Differential Equations

[tig]

Ok, as is usual, after I am stumped and post a message a solution comes to me.

I have a brass block and a sledge hammer. Set the brass block on the end of the pinion and a whack with the sledge hammer and the pinion popped out.

Now I have everything disassembled. From the rusty donor, all the important matching parts:

• Pinion
• Pinion bearings with matching races
• Pinion spacer washer (specific to each pinion & ring gear set)
• Pumpkin
• Side covers (from one of the better cases)
• Side cover shims from the rusty donor, marked for correct sides; match the pinion/pumpkin
• Cleaned cover
• Good case, to be cleaned & painted (also removed races from it)

Now I know precisely what to order:

• Securing plate
• Pinion shaft seal
• Pinon crush sleeve
• 2x output flange seals

I won't bother ordering any side cover spacers because (a) supposedly the ones I have will 'just work' because they are matched to the pumpkin and (b) I have 2 other donor sets that are all different sizes. When I reassemble, if I discover that lash can get set correctly with these spacers, I'll order other sizes.

I'm learning a ton. I hope you, dear reader, are too.

I'm also going to ensure all the fastners on the pumpkin are torqued correctly... maybe I'll pull them and put locktite on? Should I?

[Shawn D.]

Yikes. That ain't no good!

[Jelmer538i]

If your here, also order some new LSD parts:

http://thayermotorsports.com/collections/all

And make sure you check this:

[Mike W.]

I like this thread. Much like auto transmissions which aren't really all that difficult to work on, popular belief is that you need thousands of dollars worth of tools and diffs are impossible to set up correctly. Maybe, maybe not, I worked on a couple back in my air cooled VW days and both came out ok. Didn't put enough miles on them for a long term view, but short term at least they were fine.

[tig]

Painted the case today.

[geordi]

I am digging this thread. Nice work & thanks CEK

[tig]

I am digging this thread. Nice work & thanks CEK

Me too! Thanks.

Spent some time in-between tearing apart the parts car on prep. Cleaned up bare metal and the races are ready to be put in the freezer tonight.



I can't really do anything more but put the races in until the new seals arrive from Blunt sometime this week...

[Jelmer538i]

Are you going to rebuild the limited slip part to? That's really easy now.

[tig]

Are you going to rebuild the limited slip part to? That's really easy now.

Nah, I really don't think it needs it. I could be wrong.

[Jelmer538i]

http://thayermotorsports.com/products/b ... efresh-kit
For this kind of money I would refresh it...

[tn535i]

Those LSD discs at Thayer were very expensive. If the condition looks good I would re-use them.

[Jelmer538i]

$214,99 is not expensive for 2 clutches, 2 dog rings and a bolt set.

I payed $190,- for my 210 diff refresh kit in the UK.

[wkohler]

Hell, I'd add the third clutch. 40% lockup.

[Coldswede]

40% lockup would be fantastic on the Autocross course! It is on my To-Do list.

[foolish]

I'm no diff expert by any measure but after discussing a similar rebuild with Wanganstyle (one of the resident diff experts on R3V) he suggested a stock 2 clutch rebuild for a daily driver as opposed to a dedicated auto x or track car. He has provided a lot of info on diff rebuilding and is worth speaking with.

[tig]

I got my seals and crush bushings from Blunt and got going today. Stymied:



I was able to get the pinon nut off by using a pry bar thorough a hole in the flange, wedged against the case, using the impact hammer.

However, the diameter of the flange holes are such that not even the hardest-steel drift I have is strong enough to withstand the torque required to crush the crush bushing.

I'm now in search of someone who has the special BMW tool designed for this. I have not been able to find any pictures of it, nor a part #. It is apparently called the "Final drive work fixture" but searching for that gave me no love anywhere. I'm going to try to reach out to Wanganstyle on r3v....

Anyone else got ideas?

[bk_856er]

Sounds like you need a simple fixture to hold the pinion flange and prevent it from turning.

I rebuilt the differential in another vehicle a while back. The 4x4 guys have lots of experience with differentials and some have developed good hacks that you might be able to take inspiration from. Peruse gearinstalls.com or similar for ideas - check out the "tools needed" link on that particular site and scroll down for an example of a simple homemade fixture. Zuk is a differential jedi master.

BK

[bk_856er]

From the book. Factory holder is 230020, used in conjunction with a diff bench stand. I'd use some angle iron...

[Mike W.]

I got my seals and crush bushings from Blunt and got going today. Stymied:



I was able to get the pinon nut off by using a pry bar thorough a hole in the flange, wedged against the case, using the impact hammer.

However, the diameter of the flange holes are such that not even the hardest-steel drift I have is strong enough to withstand the torque required to crush the crush bushing.

I'm now in search of someone who has the special BMW tool designed for this. I have not been able to find any pictures of it, nor a part #. It is apparently called the "Final drive work fixture" but searching for that gave me no love anywhere. I'm going to try to reach out to Wanganstyle on r3v....

Anyone else got ideas?

Not a problem. I made one for a challenge something like this, the front hub nut and seal on a M52. You need a piece of flatbar, say 3/16"X2" a couple of feet long. Or 1/8"X4" You've got options. Simply drill for the driveshaft holes, bolt it up tight, attach something as long or longer than your big cheater you're going to be using and away you go. Thick enough and you can use 2 holes, a little thinner and use 3 or 4 with a cutout. This is the easy part, don't let it slow you down.

[tig]

Not a problem. I made one for a challenge something like this, the front hub nut and seal on a M52. You need a piece of flatbar, say 3/16"X2" a couple of feet long. Or 1/8"X4" You've got options. Simply drill for the driveshaft holes, bolt it up tight, attach something as long or longer than your big cheater you're going to be using and away you go. Thick enough and you can use 2 holes, a little thinner and use 3 or 4 with a cutout. This is the easy part, don't let it slow you down.

Thanks Mike. I don't think I could be going any slower. Good thing I don't need to be doing this.

[tig]

Duh.

Why didn't I think of this before?



Nailed it the first time too. I had bought a 2nd crush bushing just in case, but I was just super careful getting to 25in/lbs.



Checked the torque on all the fasteners and marked them (made me feel like a pro).



I do believe that is just about right. Whew. Turns out that the spacers DO go with the case, just as others have indicated. I thought I might have had them reversed too, even though I labeled them right/left...I couldn't remember if I had done left/right looking forward or left/right looking back! (It was forward).



Off to a dinner party... will check it again, and then finish putting it all back together!!!!

[tig]

Done!

That was kinda fun. I'd do it again.

[Mike W.]

Done!

That was kinda fun. I'd do it again.

Wow, looks good! Granted what's important is inside, but it almost looks too good to hide underneath.

[wkohler]

Why did you paint the drive flanges?

[tig]

Why did you paint the drive flanges?

Because I figured they will rust otherwise. I plan on wire-wheeling off the faces; I meant to mask them but forgot.