DIFF upgrade?

[Trentklein]

Just curious, has anyone on here upgraded their e38s diff? Worth it? If so, how much and what diff??

[board57796]

Just curious, has anyone on here upgraded their e38s diff? Worth it? If so, how much and what diff??

I replaced the diff in my 750iL with a 3.15 model from a 740i Sport. Paid $200, did the install myself. Nice upgrade from stock.

[Jamos]

Are there higher ratios available?

[Trentklein]

Are there higher ratios available?

Also wondering this. Just curious what the best would be for the car.

[GSXRliterbikz]

Yes there are other ratios available. But they are pricey. Like over 2k pricey.

[Trentklein]

Yes there are other ratios available. But they are pricey. Like over 2k pricey.

Woah ha that's out

[DUDMD]

I have gears that can be installed into an e38, 3.46 gearing.
I'm considering building a diff with them

Sent from my iPhone using BF.com

[danb1979]

Quaife do diffs for the E38; not cheap though:

http://www.ebay.co.uk/itm/Quaife-BMW-728i-Auto-E38-LSD-Diff-ATB-Limited-Slip-Differential-Kit-/380818000959

[Trentklein]

I have gears that can be installed into an e38, 3.46 gearing.
I'm considering building a diff with them

Sent from my iPhone using BF.com

Nice! Let me know how that goes if you do end up building one.

[kouks]

For those that have swapped to the Sport 3.15, does it require any updating to the DME since the engine speed and car speeds will be different?

[TxDarth]

For those that have swapped to the Sport 3.15, does it require any updating to the DME since the engine speed and car speeds will be different?

Think about it...the speed readings come from the wheels so the rear end will not make a difference.

[007008]

No software change needed. The rpms will be different but it's within the tolerance so the cruise control works fine.

[cody3]

Just curious, has anyone on here upgraded their e38s diff? Worth it? If so, how much and what diff??

I had a Dinan 3.45 LSD until it burned (don't ask) up and now have 3.38 LSD from Jim Blanton at Performance Gearing ( http://www.performancegearing.com/pricing.php). Not cheap, but lots of fun :)

[Sobek]

I'm not sure on pricing or sources, but if you can grab the diff out of a 730, 735 or (I think) 728i, they use a 3.23:1 diff - more than even the 740's 'sport' version. No idea about fitment, if there's anything special needed to bolt one up, but they'd certainly be a damn sight cheaper than buying a new / aftermarket diff I think.

[deathsled]

I've been doing a lot of research on this topic and here is what I have put together from the mess of threads out there:

The 1995 E38 is the only year with the normal 210mm "large case" diff. 96 and up cars have a redesign that use 215mm internals. The later diffs you are not going to find gears for aside from the 3.15 sport options. LSD units for the later style 215mm diff are aftermarket units and very pricey. There is no OEM option.

If you obtain a 1995 e38 diff you can swap in the internals from other 210mm large case differentials like an e39 M5 (3.15 lsd), an e46 m3 (3.64 lsd), etc.

The 1995 diff is a little longer than the others so if you switch to it you have to shorten your drive shaft or....wait for it...use a 1995 drive shaft.

I will be sourcing a 1995 diff to use for its case and shoving e46 m3 internals inside.

[danb1979]

Can I ask what the point is though of changing the diff in our E38's?!

[Trentklein]

I've been doing a lot of research on this topic and here is what I have put together from the mess of threads out there:

The 1995 E38 is the only year with the normal 210mm "large case" diff. 96 and up cars have a redesign that use 215mm internals. The later diffs you are not going to find gears for aside from the 3.15 sport options. LSD units for the later style 215mm diff are aftermarket units and very pricey. There is no OEM option.

If you obtain a 1995 e38 diff you can swap in the internals from other 210mm large case differentials like an e39 M5 (3.15 lsd), an e46 m3 (3.64 lsd), etc.

The 1995 diff is a little longer than the others so if you switch to it you have to shorten your drive shaft or....wait for it...use a 1995 drive shaft.

I will be sourcing a 1995 diff to use for its case and shoving e46 m3 internals inside.

