Diff replacement guide M140

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Mbateman
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Diff replacement guide M140

Post by Mbateman »

Anyone got a guide to swapping the diff on a 140?
I just want to make sure I’m prepared before starting.

I know I need the 50mm prop but spanner.

I assume:
Car up on lift.
Exhaust off.
Drain old diff.
Pop shafts out.
Any suspension need undoing to get shafts out of the diff??

Cheers
Matt


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mick.86uk
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Re: Diff replacement guide M140

Post by mick.86uk »

You'll need to remove the rear suspension/control arms on one side at the hub so you have enough movement to pull the drive shaft out from the diff.

See vid below:
https://www.youtube.com/watch?v=-1SAuMlu_Tk
Last edited by mick.86uk on Tue Mar 12, 2019 3:53 pm, edited 1 time in total.
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marco_polo
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Re: Diff replacement guide M140

Post by marco_polo »

No need to remove the exhaust, but you do need to remove most of the suspension from one side of the car (to remove one driveshaft), as Mick says.

It was so much easier on the E Series cars. :(
Current: Silver F21 M135i - ManBox - HK - Adaptive + Eibach Pro's - BBS CH-R's - BMWP Drexler LSD - M4 LCA's

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Mbateman
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Re: Diff replacement guide M140

Post by Mbateman »

Cheers guys

So I’ll also need geometry checking/adjusting after?

Matt


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Re: Diff replacement guide M140

Post by marco_polo »

Yes. I put mine back together the same as it came apart (as accurately as I could) and it was quite a way out on that side.
Current: Silver F21 M135i - ManBox - HK - Adaptive + Eibach Pro's - BBS CH-R's - BMWP Drexler LSD - M4 LCA's

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Mbateman
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Re: Diff replacement guide M140

Post by Mbateman »

marco_polo wrote:Yes. I put mine back together the same as it came apart (as accurately as I could) and it was quite a way out on that side.
Just been doing some more research.
According to the BMW procedure, here > https://www.2addicts.com/forums/attachm ... 1483322235
And this photo I found on birds web site Image
It should be possible to drop the diff out without disconnecting any suspension arms?? Do you think that right/possible?


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Re: Diff replacement guide M140

Post by marco_polo »

Looks that way, if you have a ramp and a transmission jack.
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Mrbarry
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Re: Diff replacement guide M140

Post by Mrbarry »

Late to the party on this thread but I have just fitted a LSD to my M140 without removing the wheels or suspension.
I followed the link Mbateman posted and it’s an easy enough job.
My findings:

Remove the under body prop catcher plate, 6 T30 bolts.

Exhaust is very easy to get off, but it’s easier with 2 people. 4 nuts and it’s off. 13mm socket. Oh, remember to unplug the exhaust valve cable.

Next undo the 50mm nut on the diff to prop, it’s tight but I used a large spanner with a 1meter scaffold pole, it comes loose with very little real grief. Check direction of rotation before you start, it’s a right hand thread but turns differently to how you think, you’re screwing or off the prop not out of the diff!

Get a transmission jack under the diff. Forget it if you don’t have one. I’m not saying you could not do it but it would be crazy!! It’s HEAVY to hold over your head.

Start to remove the two front diff mount bolts, 19mm socket, but leave them in a couple of turns.

Use 2 21mm sockets and remove the rear diff mount bolt nut but leave the bolt thru the casing.

Now the diff is almost free. Get a lever bar with a good clean flat end, not some chewed up old thing, and locate it in the slot on one drive shaft close to the diff body, I used a socket as a spacer to rest the fulcrum against so I got good leverage, pop the drive shaft out about 10mm, it comes easily enough but expect 2 or 3 attempts.

Fully remove the three diff bolts now and lower it down a few inches. This lets you slide the prop shaft fully out and use a bungee cord to hold it up out of the way. You will now be able to very easily angle and turn the diff to withdraw the first drive shaft and cable tie that up out of the way.

Re-fit the three diff bolts to hold it steady, don’t bother putting the nut on the rear bolt, only go 4 or 5 turns on the front ones. This holds the diff solid so you can pop the second shaft out 10mm.

Remove the three bolts again and the diff comes off real easy.

Clean the thread on the end of the prop shaft with a wire brush.

Refitting is easier, change the locating clips on the drive shafts, new diff onto the jack, get it up and slide the shafts in one at a time but they won’t fully lock at this stage. ****Note the seal protection rings these are very important. Most important part of the job perhaps. They are supplied by Regalautosport but not sure about other companies. BMW sell them if you don’t have any. They open up like a ring pull so that one half stays in the seal and the other half hangs down to get your finger thru, you slide the shaft into the diff 70% or so, then stick your finger in the loop hanging down and slide the whole thing out of the seal then snatch it hard off the shaft, the inner part snaps at a pre determined weak point and it comes away cleanly. This prevents any chance of damaging the seal during installation. It’s an excellent system. ****

Once both drive shafts are in get the prop shaft in to the diff but don’t do up the nut yet.

Get the diff jacked up and replace all 3 mounting bolts. Torque them up.

Apply thread lock to the 50 mm prop nut thread and thread it back on, torque it up.

Use a rubber mallet and gently tap the drive shafts until they click in. They go easy.

Remove the diff oil inspection plug and fill it with oil until it starts to run out. Put the plug back in and torque it up.

Replace the exhaust and prop plate and you’re finished.
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Simon Site Manager
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Re: Diff replacement guide M140

Post by Simon Site Manager »

I had an MP LSD fitted in January this year (Williams Performance), was reading the web and someone mentioned that you should change the diff oil after a month. I duly pannicked and changed the oil last month (October). It was a lot easier to get out. than put new stuff in; it was filthy black and had lost loads of viscocity. I sleep better now!
'17 M140i Estoril Blue Most of the toys. Every time I see an F40 it makes me :(
Mrbarry
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Re: Diff replacement guide M140

Post by Mrbarry »

I asked the same question of Regal who said they never change it in wavetrac but would consider it in a M performance or other plate diff. Well I specifically asked if it was worth checking the level after a week or two in case any oil settles in webbings in the casting as I have not opened one to know what’s inside but the conversation led to oil changes.
I don’t think anyone can argue that new oil is better than old however.
Autosri
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Re: Diff replacement guide M140

Post by Autosri »

The wavetrac is a helical diff with a tiny clutch pack so not much friction material to wear where the m performance clutch diff will wear a lot in the first few hundred miles as it beds in but after that it won’t wear down much
Mrbarry
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Re: Diff replacement guide M140

Post by Mrbarry »

Exactly that.
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