my 6th gear syncro is fried, so highway cruising is maxed at 65 to 70 (who really goes 80? In CA or Texas sure, in the NE, no way). The car kicks ass on local roads.

I found an open 3.38 from an automatic for my 'new' 2005 545i, and it cost less than $300 shipped! This should be perfect as a 15% increase in torque. I cant wait to install.

Yes! I want to know if that 3.38 will fit an E39. If it doesn't than maybe I can swap the rear cover assuming the bolt pattern is the same. If you have any info on that let me know!

[TriniSpeC]

No it didnt.



Exactly, You guys should still start off in 1st.

your not doing your clutch any favors period :)

[LaLaRay]

your not doing your clutch any favors period :)

Why is that?

[AK_5eries]

I don't think all auto 540is came in 3.15 gearing. I'm pretty sure mine is a 2.81. Is there any definitive way to check?

[LaLaRay]

I don't think all auto 540is came in 3.15 gearing. I'm pretty sure mine is a 2.81. Is there any definitive way to check?

All steptronic or whatever ya call it have the 3.15.

[Spirit Force]

Why is that?

Are you seriously asking this? :lol Longer the gear that your starting off means you need to slip the clutch more -> more wear. Take off in 1th and then in 4th and you'll see.. :D

[topaz540i]

Unfortunately my 6th gear syncro is fried, so highway cruising is maxed at 65 to 70 (who really goes 80? In CA or Texas sure, in the NE, no way).

I guess you have never driven in New Jersey. Even the tractor trailors cruize at 80 and thats in the slow lane. If you even dare get on the interstate, turnpike, or parkway doing less than 75mph your going to get run off the road.


Btw why do guys assume its bad for my clutch if i start out in second? Like i said i dont have to slip the clutch so what's the difference? With the 2.81 first gear is nothing more than to get the car rolling then you shift to second jerk. With the 3.15 its even more useless. The second gear becomes slightly taller than the stock first gear, the way it should have came in my opinion. With the 3.15 If you shift at 2,500rpm out of first your shifting at about 10mph this aint no 120hp honda civic lol. I dont know how hard this is on a stock 540's clutch with a 3.15 but mine isnt stock. Mine has plenty of torque to drive in traffic starting in second. In the rain i pretty much have no choice unless i turn dsc off or else i needless spin the tires at every red light.

[LaLaRay]

Are you seriously asking this? :lol Longer the gear that your starting off means you need to slip the clutch more -> more wear. Take off in 1th and then in 4th and you'll see.. :D

Dude wtf are you talking about... Im pretty sure he was talking to me about something totally different my man

[e39530i5speed]

Well from what I found out is that the E39 and E60's use the same 94mm input flange. The output flanges are different, but use the same splines so they can be swapped also. If the differentials themselves are different width then the swap will work according to my sources. Any help on this?

[Justin517]

I don't think all auto 540is came in 3.15 gearing. I'm pretty sure mine is a 2.81. Is there any definitive way to check?

I believe only automatics with the sport package after a certain date (face lift?) got 3.15 gearing.

NO 6-speed 540i's got 3.15, not even the 2003 M-tech as the OP states.

[aspensilver540]

LALA, manual expert dishing advice in 1 month
stalling at your local stoplight :)

[LaLaRay]

LALA, manual expert dishing advice in 1 month
stalling at your local stoplight :)

Lol heyyy what can i say guess a month is all i needed.. ;) and noooo I Stopped stalling all together like the 2nd week lol... But tisk tisk sheesh so many doubters... Looks like its time to make a Video of my skill :devillook

[e39530i5speed]

If I can in fact get the 3.38 in, I'll make a thread on that and how its done. I'm getting ready to pull the trigger. A manual 540i with a 3.38 will put into a different level of car instantly. With the current differential of 2.81, using my driven wheels (255/40/17) and a 6th gear of 0.85 than RPM's are at 2245rpm @ 70mph. With a 3.38 rpm's will be at 2700rpm which I think its completely fine. Considering I rarely go on the highway and my beltway rarely permits me to go over 65mph anyway due to traffic...its fine. Assuming a 6500rpm redline, top speed with a 3.38 is 168.5mph in 6th gear. Once again...an irrelevant and ridiculous speed.