Well, my e38 is a '95. So I'm in luck haha

[Cobrajet429]

Are there higher ratios available?

Holy cow, these things are already geared way to high, which is part of what makes them feel a little sluggish off the line. I'm all for good gas mileage, but how high do you want to go? I'm thinking a lower gear, somewhere around a 3.23 would be about ideal for these cars, giving decent acceleration off the line without being so low as to totally kill highway mileage.

[psjr]

I've been doing a lot of research on this topic and here is what I have put together from the mess of threads out there:

The 1995 E38 is the only year with the normal 210mm "large case" diff. 96 and up cars have a redesign that use 215mm internals. The later diffs you are not going to find gears for aside from the 3.15 sport options. LSD units for the later style 215mm diff are aftermarket units and very pricey. There is no OEM option.

If you obtain a 1995 e38 diff you can swap in the internals from other 210mm large case differentials like an e39 M5 (3.15 lsd), an e46 m3 (3.64 lsd), etc.

The 1995 diff is a little longer than the others so if you switch to it you have to shorten your drive shaft or....wait for it...use a 1995 drive shaft.

I will be sourcing a 1995 diff to use for its case and shoving e46 m3 internals inside.

Thanks for your research, it's something I've always figured could be done one way or another but not high enough priority for me to do all the research.
My main question would be whether the earlier large case diff internals (E32 ?) could fit into the 1995 case.

[007008]

Holy cow, these things are already geared way to high, which is part of what makes them feel a little sluggish off the line. I'm all for good gas mileage, but how high do you want to go? I'm thinking a lower gear, somewhere around a 3.23 would be about ideal for these cars, giving decent acceleration off the line without being so low as to totally kill highway mileage.
I'd be willing to bet he meant a lower gear. Just goofed on the terminology.

[psjr]

High ratio = high number = "short" gear
Low ratio = low number = "tall" gear.

I think everyone is straight on their terminology, but the "high"/"tall" can be confusing to interpret.

[Jamos]

The higher the number the higher the hwy rpm will be.

You will get a more powerful feel off the line with a higher number. 2.95 to 3.64 would be a huge difference in power feeling. Especially keeping an eye open for an e46 gear set for my 95!

[Cobrajet429]

The higher the number the higher the hwy rpm will be.

You will get a more powerful feel off the line with a higher number. 2.95 to 3.64 would be a huge difference in power feeling. Especially keeping an eye open for an e46 gear set for my 95!

Jamos, a 3.64 is a lower gear than a 2.95.

[Jamos]

Higher the number I said! 3.64 is a higher number than 3.15. I was demonstrating/adding to what psjr said! It's why people get confused with the terminology.

Easiest way to remember is that... the lower the number the slower the acceleration and it's purely logical anyway! :)

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... i want more power and don't are about hwy rpm. 2100 to 2600 won't make as much of a difference to mpg as it would to acceleration =)

[Cobrajet429]

Yes, but please let's stick with the correct terminology to avoid confusion.

[Jamos]

Where have I used incorrect terminology!?

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Ooohhh further up. I aplogize. Thanks for making sure it's not mistaken :)

[iDreadnaught]

Think of it as lower/shorter gears spin up faster to the next shift point as opposed to higher/taller gears, and the higher the number, the shorter the time it will spin up to the next shift point.

But I know what you meant. :)

I'd love a 3.45 or 3.46 LSD, but VAC quoted me over 3 grand.

[Jamos]

I'm looking at a lot of sites now too, and I think I want a 3.91 gear ratio.

I've read this on a forum:

"Type 188 cars:
All E36 models, except the 3.2lt M3.
All E30 6cyl models.
All E34 models, except the M5 and 540i.
All E32 6cyl models.

Type 210 cars:
E46 M3 and E36 4door M3.
E34 M5 and 540i.
E32 740i and 750i.
All E38 models.
E39 V8 models, could be all models but not sure.

I see that and figure, I should be able to take gears out of an E32, E34, E46.

I suppose there must be more, but if I find a differential on eBay for $150 why can't I buy that, take the gears out, and toss them in my current diff? (otherwise just throw the whole diff on the car)

TO get back on track with this thread: What is it that's preventing us from doing this? I've done a lot of work with gears on RC cars and helped so many people with transmissions and gears before, but I'm clearly missing something with this here! Again I figure I can just buy a used diff, take the gears out, put them in mine and bolt it back up.

