003 automatic final drive: ring pinion wear pattern

[Slow 1200]

Ok, so I finally got my 71 fastback titled (thats a story by itself )
and now the only thing that's stopping me from driving is a very noisy final drive, I'm suspecting differential and/or pinion bearings
I know the trans was leaking ATF into the final drive, I don't know for how long it was driven like that, I hope ring and pinion didn't get damaged
The car has only 50.000km and the trans actually shifts nicely, but there's clearly something going on in there! (whining on acceleration and coasting, and the car is actually difficult to push around, feels like dragging brakes but they are adjusted fine)

I got myself a trans rebuild kit, so tomorrow I'm gonna pull engine and trans and start tearing into it.
It's my first type 3 engine pull too, so any pointers are welcome!
Do I need a puller or a press for the bearings or does everything just come apart easily? How can I check for damage to the ring and pinion? What about setting the r&p mesh for the DIYer?

I have the brown Bentley and a copy of the "1968 provisional automatic transmission workshop manual", I know early autos are different at the stub-axle level so I'm wondering how different my 71 is gonna be.

[Slow 1200]

I only had my cell phone with me so not the greatest quality pictures:

Getting the stub axles off was the hardest part, after that it all comes apart super easy
After taking the lock plate out I was able to loosen the pinion nut by hand, is it supposed to be that easy?? The backlash between ring and pinion seemed very large, but not having a way to measure it and being my first transmission ever I have no idea if it was good or not.



Can you guys tell me anything about that wear pattern? I know it's a blurry picture, I'll try to come back with a proper camera
I didn't see any obvious damage to the bearings like seized rollers or blueing so I don't really know what to think

[Slow 1200]

ok, some better pictures now:

[Henryhoehandle]

Looks like the pinion nut backed off (NO its NOT supposed to turn by hand. The nut sits a little past the end of the threads when tight (or at the very least, even).

[Slow 1200]

well if I remember correctly the nut was indeed past the end of the threads (and the lock plate in place), so I'm assuming one of the pinion bearings (possibly the back one) is bad and was allowing for to much axial play

[Henryhoehandle]

Sounds like it...

[Slow 1200]

turns out the teeth are totally worn out

[raygreenwood]

Although the pinion nut backing off "could" and would cause this....its highly unlikely. The pinion nutss on these final drives are physiccally locked with a tang.

What you are seeing is a common problem that comes from driving with Dexron and gear oil mixed when the main seal fails. I keep warning people....7 years or 70k miles on seal kit on 003 type transmissions. I think there was even a VW bulletin at one point.

Although the final drive could run on ATF in very cold weather...and normally runs with 90wt....they will not work when mixed together. The extreme pressure properties are lost. Unlike the type 1 trans....which actually follows a spiral bevel gear layout....with pinion interecting the ring gear at either 9:00 or 3:00 (depedning on how you look at it)....the type 3 (003) transmission and the type 4 004 (manual transmission for 411/412).....use a true hypoid gearing.

Did you notice that the pinionshaft crosses over the ring gear....and has a reversed pinion gear (relative to what you see in a type 1,2,3 manual gearbox)? The pinion gear is held on wit ha snapring.

In these autos and the 004 manual trans I listed....the pinion gear intersects very facr off-axis. they are very quiet, very tight toleranced and very long lasting. They also give extreme pressure gear oils a workout due to the large amount of tooth contact area.

What you are seeing is both oil failure...and commonly later...bearing failure from tooth materials in the oil. The teeth wear first creating more lash. lash acclerates wear...more metal in oil. The bearings wear out like they were on sandpaper.

Ray

[Slow 1200]

yep ray, it did run with ATF in the final drive...too bad because the car has only 50.000km! probably the fact that the car was driven very little during all these years contributed to make the seals go bad even faster (in addition to the well known oil compatibility problem of those seals)
I still have the trans in pieces waiting for a good ring and pinion...seems like I might have found a whole parts car instead, let's just hope the r&p is good in that one, my plan is to take the whole diff assembly out and swap it into my transmission (unless I see something weird this time again of course)

[raygreenwood]

When the pinion carrier is out of the donor....if you have the time and money its really worth it to measure pinion to ring settings, lash etc...first....and then just go ahead and replace the bearings. Even though they can last for eons in these units because the cast steel carrier is so rigid...never any misalignment or twisting that can cause much bearing wear.....the bearings are not getting any easier to find right now. May as well fully extend the life of this thing with new bearings. Ray