M5 limited slip differential transplant into 540i/6 - The Unofficial BMW M5 Messageboard (m5board.com)

DZeckhausen · 11th May 2002, 00:32

A couple days ago, I drove up to NY to pick up a slightly used M5 differential, driveshaft, and halfshafts from a fellow Roadfly member who had just taken them out of his 540i. His lease was up and he has an M5 on order.

The trip itself was wonderful and you can read my review if you like.

That's me on the left. ChrisNY on the right

Here's a few questions for the pros out there who may have done this already. I'll be putting this baby in my car on Monday. After realizing that I wasn't going to be able to bench press this VERY heavy differential while lying on my creeper in my garage, I enlisted the help of Ben Liaw at Rogue Engineering who has a lift.

Along with the M5 diff, the driveshaft, and two halfshafts, ChrisNY gave me some hardware:

The two large nuts look like they are the sort of thing that BMW would advise you to use only once. The crescent shaped objects have some impression left in them from the Torx bolts, and I'm wondering if they are also supposed to be replaced or if I can re-use them. And finally, the Torx bolts themselves. What's the deal? Use once and throw away? Or can I use them again?

If any of these items need to be replaced, can someone give me part numbers?

Next question: What is the capacity of the M5 diff and what fluid does it require? I'm assuming, since the M5 diff uses clutch plates, that there is a requirement to add some sort of friction modifier to whatever gear lube is supposed to go in the case. Is this right? Again, any part numbers or generic specifications?

Thanks, in advance, for your help!

Diamond Dave · 11th May 2002, 01:32

Dave,

I helped my tech with the Dinan 3.45 gear upgrade and can assist on a few points. Again, on the M5 we had to remove the exhaust system from the cats up front, all the way to the back. Needed the room to get to the diff.

I can't speak to those nuts but I would get fresh ones if I were you. For the torx bolts, we did re-use those. No problem. Understand that those puppies get tightened up big time! Have no ft/lb to share but be aware that you want to use some muscle.

Have no idea as to the capacity of the diff fluid as they rolled over a large barrel of heavyweight differential oil. There are two circular plugs that screw into the diff with a large allen wrench. The lower one is used to drain the diff. The one up above is where you pour in the new fluid. My tech kept adding fluid until it started to overflow. It's full!

Hope this helps somethat. Good luck and have a nice weekend. Will do my homework assignment for you tomorrow!

DWP

tfung · 11th May 2002, 11:51

very interesting.... I can see why you would want to change the LSD, but why the driveshaft as well? Is the M5 driveshaft beefier than the 540 one?

DZeckhausen · 11th May 2002, 14:37

Quote:

Originally posted by tfung
very interesting.... I can see why you would want to change the LSD, but why the driveshaft as well? Is the M5 driveshaft beefier than the 540 one?

I think it might be, but that's not the reason for installing it. The M5 diff has different dimensions than the 540i diff. Thus, it is a requirement to replace driveshaft and halfshafts in order to fit this into a 540i.

rvacha · 11th May 2002, 17:58

Hi DZ-
According to TIS...

"front threads" - 150Nm
"rear threads" - 105Nm

Torque specs are apparently the same regardless of the final drive unit used (540 vs. M5)

Fluid is a synthetic with no defined properties, just a type and part number.

Type - SAF-XJ
83 22 1 467 993 (one liter size)

BMW dealers may also have ample stock of SAF-XLS, also a synthetic, but this cannot be used in multi-plate LSDs such as that found on the M5

Hope this helps!

P.S. Please charge the digicam batteries!

rvacha · 11th May 2002, 18:01

One clarification - no additional additive is needed when using the SAF-XJ fluid - just pour it in

Chris Foote · 11th May 2002, 18:09

Hi Dave!

I can't help you with specifics -- I can only comment on what a cool project you have

I would love to see a post about your installation and see what you think of the results!

I have to come down for one of those Zeckhausen clinics this summer (along with some beer!)

Would love to meet you and the crew.

Take Care

-Chris

DZeckhausen · 11th May 2002, 21:08

Quote:

Originally posted by rvacha
P.S. Please charge the digicam batteries!

Thanks for the reminder! They are in the charger now!

Someone on the Roadfly board who has done this modification before (and I respect technically) has told me I should use Redline 75W90 gear oil. I'll try to find some Monday morning. Failing that, I'll get some SAF-XJ at the local dealer or an auto parts store.

540is · 14th May 2002, 14:49

Did everything work out with the diffential transplant??
I cant make up my mind if i should go for a Quaife lsd or swap to the M5 unit for that nice 3.15 (2.81) gearing.