[deathsled]

TO get back on track with this thread: What is it that's preventing us from doing this? I've done a lot of work with gears on RC cars and helped so many people with transmissions and gears before, but I'm clearly missing something with this here! Again I figure I can just buy a used diff, take the gears out, put them in mine and bolt it back up.

Nothing. You have a 95 so you can simply swap internals. Everyone who doesn't have a 95 has to go get a 95 case and do the swap.

You can't throw a non e38 diff on the car. The mount points are unique.

[Jamos]

Nothing as in, "I don't need to change anything I simply take the gears out of one diff, and put them in my diff and I don't need new seals or anything strange?" Or nothing as in, "You can't do anything."

I do get the part about 1995's being lucky enough to have the larger diff.

Since there are a couple of us here with the '95s looking to do this, am I right to believe:

Any "large diff" BMW such as the E32, E34, E46, E83 X3... if we can find a used diff, we're able to swap the parts in? Just a matter of dropping the diff, opening it up, pulling parts, and stuffing the "new" parts in?

[TxDarth]

I'm looking at a lot of sites now too, and I think I want a 3.91 gear ratio.

I've read this on a forum:

"Type 188 cars:
All E36 models, except the 3.2lt M3.
All E30 6cyl models.
All E34 models, except the M5 and 540i.
All E32 6cyl models.

Type 210 cars:
E46 M3 and E36 4door M3.
E34 M5 and 540i.
E32 740i and 750i.
All E38 models.
E39 V8 models, could be all models but not sure.

I see that and figure, I should be able to take gears out of an E32, E34, E46.

I suppose there must be more, but if I find a differential on eBay for $150 why can't I buy that, take the gears out, and toss them in my current diff? (otherwise just throw the whole diff on the car)

TO get back on track with this thread: What is it that's preventing us from doing this? I've done a lot of work with gears on RC cars and helped so many people with transmissions and gears before, but I'm clearly missing something with this here! Again I figure I can just buy a used diff, take the gears out, put them in mine and bolt it back up.

Several things here - 3.90 would be a bitch to drive on the street on a daily basis. Quick off the line but cruse would be too high rpm. The e46 and others you mention have 5 or 6 speed trannies where the final is not 1:1, it will .8 or .9 :1 or like an overdrive in years gone by.

Then it is not just remove and replace - it has to be the right length pinion, then the set up - heal to toe and depth of gear mesh is not easy for the novice to set up. That is one reason it is fairly expensive to have done. I have seen experts that do this daily spend an hour or two setting one up.....

[Jamos]

The math says my current first gear does 40mph. If I did a 3.91 I'd be at 31mph first gear.

25% higher rpm isn't really a concern for me because when I drive 120KM/H I'm at 2200rpm and if I throw it in 4th gear I'm at 2800rpm. I see 8L/100km at 2800rpm and 7.2L/100km at 2200rpm.

I'm not concerned about MPG as per that math... (gotta pay to play!) and I'm always rowing through the gears 1..2..3..4..3..2.3..2..1 while I drive the city anyway. I PERSONALLY don't have an issue with not being able to beat a Bugatti Veyron in a top speed run, but I'd certainly like to know I could take a Civic DX off the line once and awhile. That's just me.

So yes of course it's not just, unbolt the diff, toss some gears in and presto it's done - I would certainly be taking this to my buddies shop and saying, "... here have a go!" But my primary concern is: The diff size is one thing, but I believe all I need to do is change a couple things (ring and pinion) and the rest can stay in there.

I didn't realize you also have to change the drive flange etc...

I guess my primary question still stands: Even though this is a worse ratio than I have now, I thought all I would need is this: http://www.ebay.com/itm/BMW-2-93-Ratio-210mm-Large-Case-Differential-Gearset-Diff-Gears-/171401039751?pt=Motors_Car_Truck_Parts_Accessories&hash=item27e84c4f87&vxp=mtr

So if I found those parts in a 3.91 I assumed that's all I need! =)

Thanks for the help so far

[iDreadnaught]

Driveability would be so sensitive for a street car with gears that short.

