LSD Rebuild Info

[brickwhite]

I posted this on someones LSD inquiry. I thought I would put it here too. These are other sites were they have rebuilt a LSD.

I know you can buy a used one for about $250-$350 but if you want to tackle a rebuild and don't want to pay Metric Mechanic or Diffs Online $1200 to do it. Here you go.



You can still buy all of the bearings, clutch plates, and seals for the medium case diff.

Rmeuropean.com has the parts listed for pretty good prices.

ie - bearing is $21

http://www.rmeuropean.com/Part-Number/C ... 21741.aspx



Your local dealer can also get them for big bucks. If you look them up on realoem.com make sure you look them up for a 87 e24 (635i) they part the diff better on that car for some reason.

http://www.realoem.com/bmw/showparts.do ... g=33&fg=15



Pretty sure medium case has 188mm internals which are the same on alot including the e36


Hear are some sites for diff rebuilds DIYs:


http://www.ohiobimmers.com/forum/showthread.php?t=3624 The Best one , but you have to login

Pretty Good tear down and rebuild: (check out this M3 rebuild, AMAZING!!)

http://www.r3vlimited.com/board/showpos ... stcount=44

http://www.r3vlimited.com/board/showpos ... stcount=45

http://www.r3vlimited.com/board/showpos ... stcount=46

http://www.r3vlimited.com/board/showthread.php?t=92714

http://www.m3forum.net/m3forum/showthread.php?t=362856

http://forums.bimmerforums.com/forum/sh ... ?t=1650106

Here are some important specs for E36 188mm differentials (others similar):

Ring and Pinion Backlash = 0.06mm to 0.14mm (0.0024in to 0.0055in - Metric Mechanic believes ideal backlash is 0.003in to 0.0035in, which falls well within the BMW TIS limits)
Pinion Preload = ~12in-lbs to 23in-lbs according to TIS (Metric Mechanic claims 14in-lbs to 16in-lbs)
Carrier Preload = ~11in-lbs to 23in-lbs according to TIS (Metric Mechanic claims 9in-lbs to 11in-lbs)
Axle Cap Bolts = 10ft-lbs + 40 degrees angle torque (with Loctite 242)
Rear Cover Bolts = 34ft-lbs
Limited Slip Carrier Cover Bolts = 25ft-lbs
Ring Gear Bolts = 110ft-lbs (with Loctite 271)

Part Numbers:
**Asterik denotes a non-BMW part number. It is specific to the part in general, but not brand, e.g. Timken HM88542 or SKF HM88542. Once you have the bearing and race part numbers, the sky is the limit. I refuse to pay $73 per bearing through the stealership for an SKF bearing, the same one I can find for $22 with the generic number.

**HM88510 Pinion Race x1 **
**HM88542 Pinion Bearing x1 **
**LM503310 Carrier Race x2 **
**LM503349A Carrier Bearing x2 **
**HM89410 Pinion Race x1 **
**HM89449 Pinion Bearing x1 **
33107505602 Axle Shaft Seal x2
33111214144 Axle Cap O-Ring x2
33139065734 or 33139065735 Shim Sets for Carrier
33101214099 Pinion Shaft Seal x1
33121744368 Pinion Crush Sleeve x? (Depends how experienced you are. If you've done it before, you can suffice with one. If not, I'd have at least two on hand.)
33129065179 or 33129065180 Shim Sets for Pinion
23211490120 Securing Plate for Pinion Nut x1
33121200258 Pinion Collar Nut x1

Brands for roller bearings and races:
Timken
SKF
FAG
National
BCA
Fafnir
Koyo

Tools Needed:
Shop press
Race/Seal driver kit
Dial indicator with clamp or magnetic base
MAPP gas torch
Small cut-off wheel (air powered)
Bearing puller
Metric sockets up to 30mm
Ratchet
Impact
Assortment of screwdrivers
A few punches and chisels
Hammer
Large brass drift

I'm putting this out here as a feeler so that more people have an understanding of what goes into building a diff, and that IT IS POSSIBLE TO BUILD ONE
_________________

[tsmall07]

Thanks for putting the work into getting all that info. We've already got a Tech FAQ for clutch replacement here. It should be noted that replacement of bearings in the diff is not worth the work if yours are not currently making noise. If the oil level is kept up in the diff and changed every 5 years or so, the diff bearings can last forever.

I just purchased a set of LSD clutches for my diff from Bimmerworld and will be completing this repair soon. In college, I installed lockers in diffs and set up a set of gears or two, so I don't expect to have any issues.

[Cupholder Zealot]

I just made contact with the guy at Precision Gearing, which used to be the company Metrix, who put out upgraded diff kits. It appears that they still provide those parts and services for our diffs. His name is Rob and he is at:

ronin at precision(nospace)gearing dot com

Not sure what I'm going to do about my diff. I figure if I put it in front, I wouldn't want to rebuild it anyway

[Frybrid 524td]

You shouldn't list Rob's email address outright. Bots will spam him to hell.

[Jeremy]

You shouldn't list Rob's email address outright. Bots will spam him to hell.

That should make it difficult enough for the bots to decipher.

[Cupholder Zealot]

Gotcha,

Thanks for the heads up.

[M535]

Machining the ramp angles will make a huge difference to the locking performance of the diff, this is very easily done on the ZF typ 188, we have done this on LSD rebuild/upgrades in conjunction with adding extra plates with great results.

Another tip is to use a non-LSD rated oil if you require better lock-up as the oil is less slippy. This is totally fine to use and will not damage your diff or cause your diff to "blow up"!

Oil-wise, BMW diffs tend to run hot so a decent fully synthetic oil such as Redline 75W140 is good practice. This is also available in a less-slippy option for better locking - 75W140NS.

Hope this helps.

[demetk]

Please explain ramp angles. Having matching ramps to get the car in the air is the only thing that comes to mind.

[Cupholder Zealot]

Most of the time when I am thinking about ramps, I'm hungry.



http://www.time.com/time/nation/article ... 46,00.html

Not sure of my own angle on these, but most things get better with a little heat.

[mooseheadm5]

I'll explain more later but ramp angle has to do with onset of lockup and the resulting pressure on the clutch plates from differential wheel speeds.

[Jeremy]

I'll explain more later but ramp angle has to do with onset of lockup and the resulting pressure on the clutch plates from differential wheel speeds.

I'm familiar (loosely) with what ramp angles are, but I don't know mechanically how they're accomplished or how they would be modified. Is this something that you'd really need someone with special machine tools to do for you?

[mooseheadm5]

I'll explain more later but ramp angle has to do with onset of lockup and the resulting pressure on the clutch plates from differential wheel speeds.

I'm familiar (loosely) with what ramp angles are, but I don't know mechanically how they're accomplished or how they would be modified. Is this something that you'd really need someone with special machine tools to do for you?

Whether or not you can mod ramp angles by hand depends on how the diff is designed. I have never had a BMW diff apart, so I don't know if you can do it on one of these.

[Rich Euro M5]

The key to rebuilding these diffs is having the correct tools to set the bearing preload. BMW differentials utilize a crush sleeve for pinion bearing preload, and shim stack for the carrier bearing preload. There is also a pinion shim which sets the ring / pinion gear lash.. The procedures at the links are OK for rebuild, but do not go into setting up the differential with a new ring / pinion gear set. If you wish to change the ratio by replacing the ring / pinion gears, additional tooling is required measure the thickness of shims required to set the pinion depth.

FWIW:The link at Bimmerworld is the best one.