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Stiff 1st gear gate on 4 synchro remote box (4 replies)

Dearg
6 years ago
Dearg 6 years ago

I have recently rebuilt my 4 synchro remote gearbox using a straight cut C/R gear set from Minispares. The box functions fine with no crunching between gears

Dearg
6 years ago
Dearg 6 years ago

I have recently rebuilt my 4 synchro remote gearbox using a straight cut C/R gear set from Minispares. The box functions fine with no crunching between gears but engaging first is a herculean task. A straight run at it almost always leads to failure to engage and the only way to reliably get 1st is to select 2nd to start with and rapidly slam it into first. It might as well be a 3 synchro box.

I stripped, greased and rebuilt the remote and, when not connected to the gear case, it is smooth as silk. The anti rattle springs, plungers and nylon cup are all in good order so I think the problem is not here.

Has anyone any bright ideas as to the cause of the problem. As I say the box works fine apart from difficulty in the selection of first.

ROLI
6 years ago
ROLI 6 years ago

1: Have you replaced the bush on the remote
2: Are the male/female knucles the correct way and are they not worn.
3: Is the primary gear bushes ok ? It could make the clutch plate not de-engage
4: Have you checked the brass fork for 1st/2nd gear
5: Is the synchro hub (1st/2nd) not worn ?

Of the 5 its most probably 4 and 5, sorry
ps, where are you in the uk ? I know someone who builds all the mini7/miglia gearboxes, hes done my s/c and its brilliant...

Dearg
6 years ago
Dearg 6 years ago

~~ You may recall that I was complaining that 1st was next to impossible to engage whether with the engine running and on the move or stationary or with a dead engine.

Having checked all the external linkages I pulled the engine and box and stripped it to the mainshaft. It had seemed that the 1st-2nd synchro hub was jamming for some reason. This was stripped rebuild and re-assembled but the problem was the same. A spare synchro hub was used and the same problem.

Carefully watching the action of the change speed gate and change speed operating lever showed that the lever was travelling further than necessary and carrying with it the forward arm of the change speed gate to an extent that it engaged the 1st 2nd selector rod and so blocked it.

Further study showed that the stop on the gearbox main centre bearing retainer was too far to the rear by 40 to 60 thou. If a shim of 50 thou was added to the stop face, then the over throw WAS CURED AND THE BOX WORKS PERFECTLY!

This was a goldseal box originally and perhaps the tolerances on the change speed operating lever and the stop on the bearing retainer were at opposite ends of the tolerances. Simply adding some weld to the forward face of the stop on the centre main bearing retainer and filing it back until there was no excess overthrow got the job done.

Thanks for your suggestions Roli, they took me in the right direction.

minicentie
6 years ago
minicentie 6 years ago

You should have made picture's ,it explain's a lot more . I am having some problems with a 1128 but it didn't got used for over 30 years.
First i want some ours of use in it to get everything used again.

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