Sprite Ribcase Gearbox Overhaul

Started by MiniDave, July 19, 2016, 02:37:27 PM

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MiniDave

I know this is outside what we usually talk about but it's something for me to do while waiting for Mini engine parts to arrive, and it's helping me make yet another connection for both new work and parts.....so......yay!   ;D

The customer actually sent me three complete gearboxes with orders to make one good one, one of the gearboxes turns freely, the other two do not. The free one was recently worked on by someone who admits that he knows nothing about working on gearboxes - cars either I'd bet, based on what I'm seeing.......which is parts missing (like detents that keep the box from going into two gears at once - fairly critical) and parts not installed correctly, old gaskets reused, bearings missing shims and the wrong gearoil in the box (these use 30 wt motor oil, he had 90 EP gear oil in it....)

So, this is what I started with....on teardown it didn't look too bad. Everything was pretty clean inside at least......
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#1
First thing I did after stripping the case was take them up to school and use the bead blaster.....they're not perfect but about a million per cent better than they were.....the customer was suitably impressed when I sent him this pic!
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#2
Next came inspection of the gears themselves, most are in pretty good shape. There is some wear on the 1st gear, but as this box is not synchro'd on first that's to be expected.

I did see some damage to the coating on the synchro areas of a couple of the gears but I think this is still serviceable.

I bought an "overhaul kit" from Victoria British for about $150 which includes all the paper gaskets nd oil seals, a new layshaft and it's roller bearings, new synchro balk rings, new mainshaft bearings and the idler bearing.

However, I now have an issue to resolve -  as the previous guy clearly did not know what he was doing...... the replacement mainshaft bearings are .625 or so thick, the OE bearings were .720, so they provide shims. The previous guy replaced the bearings but did not use the shims, and as I don't trust his workmanship I have to figure out what shims to use and where they go....still working on that......

The last pic shows there were no shims behind the main bearing......

Next installment, I'll disassemble the entire mainshaft cluster, replace the rear main bearing and synchros and check to make sure all the detent balls and springs are present and in the right places.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

Jims5543

I shall watch this with great interest never been inside a gearbox in my life.
Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride! -Hunter S. Thompson

MiniDave

They're not all that difficult, but there are some "tricks" you need to know...like the hubs on 3-4th gears have three detent balls in them, I can hold two but don't have enough hands to hold three and slide the hub over the detents, the answer is a hose clamp to hold them in place, then just tap the hub on.....

There also is a distinct sequence to both disassembly and reassembly, get it wrong and either you take it apart again or something gets stuck......
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#5
Reinstalling the layshaft and gear is kinda "fun"....those two bushings have to go in with the gear, which lays at the bottom of the box to provide room to get the mainshaft gears in place, then you raise the laygear into place and slide the layshaft in without losing the two bushings on either end!

How does he do it you say?

Simple, I cut the old layshaft off slightly so it's the exact length of the laygear and bushings, put it all together and drop it in place. When ready to install I shove the old layshaft out by pushing the new one in.....

Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#6
I had to take a day away from the gearbox build to work at one of my other jobs and then another day to handle some things at school before the fall semester starts.

With that out of the way I got a little more done on the gearbox tonight, I changed out both main bearings and disassembled the rest of the main shaft...the synchros were absolutely toast! Worn down to nothing, I don't know how they even shifted gears with them so worn. I put the new synchros in and assembled the shaft, but once together I realized that whoever worked on it before left out the detents that hold the 1st/2nd gear sliding sleeve in place so I get to take it back apart again and make a trip up to Vicky Brits to get some detent balls and springs. The rear main bearing was not seated in it's housing properly either

The kit came with a new layshaft and needle bearings and I see why they recommend changing it anytime you strip one of these down - it had heavy wear in the shaft.

So tomorrow, I finish cleaning the cases - the one downside of using a bead blaster is that bits of the glass embed themselves in the aluminum and you really have to scrub it to get them all out. Then I can go ahead and put it all back together.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

Another day in the shop......I now have the mainshaft all assembled and ready to go back in the case, it did involve 2 trips up to Victoria British tho, when my neighbor buddy came over and said "what's this" as he slid the 1st gear operating sleeve off the hub and sent three tiny detent balls and springs flying everywhere! This was my second trip up there as in the am I found it had no detents at all, so I went and bought a set. We found 2, so I had to drive up again, this time I bought all they had in stock - 5 detent balls and three springs.......