It's fairly simple for the '95s. There's a thread that I'm trying to find, I'll post it soon as I find it :)

[Nyc Dito]

back in my E39 days on another board, i had wanted to do the Dinan Diff as my next mod on my M5..never got to do it, but this vid shows how it can pull quicker than the stock diff..

please note, the S2 is obviously modded..but that doesnt take away from the acceleration capabilities when you swap out the diff. Yea, you lose top end, but how often does one travel over 160mph every day (M5's top speed was brought down to around there i think, as opposed to 200mph)

https://www.youtube.com/watch?v=C6euI1m2SKQ

EDIT
You S62 guys should look into the diff upgrade now that i think of it, you'd KILL many many cars off the line...

[Jamos]

I keep seeing on different threads, "For a street car that's going to be crazy!"

I'm missing something else then. It's an automatic! When I'm not on the gas, it will be in over drive. When I'm on the gas, well I'm on the gas! How would having 25% shorter gears drastically change the driveability outside of making the car feel peppier? =)

[Nyc Dito]

I keep seeing on different threads, "For a street car that's going to be crazy!"

I'm missing something else then. It's an automatic! When I'm not on the gas, it will be in over drive. When I'm on the gas, well I'm on the gas! How would having 25% shorter gears drastically change the driveability outside of making the car feel peppier? =)

it basically moves the car quicker. All power has to get to the floor, to the wheels. Regardless of power, you can have a pretty quick jump off the line over another car with different ratio. perfect example for me was when i did this to my AE86. Off the line, id jump on anything i ran against, but would be over powered by higher powered cars eventually. Look at real drag races, look up their specs and they have a ton of power and high gears, made or engineered for 1/4 mile..they just need to get there as fast as possible.

[Jamos]

No I totally get that, and that's why I WANT at least a 3.64 set! I'm still dying to know if ALL I need is a ring and pinion! I can't find a 210mm set anywhere. I saw diff's the other day for $150-200 and figured, "Why don't I just get one of those and take the gears out and put them in mine, it'll be much peppier for only a couple hundred bucks!"

And now I'm finding JUST ring and pinion for $1000!!?

So since I have the 210 case, I'm looking for other cars that had this that had the shorter gears. Then trying to find inventory, but am still not clear on if just the pinion and ring gear are all I need and then Darth messed me up with different flange sizes etc, I don't see how that can be an issue with a simple gear change and not the entire diff!

I'm no diff expert but I believe the ring gear just bolts on to the . . . . ring gear carrier part!

There are so many threads about people wanting LSD setups for their cars, I couldn't care less for open vs lsd as this car is so heavy I don't want it sideways ever anyway! I just want more punch off the line or when passing! Again I figured for a few hundred bucks when it's all said and done, how could I go wrong? I've yet to find out HOW I can go wrong, and yet I've yet to get any solid answers from the 100 threads I've read through covering the past 10 years of all of these cars haha! :D

Does anyone know how I can turn my '95 210 3.15 open diff, in to a 3.91 open diff, for low cost? <-- maybe I should have just said that at the start!! =)

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I'm using this site for the calculations right now:

http://www.advanced-ev.com/Calculators/TireSize/

It's pretty straight forward!

3.15 @ 100mph = ~ 3900rpm
3.91 @ 100mph = ~ 4900rpm

I never go 100mph, too old for that now! So actual cruising speeds for me:

3.15 @ 55mph = ~2150rpm
3.91 @ 55mph = ~2675rpm

As far as acceleration goes VS mpg ...... I think it's a clear win!

[iDreadnaught]

All your '95 needs is the 210mm gear set and you are good to go. As far as which cars came with a 3.91, I have no clue. I know you can get a 3.62 from some E32 750s.

[Jamos]

Thank you, I understand that but I'll try again, what does, "the gear set" consist of? =)

[iDreadnaught]

The ring and pinion.
http://www.ebay.com/itm/BMW-210mm-Large-case-ring-and-pinion-3-46-Ratio-BMW-E23-E32-E34-E38-E39-/191216754165?pt=Motors_Car_Truck_Parts_Accessories&hash=item2c85681df5&vxp=mtr

[Jamos]

Thank you very much.. Ive come across that listing 50 times its been my only hope today!! :D

2 left they say.

