Wavetrac diff and axles question

[Ballard540]

OK questions have come about ALOT

My friend has just bought a 4.10 open diff to go in his 540, he also wants to run a wavetrac unit and has found an M5 rear drivetrain assembly CHEAP axles, control arms, brakes, sensors all of it.

So what needs to be done to make the M5 axles mount up to the other flanges. Now the 4.10 diff obviously came from a 528 or such BUT I want to know what I can do, Can I use the "knubs" or entire flange piece from an M5 and slid into the 4.10 with the wavetrac then the axles bolt right up, or do I need to seperate the axlesd and run a different flange.

Any insight is greatly appreciated. Just fyi car looks to put down 750hp+ at the wheels so I need it to stay in there. Thank you guys!

[Justin517]

cant bolt M5 axles up to an I6 small case... M5 axles/flanges are bigger than 540i which are bigger than 525/528/530... just wont happen. To run the smaller i6 diff in his 540 (not sure why he would do that) he would have to go to the smaller i6 axles (unless there is a flange out there that I don't know about. You would also need a different drive shaft, likely custom.

Also, I don't think the M5 rear subframe is worth the swap, the subframe itself is the same and the brake upgrade can just be bolted onto what he has in the car.

another also... 4.10 in a 540 will suck. I went from 2.81:1 to 3.15:1 and I wouldn't want any lower (numerically higher) gearing than that for something I drive on the street, I'm at about 2700 RPM at 80 MPH... he will be a full thousand RPM higher at 80 MPH... 3700 is screaming for a V8... the car will also top out at about 140 MPH (6500 RPM in 6th) which is 15mph sooner than the electronic limiter.

Lastly... a wavetrac for the 4.10 small case will not come even close to fitting into an M5 case.

All said and done... this whole idea is a cobbled together bad one that will not work and even if you spent the massive amount of time and money to make it work, you would end up with weaker axles and diff, useless first and 2nd gear, screaming at high RPMs on the highway.

I reccomend doing the tried and true M5 3.15 LSD swap, maybe upgrade to a 3.46 at some point after that if you wnat, but I think he would be happy with 3.15.

[topaz540i]

Looks like your best bet is sell your m5 rear to me.

[Ballard540]

I do not have an M5 rear we were looking to buy one for axles cause the 540 axles are very small. I run a blown M62 putting 627 whp and the axles do great so we were gonna use this for his. The car is HEAVILY modified.

It has a 6.0 LS2 fully built running a p600b at 10 psi then a 825 shot. We are running slicks mostly and using this on the track.

He bought a diff with a 4.10 for an e39 and we want to make this work to keep from having to buy a gear set that is 1200.

So I have not bought axles, I want to make the diff work with the M5 axles whatever has to be done. He bought the diff for 98 dollars so this is WAY cheaper. and has to be some way to make it work.

Thing is we NEED a 3.96 to a 4.10 to get the times right so this is the cheapest way to go.

[Jesus Freak]

The small case 4.10 will explode. I asked performance gearing if I could run my 4.10 in my ls3 swap that only puts down 427 whp and he said no way. I had to buy an M diff and axels then had it re-geared. That's your best option IMO.

[wanganstyle]

He bought a diff with a 4.10 for an e39 and we want to make this work to keep from having to buy a gear set that is 1200.


Tell your friend to sell the 4.10 open diff. It is useless for your power level -esp. with an open - even if you welded it together it wouldn't hold more than a few passes - the e39 I6 has a compact drive front pinion.

An aftermarket LSD unit to plug and play to the I6 diff would cost too much.....there is no OEM bmw I6 e39 LSD.

fitting an aftermarket I6 diff is ...more than going full biggie sized e39 M5 complete rear crossmember w/ everything attached.

You can go 3.91 in a 210mm M5 size if desired, that is very close to your target 4.10. Run shorter tires or smaller rims! 4.10 is an aftermarket gear ratio, 3.91 is an OEM bmw ratio avail that can be fitted perfect in a E39M5 case with clutch type LSD.

[Justin517]

yup... small case is not a good idea with huge power, never mind the need to use smaller axles and needing a custom drive shaft.

as mentioned a re-geared M5 diff is probably your cheapest option, but it wont be a wavetrac... it'll be a clutch type. you can add a 3rd clutch with a little machining though and get some serious lockup if you wanted.

It wont be cheap... but you have to pay to play. Spending big $$ on a fully built 6.0, then even more on a blower, then even more still on a nitrous system... then trying to get away cheap on the part that sends the power to the wheels is pretty dumb...

[514mach1]

If budget is a big concern, I vote for a 31 spline 9" ford with detroit locker.

[Ballard540]

Well we just thought it would be the same as the case he ordered said 4.10 210mm so i assumed it was a big case? But maybe that's what I get for assuming.

I run a 3.15 in mine but only make 750 at the flywheel he is looking at that at the wheels and is making a track car. But the 3.91 wouldnt be far off either.

We just checked and it is a 210mm so big case. I guess we will measure when it gets here. We ran a wavetrac before and loved it so his mind is set on it. But I am open to options from you guys!

[514mach1]

4.10 big case does sound odd. But if that's what you've got then that's cool. I'm interested to see what you find when you open it (if it actually is a 210mm ring gear, actually 4.10 ratio, any other details).

[Justin517]

I don't know of any 210mm cases that came with 4.10 gearing, especially with an open diff.

I doubt someone went through the effort/cost of installing a $1000 gear set in an open diff, I even further doubt someone would sell it for $98.

4.10 is available for the big diffs though:
http://store.vacmotorsports.com/bmw-motorsport---210-size-ring-and-pinion-gear-sets-e46-m3-etc-p2196.aspx

[wanganstyle]

OEM BMW 210mm big case ring and pinion in 4.10 ratio does not exist. This is why the e46M3 guys are paying close to $1k for a custom 4.10 ring and pinion.

the 4.10 junkyard lied to you. M5 e39 LSD units only come in 3.15 ratio and are only compatible with select ring and pinion sets.

If there were 4.10mm 210mm LSD compatible ring and pinions from the factory they would be bought out by the e46M3 / z4M3 S54 engine track guys.