13 replies to this topic

[alex-95]

I'm planning on rebuilding my G/B next weekend, so today I'm inspecting everything so I can get bit's if required. This gearbox was stopped and rebuilt but a G/B specialist and has done 8 (yes 8) miles since due to one of the baulk rings splitting. 

 

First thing is the bush in the diff crown wheel. measuring with callipers the output shaft diameter was 26.1mm and the bush measured 26.24mm, this seems quite a lot of play? I found a thread saying it should be about a thou (0.025mm), is this right?

 

Measuring the selector forks I get the 1st/2nd (pretty sure it is )one I can get 17 thou in, which reading says that 30 thou is when it's scrap? so should be good to use again?

 

The 3rd/4th. This one Was what was i the box originally (unless swapped by G/B specialist) There is quite a bit of wear on it reading 11.6mm and has a big step in it as photoed. The synchro hub width measures 10.6mm

 

 

The rest is spares that I've got from G/B's that I've stripped. They all measure pretty much the same at 10.8/9

1. SR15

 

 

 

2.SR24

 

 

 

3.SR23

 

 

Looking at them, I think the no 3 looks the best? Does the numbers on them matter? as the original one has a complete different number to the others.

 

 

Cheers Alex

[Spider]

Alex, sorry, I'm still on old money for these measurements.

 

The shafts on the diff are (from memory) 1.050". I set the clearance on these to the bushes at 0.0008 to 0.001". They can be a little on the tighter side as they are not (or shouldn't be !) spinning too often.

 

The factory data on the selector forks is a maximum wear limit of 0.015". The original Leyland ones I was supplied long ago when new were from 0.000" (no measurable clearance) to 0.003". There's been many of the 1st / 2nd Forks I've been supplied in recent years that have been outside of this spec, right out of the bag.

 

The Photos of the selector forks for me aren't enough to go on, however No. 1 is toast, 2 and 3 look like candidates. Check the fit and clearance.

 

That fork rarely needs replacing (probably 1 in 8 or 10 boxes) as it has faces on that that are almost 180 degrees, the one for 1st / 2nd nearly always needs replacing as it only has 4 small pads for contact.

[alex-95]

Alex, sorry, I'm still on old money for these measurements.

 

The shafts on the diff are (from memory) 1.050". I set the clearance on these to the bushes at 0.0008 to 0.001". They can be a little on the tighter side as they are not (or shouldn't be !) spinning too often.

 

The factory data on the selector forks is a maximum wear limit of 0.015". The original Leyland ones I was supplied long ago when new were from 0.000" (no measurable clearance) to 0.003". There's been many of the 1st / 2nd Forks I've been supplied in recent years that have been outside of this spec, right out of the bag.

 

The Photos of the selector forks for me aren't enough to go on, however No. 1 is toast, 2 and 3 look like candidates. Check the fit and clearance.

 

That fork rarely needs replacing (probably 1 in 8 or 10 boxes) as it has faces on that that are almost 180 degrees, the one for 1st / 2nd nearly always needs replacing as it only has 4 small pads for contact.

Thats alright, quick change on google and I understand  

Thanks for the help.

 

oh yeah, didn't think about them not spinning that much, but mine seems a lot more than a thou. Now it's wether to bore out a new bush in the 3.44 or buy a new 3.2 ratio diff.

 

Ah ok, I'll have a look at my other stock for the 1st/2nd forks to see if they're any better.

 

That makes sense, I'm going to ultrasonic clean all the ones I've got so I can check them for size and go from there.

 

Does anyone now what the sr numbers stand for? batch number?

 

I've got a couple of the 1st/2nd forks like the minispares ones and one like the minisport type, is one better than the other?

https://www.minispar.../TSP100390.aspx

https://www.minispor...ynchro-rod.html

[Spider]

The new forks may all come from one supplier ??? I don't know, however, I've had better luck with those from Somerfords than most others, maybe theirs are better, or maybe just luck?

[ACDodd]

Also check the selector fork where it contacts the bell crank. Standard is 0.500" slot width. If it's 0.512" or more it's junk.
I am with moke on the diff bushes, just under a thou clearance on the output shaft is ideal. Yours is too much.

Ac

Edited by ACDodd, 08 October 2018 - 11:22 AM.

[alex-95]

The new forks may all come from one supplier ??? I don't know, however, I've had better luck with those from Somerfords than most others, maybe theirs are better, or maybe just luck?

Ah right, If I need to get one then I'll get it from somerfords then. cheers

 

Also check the selector fork where it contacts the bell crank. Standard is 0.500" slot width. If it's 0.512" or more it's junk.
I am with moke on the diff bushes, just under a thou clearance on the output shaft is ideal. Yours is too much.

Ac

Cheers Ac, Will check that. I thought it was bit much on the diff bush, pretty annoyed with these worn bits that should have been checked, the diff was one of theirs that I asked to be swapped

[ACDodd]

Alex gearbox builders don't check this as they simply can't afford to in the price they charge to rebuild a gearbox. Currently a gearbox built to my spec is more than £1200, and more than 3/4 of that is the parts prices.

Ac

Edited by ACDodd, 08 October 2018 - 06:14 PM.

[Spider]

Alex gearbox builders don't check this as they simply can't afford to in the price they charge to rebuild a gearbox. Currently a gearbox built to my spec is more than £1200, and more than 3/4 of that is the parts prices.

Ac

 

I gotta agree, gearboxes I'd say would be one of those items that you'd really only get what you pay for. I used to do them as part of my business many years ago and hate to think what one would cost to have done now (though AC's price here is a good guide), in particular, they way I go about them these days, it would be prohibitive.

[Retroman]

Unfortunately many Mini owners think £600 for a  'reconditioned'  gearbox is a lot.

 

In reality its a long way off, they were £750 twenty five years ago

 

Perception is changing slowly but people need to realise a Mini is no longer a cheap car

 

The days of a £300 rebuild are long gone

[alex-95]

Thats a fair enough point, Just seems a bit pointless putting in worn parts back in. If you're going to do something you may as well do it right... But thats not what this thread is about so...

[grizzler73]

I'm doing mine myself and the parts alone are around 400 notes!
Luckily I have a very low mileage box so most of the parts are in good nick.

[alex-95]

Anybody else recommend where to get the 1st/2nd selector fork? Somerfords have sold out and so have minispares.       minisport, rimmerbros, bull motif?

[Spider]

Bull Motif appear to have them, but I don't know what the quality and fit will be like;-

 

https://bullmotifmin...dam7425_22g1855

[alex-95]

Bull Motif appear to have them, but I don't know what the quality and fit will be like;-

 

https://bullmotifmin...dam7425_22g1855

Thats the problem, looking at the photo's of it, it looks pretty poorly made as there isn't much contact area after it's been machined (pretty sure the original ones are a bigger contact area).