Diff leak confirmation and question about difficulty

[Hodgepodge]

Hello all,  

 

Well, it is weekend and I'm off to a really slow start tearing down the front and rear subframes.  Taking pictures of EVERYTHING prior to doing anything.   

I was pleased to learn that none of my CV boots are broken, even though everything is covered with oil-crud.  Hard to believe that diff was originally black.....

 

I invite those who are familiar with the short rear diff to look at the images below.   I need confirmation on the most likely sources for the liberal amount of oil/grease all over the rear drivetrain.  I know the rear gasket is leaking and it is likely that the drain plug is also leaking (assuming that the diff oil was ever replaced).  I also think the shaft seals on the output sides are leaking, which accounts for most of this crud...I think.  What I'm not sure about is what it would looks like if a CV-joint is throwing grease.   The outside boots are dirty but not greasy.  The inside boots are greasy/oily.   Of course, I haven't cleaned a thing yet.   I plan on replacing the CV-boots and cleaning up/re-greasing the CV-joints while I am in there.  This is really about the diff. 

 

My inclination is that all of this crud is coming from the gaskets/seals/o-rings/drain on the diff.  Your thoughts?    

 

 

Ireland Engineering sells a diff rebuild kit now.   Has anyone used it and how hard is it to JUST replace seals and bearings?   It is not making any noise that I know of.   Gotta get it cleaned up first.  What a mess...

 

Link to new IE rebuild kit....

 

Small Case Diff Rebuild Kit

 

Adams Autosport also has a diff rebuild kit with the correct yellw zinc bolts and timken bearings.  

 

Adams Autosport Diff rebuild kit

 

  

 

As always, thanks for your input!  

 

Scott

 

 

 

 

Edited March 25, 2018 by Hodgepodge

[Mike Self]

16 minutes ago, Hodgepodge said:

What I'm not sure about is what it would looks like if a CV-joint is throwing grease.   The outside boots are dirty but not greasy.  The inside boots are greasy/oily. 

If the CV boots were torn/leaking, there would be a streak of grease/dirt all around the inner wheel well, aligned with the boot tear--and very noticeable.  The grease on the inner boots is from leaky side seals.  "They all do that."

 

In general, diffs all seem to dribble, especially after 40+ years.  With the diff out of the car, replacing the rear cover gasket is easy, as are the side shaft seals.  The input shaft seal, though is a whole 'nother can 'o worms.  Do some reading up on that before tackling.  

 

My original diffs have 225k and 260k miles respectively, they leak a little and I just put up with it and make sure there's the requisite amount of hypoid oil in the housings.  I have a 3.64 LSD lurking in the garage that I will re-seal before installing, though--just on general principles.

 

mike

[wegweiser]

The disassembly / adjustment / re-assembly is fairly straightforward. If you have a copy of the BMW blue Shop Manual, this will clear up some of the mystery. 

 

If you do not yet have a real Factory (blue binder type) manual... now is a great time to get one. They are out of print, but used ones generally change hands in the $100-150 range and come up for sale frequently. Worth every penny. 

['76mintgrün'02]

... and in the meantime, there is this one.

 

[Hodgepodge]

21 minutes ago, wegweiser said:

The disassembly / adjustment / re-assembly is fairly straightforward. If you have a copy of the BMW blue Shop Manual, this will clear up some of the mystery. 

 

If you do not yet have a real Factory (blue binder type) manual... now is a great time to get one. They are out of print, but used ones generally change hands in the $100-150 range and come up for sale frequently. Worth every penny. 

I have an electronic copy of the blue manual as well as a bunch of other books and 2 copies ('76 and '17) of the Haynes manual.  I am always amazed that there aren't really any newer "working" manuals out there, but it is the same with other cars I own as well.  

 

I am going to pick up the IE rebuild kit and give it a try.  

[Schnellvintage]

You can definitely rebuild them. I just rebuilt one for my brother’s 02..new bearings, crush sleeve,o-rings, seals and gasket. I have 3 more I need to rebuild. [emoji3]
PM me if you have questions.
Matt



Sent from my iPhone using Tapatalk

[Hodgepodge]

21 minutes ago, Schnellvintage said:

You can definitely rebuild them. I just rebuilt one for my brother’s 02..new bearings, crush sleeve,o-rings, seals and gasket. I have 3 more I need to rebuild.
PM me if you have questions.
Matt
 

 

That looks very nice!   I am probably a few weeks away from a rebuild but I might take you up on that offer if I run into any issues!  