[e39530i5speed]

Well...after searching and not being able to come up with any results and concrete answers, I pulled the trigger on a 3.15. No doubt a big difference and no doubt worth the money. If anybody is questioning weather the upgrade is worth it then stop thinking and get it.

[donbruno]

Congrats man...would you be kind enough to share the parts involved, their costs, labor costs and detailed impressions? And just when you thought we couldn't love our 540s any more, right? :)

[James39]

I still have one for $300 shipped if anyone else wants to get started :)

[cwise12]

Yes it did...

Think again.



Actually that is false, it all depends on how you drive it. A 3.15 will place less load on the engine on your engine so if you keep it in similar rpm's or upshift sooner, you can actually get better fuel economy from being able to be in a better rpm range for a variety of speeds. Whether that method is executed right is a different story.

On the highway, there's no debate over the fact that a higher overdrive ratio will yield increased fuel economy. Sure, accelerating you can treat the car however you want and get different fuel economies. However, having the engine spin faster at highway speeds will certainly not yield the same economy.




NO 6-speed 540i's got 3.15, not even the 2003 M-tech as the OP states.

Precisely. Thanks Justin.

[e39530i5speed]

Congrats man...would you be kind enough to share the parts involved, their costs, labor costs and detailed impressions? And just when you thought we couldn't love our 540s any more, right? :)

No problem! For $250 (shipping included) I bought the 3.15:1. Apparently, E38 and E39 use the same ones so that can widen your search.

Extra parts I got was the CV joint gasket. I also anti-seized all the bolts when reinstalling.

Regarding the swap itself, the input flange is identical which is excellent and the two output flanges just had to be yanked out and swapped. It may be a bit yard to pull out so you can use a flathead screwdriver and a hammer to help. Obviously make sure no dirt or dust gets inside.

The three subframe bolts can be a bit of pain to reach into and some bolts may be hard to un-screw (rust perhaps?).

Now, the differential itself is pretty damn heavy. I wouldn't be surprised if it was a 100lbs. I used an above ground lift and an adjustable safety jack to lower it and lift the new one inside.

Now...I am not quite confident in my motor mounts right now so I take it easy on the throttle and sudden throttle when I test it. And I can't do my mounts until I do my valve cover and upper timing cover gaskets, because they are leaking a bit onto the mounts which isn't good for the rubber. So I'm speaking from applying steady throttle.

There is no doubt a big difference. Absolutely worth the money. Pulls well in all gears. 2nd and 3rd where most driving is done are VERY awesome. The difference isn't day/night like a 3.38 would have been, but well worth it.

Honestly, the rpm increase isn't huge and yet the acceleration is so much better. Makes me feel like the car should have had this ratio as stock.

Oh and you can cruise slower in 1st gear when in traffic without stalling which is nice and you also have to slip the clutch a lot less when getting moving. 1st gear is still a very useable and long gear.


I've actually driven an M3 E46 with a traditional manual, not SMG and I don't know if its quicker or not TBH, but the Butt Dyno on the 540i feels better. Seeing as the 540i's are heavily under-rated and show great improvements with only bolt-ons, perhaps they can compete? Not sure.

If you have any other questions please ask. 100% recommend.





On the highway, there's no debate over the fact that a higher overdrive ratio will yield increased fuel economy. Sure, accelerating you can treat the car however you want and get different fuel economies. However, having the engine spin faster at highway speeds will certainly not yield the same economy.


Then why not just put an overdrive of 1.5:1 instead of 2.81:1.

Oh and the 2003 does appear to have the standard 2.81. Mixed information all over though.