So that's all done.....

I also replaced the caged needle bearings in the laygear, changed out all the synchros, shimmed the bearings correctly and tightened all the locknuts and bent over the locktabs.

Today I cleaned the cases up, tapped all the threaded holes, cleaned the threads on all the studs and got everything ready to re-assemble. One of the downsides of using the bead blaster is that tiny glass detritus gets everywhere, every threaded hole, every passage everything has to be wire brushed and blown out repeatedly......the cases look great but it's a lot of work!
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#8
Things were going so well, I was figuring out the right sequence of reassembly, I had the laygear in place, reverse gear in place next up was to insert the first motion shaft, when this happened......

The gears have a coating where the synchro rides (Mini gearboxes do also, so it must be a BMC thing) that sometimes chips or fails. This one had some chips in it but they didn't look fatal, but as I was pushing the 1st motion shaft into place in the case a big chunk of the coating came off. There is no way to fix it, and these parts are rare!

You used to be able to buy the coatings, they are some sort of compressed metallic fibrous stuff, you heat it to 250*F then slip it over the gear and immediately quench it, then you have to grind it to the right profile - none of that is done today and the cones are NLA, along with the gearshaft. MiniMania had one, they wanted $400 for it but I found a used one for $100 on Ebay, then I got lucky and found a NOS one for the same price - it's wending it's way to me now from Ca.

Till then, I'm stopped on this job.......it may get here on Sat. Too bad, I would have had it all done by tonight.....

In the first pic you can see where it was chipped - the synchro doesn't ride there so it didn't matter much, till the big chunk just fell off. Now all its good for is as a clutch alignment tool......
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

jeff10049

Cool project Dave Thanks for posting.

Very similar to the early mini box where the friction material is on the gear rather than the ring not a very serviceable design this type use steel syncro rings. Looked like their may have been a brass one mixed in the pic you took it might just be the coloring and im sure you all ready know that but you don't want brass rings in that trans.

A couple ways I have fixed those is to keep the steel sync ring and press a silcone bronze ring on in place of the broken mystery friction material and then turn to final size and taper works fine as good as the stuff that broke off. Or press a 4140 steel ring on in place of the friction and switch to a brass syncro ring they are the same size, this is the better choice because then the wear item becomes the easily replaceable syncro ring.

Sometimes the steel rings end up in the later trans that has a steel gear hub and of course they don't work I have fixed two that had that problem where the car owner got the cheapest stuff he could find and ended up one or two steel syncro's in a later trans.

The early three sync mini used a silcone bronze friction against the opposing steel gear they are also nla I made two of mine and shrunk them on and turned to final size.
It works great I used aluminum bronze and it works well but silcone bronze is what most factory syncro's are made from.

You have this one worked out but thought I add this for future projects or readers they can be repaired if you have or want to.

Here's one of my mini syncro's that I redid.

MiniDave

Hang on, let me make sure I understand you - brass on the hub with a steel synchro is OK, right?

Because I think the NOS shaft I bought has brass on the gear as the friction material........

Maybe I could send this old gear off to you for a refurb? Other than the synchro surface it was in great shape.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

jeff10049

You're good to go if the gear has brass you want a steel synchro. And thats what that trans should of had.

I would be happy to refurb one for you or anybody if needed I would use a brass material just like the nos one you bought or steel and you would then have to get a brass synchro up to you. If you ever have me do one I need a good synchro with it to get the fit right.

Jeff

MiniDave

Cool, I may have two more of these gearboxes to do for the guy, we'll see what he says after I finish this one. The synchros are definitely steel.

It's great having access to machinery like you do, I'm glad I have what I do at school - we have lathes and mills and such there too but as I'm not an instructor in that dept I'm not allowed to use them - so I just get access to the car shop equipment..
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

jeff10049

Times have changed I seem to remember other teachers using whatever they wanted with permission and a quick safety test. But that was 20 years ago, damn i'm getting older. I even took a class in high school where we did metal casting bet those are gone.