[NYNick]

If it ain't broke...

 

I just cleaned the living bejesus out of the diff while it was still closed up so no crud could get inside, then opened and cleaned (and inspected) the inside (plastic not metal brush), then painted and resealed it. Scope creep is out there every step of the way otherwise.

 

By the looks of it you're gonna need a new Diff Carrier too. $83 I think from Blunt.

 

Oh, and Rear Carrier bushings with Prothane inserts (optional), trailing arm bushings, new sway bar and (urethane?)bushings and drop link grommets, new Springs and shocks, new stainless brake lines, new hard lines (optional), new wheel cylinders, shoes and drums. Not to mention sanding and painting the subframe.

 

Hope you have some time on your hands. : )

[Hodgepodge]

NYNick,

 

All good observations. :-)   I'm on top of nearly all of that.   I'm going to take the subframe apart today.  I'll wait to buy the rebuild kit until I've cleaned it up a little.  

 

What piece is the diff carrier?    Do you mean the rear cross member?   33173404100

 

Real OEM rear diff

 

Blunttech rear crossmember

 

That makes sense since I don't see the bushing inserts sold separately. 

 

I have all new urethane bushings from IE, their swaybar kit, their braided flex lines, their stage-1 springs, new shock pads/covers and new bilsteins.  The all new hard brake lines are on their way from Andrew.  I also have new pistons, drums and wheel bearings as well as new plugs and crush rings.    

 

I plan to have the subframe components media blasted (lightly) and powdercoated, depending on how they clean up.  

 

And there are CV-joints to rebuild....

 

Yes, lots of time.....  

 

 

 

 

 

          

Edited March 25, 2018 by Hodgepodge

[NYNick]

Yes, that's the Cross Member I was talking about. All new urethane? I was advised that will result in too harsh a ride for my taste and I like firm suspensions.

 

Just did all this. Took me almost the same amount of time to clean it than it did painting, reassembling and reinstalling. Of course, I'm retired so it's my job now. That, and going back and forth to Florida to play golf. LOL

 

Part of my problem is I work in spurts because I'm not home much with all my traveling, but the suspensions are all done now. Next up, the engine. Clean clean clean.

[TobyB]

Since no- one else said it:

 

Looks to me from the pattern of your splattern like the overflow's plugged up...  perversely, it'll leak if it can't breathe,

or if it's overfilled with something that gets foamy.

 

Also, "rebuilding" a diff is a major job.   

The first one takes a long time to get right, and may eat more than one

pinion seal, crush washer, oil slinger (depending on variety) etc.

 

Resealing everything but the pinion is very easy,

and from the looks of your spray, you can do just that.  

 

t

 

[Hodgepodge]

Thanks Ray, that makes perfect sense to me.  The whole thing is covered with crud and the breather/overflow isn't working, I'm sure.  Given that the cotter pins on the axle bolts have been re-used, I'm guessing the crush washers have never been replaced, either.   I have the subframe apart now...mostly.  And it might actually break 50 degrees within the next couple of days, so next step is to clean everything with actual water!   I am starting to see that, like previous british cars I've owned, liberal amounts of misplaced oil often act as an excellent rust inhibitor and paint preserver.   

 

  

 

 

 

 

[Buckeye]

20 hours ago, Hodgepodge said:

Your thoughts?    

 

 

take the diff off of sub frame and spay it with your favorite de-greaser and let it soak for a day. Then take it out and use pressure washer to really clean it out. Put you mouth on that breather pipe and blow. After while you won't be able to blow in. Let go and will hear air exiting the cavity. Paint it with your favorite color and is done. Or at least that is what I did and I been monitoring leaks for 1-1/2 year and have not seen any.

[NYNick]

I cleaned the breather with brake clean. Just stuck the straw in it and pressed "go".

[Hodgepodge]

Well, I'm certainly going to clean it well before opening it up but I'd hate to get it back on the car and have it start leaking.  ....Although it would be much easier to just pull the diff then...

 

Much to ponder...  

 

Thanks,

 

Scott