SO I AM on the right track!! =)

[iDreadnaught]

Here's the thread I tried to find earlier, it pretty much sums everything up where all the other threads drifted off.
http://forums.bimmerforums.com/forum/showthread.php?1962267-E38-s-and-LSD

Summary on the last page by wanganstyle;


Does it?

I feel the solution is already found in the 95/96 rosetta stone e38 and the e39 m5 units. Installing the matching driveshaft or shortening the existing driveshaft to accommodate the longer m5 diff is the most straightforward solution as it bolts right in.

E39 540i guys are often installing:
E39 m5 lsd unit
E39 m5 driveshaft complete (or rear half only+rebalance if your car is automatic)

Much easier than e46 non m where the only bolt on LSD option includes the entire subframe change over with diff change also to e46m3.

For e38 lsd install:

1995/6 early e38 diff shell
+any 210mm lsd
+any 210mm gearing
+ matching driveshaft or 95/96 m60 e38 rear driveshaft half to make hybrid+balance

Adapting old lsd units to be plug and play to 1996-2001 215k cars is always possible if there is infinite time and free machine work avail to one.

Just like how in lemons racing there is a geo metro with motorbike engine mounted in the rear and chain driven ( by magical $0 billet one off
parts); many dream and talk big but cannot pull together magic when actually trying to get a complete product; BMW is not to be blamed as there are plenty of aftermarket lsd units available to those with the means and desire to have a lsd in a body BMW never fitted one in.

Even if there was a brand new direct fit lsd unit at budget price ($800-1000) for e38/39 v8 non-m cars the number of buyers for e38/e39 use would be very limited: e39 m5 is cheap to buy now (7-10k) and comes with lsd standard.

Sent from my GT-N7100 using Tapatalk 2

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Thank you very much.. Ive come across that listing 50 times its been my only hope today!! :D

2 left they say.

SO I AM on the right track!! =)

Yes sir. You just need the gears, you and your '95. I'm not jealous at all... :(








LoL :D

[blackknight530i]

You S62 guys should look into the diff upgrade now that i think of it, you'd KILL many many cars off the line...

Trevor already has the M5's 3.15 LSD in his and I plan on doing the same. I just purchased a 750il rear subframe with rear sway bar to go under the knife like Trevor's so I can eventually mount one. It will be getting new bushings and hopefully relocated rear diff mounts. Theoretically, I could then mount any E39 diff I wanted to, even an open 3.46, without changing the driveshaft (This is another discussion that I'm still rattling around in my brain and will post about separately).

[Cobrajet429]

I keep seeing on different threads, "For a street car that's going to be crazy!" I'm missing something else then. It's an automatic! When I'm not on the gas, it will be in over drive. When I'm on the gas, well I'm on the gas! How would having 25% shorter gears drastically change the driveability outside of making the car feel peppier? =) Mainly because at interstate speeds(70 mph), you would be turning such high revs. I don't know what overdrive ratio is in these, but I'm assuming around .7:1. The lowest gear I've been happy with for a daily driver was a 3.73. I notice that you mentioned 55 mph, if that is the interstate speed limit where you live, I'd be ok with 4.11a

BTW, thanks a lot Nader, at least most of the country had enough sense to raise it back to 70.

[Jamos]

Here its probably 60. The major hwys are 100kmh but everyone does 130 anyway. It's why they won't raise it.

3.73 or 3.91 is a definite go.. I just can't find them :)

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I seem to think....... having a '95 is A CURSE! I can't find ANY ring and pinion s except for that ONE posted above @ $300 for a 210case. EVERYTHING I'm finding is 188mm and costs $50-150! Nothing for mine :(

[iDreadnaught]

http://www.ebay.com/itm/BMW-E31-E36-E46-LIMITED-SLIP-DIFFERENTIAL-LSD-3-64-LSD-M3-840CI-850CI-M5-540-/231297360831?pt=Motors_Car_Truck_Parts_Accessories&hash=item35da65a3bf&vxp=mtr

Closest that I've found.

