There's some discussion on the shift fork in this thread, including a suggestion from the Doc to use a modified 3 synchro fork as they are more readily available. That's what was done to my 4 synchro box rebuild by a very reputable Mini mechanic.

viewtopic.php?f=2&t=96523

_________________
ex-NSW Police 1970 MK II Cooper S
VMCI #43

I've heard of using a modified three synchro, did they modify a brand new fork or a good used one?
I have a few 3-sync gearboxes, thinking I'll pull some apart and see how the forks are for wear and how they fit

At the time I believe NOS or new repro were readily available so preferable of course. Don't know about now. Maybe search the usual suppliers.

_________________
ex-NSW Police 1970 MK II Cooper S
VMCI #43

I stripped two 3 synchro gearboxes on the weekend, and both forks were better than the 4 syncro one.
I had a look at how to modify the fork to clear the case and reverse selector, and this the seems like the way to go

I have a NOS fork if you need one.

I'll message you.
What does the new one measure inside? My best used fork is around 11.9mm where it runs on the sides of the gear. I Think the gear is around 11.5mm
I'm at work so can't double check now.

I'm in the final stages of getting this 4 synchro remote gearbox finished.
I started to drift the bearing for the transfer gear into the gearbox casing (bearing 13H7848) and can't see how it's supposed to sit.

There is a bore straight through the Webb of the gearbox for this bearing. This bore has two circlip groves, the inner one has a circlip fitted.

If that bearing is pushed in so it rests against that circlip, it is then very deep in the casing, and the rollers of the bearing are then no longer fully under the idler gear shaft.
I think the bearing should just sit flush with the face of the gearbox casing? but then what are the circlip grooves for?

On my old 3 synchro gearbox i looked at, there doesn't seem to be a circlip or anything to retain the bearing, and no circlips at all

here's some pics

I would say if the circlip groove is there, it should be used.

That was my thinking too, but then if the bearing is installed to that circlip the bearing doesn't fully support the shaft.


I pulled the cover off another 3 synchro box, and it also has the bearing mounted closer to the idler gear.
Both my 3 syncro gearboxes have circlip grooves that seem to be in the "wrong" spot and no are circlips fitted.
One 3 synchro box had the bearing 2.1mm back from the face of the gearbox housing and the other 2.7mm.
If the bearing is pushed home to the circlip it's about 7mm back from that face.

This 4 synchro had some "interesting" things done during a past rebuild, so I don't trust that the circlip is supposed to be there.

Idler gear 22G943 has a longer shaft.

I went and had a look, and one of the 3 synchro boxes had a longer shaft primary in it.
As you can see by the marks from the bearing, it was not pressed in any further than what would have been required for the shorter shaft.

So, seeing that I have this; would the best course of action be to have the bearing pushed home against the circlip, and then use this longer shaft?
Is there supposed to be another circlip on the other side of the bearing? there is a groove there also

There is a circlip on both sides of the bearing.

The gear with the longer shaft is correct for the 1128 gearbox casing.

_________________
did I tell you that I won a trophy?

Update.
Susanna is now back on the road with the rebuilt gearbox, and I've been doing laps of the local suburbs this week.
The new 4 synchro is great, It's never crunched at all.
First gear is a little tricky to get when stopped, but not too bad, it might get better once it wears in a bit?

Very happy to have it all fixed.

Thanks To cooperess for the shift fork too!