901 gearbox visual inspection

[kium]

Hi guys,
what do you recon of this teardown gearbox?

Bought it on a wooden palet, for years unused, with a promise it was ok. Nothing too appealing at first glance.
It's a 901/13, 5 speed, maybe 1968.

Came apart quite easily, still had some oil inside, about 1L with a "good" smell and a golden color.
I have the impression it's the first time it's taken appart, the paper seals are extremely thin and came out in one piece, no sealants used. The rubber seals are all Kaco.
The magnetic plug was loaded the classic fine metalic sludge, no metal bits have been found inside.
All parts turn free and smooth.
The reverse switch looks brand new and the speedo gear refuses to leave it's home.

I'm not in favour of taking it all apart just to double check all is fine, I'm not sure I will put it back together as well. I can live with a used gearbox.
Having said this, now it's the moment to fix anything that's needed.

Please take a look and give me your opinion:


Reverse gear and needle bearings (complete and all fixed in place)



1st gear


Differential bearing, right Smooth but with a satin finish


Differential race, right side (lid) Smooth but with a satin finish


Differential bearing, left


Differential race, left Smooth, with a satin finish and oil marks from years not moving


Secondary shaft race


Primary shaft race


Gears 2 and 3


Gears 4 and 5


Cheers, Kium

[john walker's workshop]

Looks decent, on the surface. Disassembly shows a lot more.

[Jon B]

Originally Posted by kium

It's a 901/13, 5 speed, maybe 1968.

Hello Kium,

This is a 69 model 5-speed, with a pressure-cast magnesium housing.

As John said, your pictures don't show any obvious issues, except for maybe a worn synchro ring.
The most common problem areas are the 2 ball bearings in the intermediate plate, and the synchromesh parts in the lower gears.
The bearing bores in the intermediate plate can wear. It has a Simplified Differential, so check the axle flange bolts for worn ends.
Also check the main shift selector shaft, they are often bent to some degree.

[kium]

Thanks John and Jon for your help.
To me it also looked decent, bu I haven't that knowledge to "really see".

Being a sunday mechanic I'm not comfortable disassembling any futher.
Now my maths are if all we can see looks decent, the little we can't shouldn't be any different.
It's just an statistic I know, not a fact.

Looks like in worst case the car will still run but a disassembley and rebuild will have to be done at some point
To me looks like the best option now is to replace seals and a oil and give it a go as it is.
I feel quite confident after your "inspection"

[kevingross]

It is hard to judge bearings from photos unless you're really skilled with a Micro lens. That said, I seem to see significant pitting in the photos of bearing outer races. Assuming that to be true, those bearings need to be serviced. In typical practice given this many worn bearings, it's best to do them all.

As Jon mentioned, there are one or two synchros in need of replacement. Certainly the synchro in the 4/5 photo. But I also may be seeing wear and a "patch" missing in the 2/3 photo. Good luck,

[kium]

Thanks Kevin for your comments, and I do see now what you point out.