If only I could swap internals and have a 3.64 LSD for $1200... :(

[Jamos]

You think $1200 is a good deal? I don't get it, why are there ring and pinions for 100 different 188 boxes, and none for the 210? I have to pay $1200 for that diff so I can do what others do for $150 and yet you say I'm the lucky one?? I swear to god I'm missing SOMETHING KEY here. haha! =D

[iDreadnaught]

Check these guys out, they sell 3.91 must be rare as reflected in the price
http://diffsonline.com/new-motorsport-210mm-3.91-ratio-ring-and-pinion-with-14mm-bolt-holes.html#.U-rKlmP7Qug

[Jamos]

I've clicked that link 100 times today, diffsonline.com refused to load. But again $1100!? EUGH........ this dream is quickly coming to an end. Besides that setup is for the M14's which I think I only have 12, so I'd need an additional $50 in hardware :D At $1100 doesn't sound like much, but when I thought I could buy a $150 used differential, pull out a couple gears and call it a day, this isn't so much an option anymore!

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Then there's the 12mm version of the 3.64 which would be doable.

http://diffsonline.com/used-210mm-3.64-ratio-ring-and-pinion-with-12mm-bolt-holes.html#.U-rLt_ldV8E

Cost $100 more than the 14mm version!! Hahah

[iDreadnaught]

You think $1200 is a good deal? I don't get it, why are there ring and pinions for 100 different 188 boxes, and none for the 210? I have to pay $1200 for that diff so I can do what others do for $150 and yet you say I'm the lucky one?? I swear to god I'm missing SOMETHING KEY here. haha! =D

Well for an LSD it's a good deal to me, VAC quoted me close to 4 grand for a 3.64 LSD.

If switching gears so short that breaking traction would be easy as pie, I'd rather have an LSD to get power to both wheels instead of spinning the one wheel with the least traction.

DSC's "easter egg mode" would help but, it's not the same feeling.

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I've clicked that link 100 times today, diffsonline.com refused to load. But again $1100!? EUGH........ this dream is quickly coming to an end. Besides that setup is for the M14's which I think I only have 12, so I'd need an additional $50 in hardware :D At $1100 doesn't sound like much, but when I thought I could buy a $150 used differential, pull out a couple gears and call it a day, this isn't so much an option anymore!

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Then there's the 12mm version of the 3.64 which would be doable.

http://diffsonline.com/used-210mm-3.64-ratio-ring-and-pinion-with-12mm-bolt-holes.html#.U-rLt_ldV8E

Cost $100 more than the 14mm version!! Hahah

Well I hope you can find one reasonably priced, I'd be tuned in for the swap for sure

[Jamos]

Yeah I agree an LSD is a sexier option! But I just know I'd let myself burn rubber all day if I went that route, and then in no time I'd need new suspension parts, driveline parts, and yuck not again! Did that and got it out of my system with the SRT8 years ago :D

Ah well, I've made a few posts on a few forums today all with EMAIL NOTIFICATION so hopefully someone will bite and say, "no no just find a ______ at a wrecker, it has the shorter gears and will transfer right over to yours no problem!" But so far my only option is the M5 from way back annnd I don't see any availability there - people who still have them bought them or trashed them I assume =D

[deathsled]

I don't think you're going to find 3.91 out of another car unless it was upgraded. 3.91 gears in the 210mm size are a racing/motorsports part. It's possible they aren't even an OEM item.

Internals swap from an e46 M3 is going to be pretty much the cheapest way to get a shorter gear than 3.15 under $1000 AND you happen to get an LSD with it (though viscous and not clutch type).

[Jamos]

Okay thank you again. I was under the impression that all kinds of cars came with them back in the day! :)

[deathsled]

Okay thank you again. I was under the impression that all kinds of cars came with them back in the day! :)

Well sure, gear sets in that ratio have been available for all sorts of cars for 50+ years I'm sure, but only ones designed for a large case BMW diff are going to fit.

You aren't going to stuff a 3.91 from a Ford 9 inch rear in there.

[Cobrajet429]

Okay thank you again. I was under the impression that all kinds of cars came with them back in the day! :)

I've never heard of a BMW with a DragPak option.

[Nyc Dito]

You aren't going to stuff a 3.91 from a Ford 9 inch rear in there.
SOUNDS LIKE A CHALLENGE! lol

[Jamos]

No I meant there are plenty of forums from 2003+ with people talking about putting 3.64, 3.73, 3.91 gears in their 210mm diffs. They mention E32, E34, E46, E60, X3, etc all use the big case and all have gears that would fit. Yet when I look I can't find anything except the smaller 188 "medium" case gears.

[deathsled]

X3 uses the medium case from everything I've seen. I think there's a lot of misinformation and here-say out there.

You can get a 3.91 for the large case from Turner Motorsports. It's $700. From what I can tell 3.91 (as well as 4.10) was never a factory supplied large case gear set. It's aftermarket.

I think the only OEM options for 210mm ring and pinion sets are 2.93, 3.15, 3.46(?), and 3.64.

Oh I'm wrong, E34 M5 is the 210mm 3.91 it looks like.

[Jamos]

You see that's been my problem. I'd see one thing and then the opposite.

the 34 m5 did come with 3.91 for sure though it's why it's a direct swap for the 95 :)

3.64 would be worth it if I could only find it but I can't. The rest aren't worth it imo.

thanks for the info and checking too! :)

[deathsled]

3.64 would be worth it if I could only find it but I can't. The rest aren't worth it imo.

thanks for the info and checking too! :)

You can find 3.64 in any e46 m3 differential. They're like $400-500 all day long on eBay AND you get an LSD with it.

[Jamos]

And I don't need new flanges or anything? I understand the internals but not how it mates up to the car or anything. The viscous led it comes with. .. does it ever need service?

[deathsled]

If your existing diff to axle stubs/flanges don't fit then I believe you need to switch out to E39 M5 ones.

The front input shaft/flange would be reused from your own diff.

LSD and gears for an e38 is way more complex than it needs to be...lol

[Nyc Dito]

some info from the past...

http://forums.bimmerforums.com/forum/showthread.php?1962267-E38-s-and-LSD&highlight=e34+diff

[Jamos]

Thanks for that link, I was trying to find it the other day! I had read through it months ago and it's what gave me the confidence that this could all be done in the first place.

I'm curious, what's NEEDED to do this?

From what I understand all I need to look out for is the 14mm ring gear bolts, vs the 12mm ring gear bolts that I would have in my '95 as it's NOT an M car. Apparently the M car's bolt the ring gear using 14mm bolts instead of 12mm.

SO find a gear set that is 12mm bolts, that fits a 210mm box and I should be fine!

How does the pinion mate up to the drive shaft, will it always be the same so long as it came from a 210mm box?

Also, what else is needed?

Crush washer, bearings.. does the pinion usually COME with bearings?

If I ordered a ring and pinion 3.64:1 from this person tha tjust emailed me for $275, what else will I need in order to make a proper install?

Trying to be as direct as possible to keep as it as understandable as possible! =)

[blackknight530i]

I thought the 14mm vs 12mm bolts were for the axles, not the ring gear. I think it was for determining the correct output flanges. I could be wrong though, just a foggy memory.

[Jamos]

Sites that sell JUST the ring and pinion mention two sizes. For instance:

http://diffsonline.com/new-motorsport-210mm-3.73-ratio-ring-and-pinion-with-12mm-bolt-holes.html#.U-1bCPldV8E

That site explains:

"When installing where a ring gear with 14mm ring gear bolts was, order a set of 12mm bolts and the 14mm to 12mm spacers to ensure proper operation."

=)

[blackknight530i]

Hmm, ok.

[purplecty]

I replaced the diff in my 750iL with a 3.15 model from a 740i Sport. Paid $200, did the install myself. Nice upgrade from stock.Researching the 3.15 diff upgrade for a friends 2000(3.99 build) 750iL. I see a difference in the sport diffs showing a 102mm and a 94mm axle flange length. Anyone know the build dates between the 2 lengths or what the difference is?