If you were near you could come use my stuff anytime but I can sure do them if you end up needing. I have a fair amount of aluminium bronze left from other transmission projects.

Jeff

MiniDave

I think the only metal casting done in our school is in the art/sculpture dept!    ;D

We'll see what happens once I get this one built, I haven't taken either of the other two apart, he says both are "locked up", I've never seen a gearbox locked up from rust like an engine unless it's been stored under water or open, and both of these are oily, dirty and complete enough that's not the case, so I'm guessing jostled around enough that somehow they've dropped into two gears or something.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

#15
I bought a roll of butcher paper to cover the lift table surface, this keeps things cleaner and makes it easier to find that odd bit I might have misplaced.

The new shaft should be here Sat, hope it's the right one.....if not I'll be sending this old one off to Jeff to work his magic on it!

The last pic is of the other two gearboxes waiting their turn....



Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

Well, the new first motion shaft turned up today, a few days early but unfortunately it's not the right one for this car. However, the good news is he has a Bugeye Sprite with the smoothcase gearbox that has grunchy gears and needs overhauling too, and guess what this one fits?

So no loss at least.....but now I'm back trying to find a solution for this one and possible the other two if their synchros are in the same shape....that's just cardboard dust and cosmoline on the new one.....
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

Had a great conversation with Jeff10049 and we think we have a way to fix this gear, so I'll box it up and get it on the way to him and hopefully he'll have some pics to add sometime in the next week or two. Thanks Jeff!
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

jeff10049

It's here.

Started with some measurements. Then removed the rest of the friction material and polished up the surface.
It is hardened enough to run a bronze synchro on it. So I decided to see if one of  the used steel synchros would cut ok  on the lathe, it did very soft steel.
So it was bored out and will get a c954 aluminium bronze insert bored to correct taper to run on the gear hub.
Started at the business on the old atlas lathe then got home dug out the aluminium bronze and enlisted the ole sawmaster power hack saw to cut off a chunk for machining.






Jims5543

I have fallen behind on this thread due to vacation and being behind at work.

Just caught up with this thread (still behind at work) and wanted to say it is a blast to read.  Kudo's to Jeff for jumping in to do some fab work.

Dave, your knowledge and Jeffs as well is really amazing. I am reading with great interest.

Carry on.    ;D
Life should not be a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside in a cloud of smoke, thoroughly used up, totally worn out, and loudly proclaiming "Wow! What a Ride! -Hunter S. Thompson

MiniDave

Thanks Jim, we both had the ideas, but Jeff has the skillz and equipment to make it happen!

Jeff, how much did you take out of the synchro, and how thick will the insert be?
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

MiniDave

After talking with some Sprite gearbox guys in the UK, come to find out the surface that was damaged on my gear is some sprayed on metallic stuff, not replicatable now (at least cost effectively) so Jeff's idea may be the only way to fix these in the future. There may be a few of these gears NOS somewhere, but I sure couldn't find one and the UK gearbox guys say all they have are used ones.
Complete failure at retirement

1989 Cooper Racing Green
2009 Clubman S
2014 Audi Allroad

jeff10049

cut the synchro straight took .100 out of synchro thick side about 20 out on thin side that minus the thickness of the coating will make the insert about .125 on the thick side and about .050 on the thin with about .030 remaining at oil the groves on the thin side. And .068 remaining on the steel ring.

It's interesting you found out about the spray coating I was thinking about a spray welding of some kind as it looked spray welded to me. Something like A Molybdenum alloyed cast repair spray could maybe work I do have the equipment to do that, but i'll leave that for another day figuring out a suitable coating will take some digging then it still may not work.

I did save a chunk of coating at some point I will have it XRF tested to see what it is just for fun.



jeff10049

#23
working on the jet 12x36 lathe at home today got the aluminium bronze roughed out at the shop in between stuff yesterday. chucked it up here and finish turned the od for a .003 interference fit into the old synchro. heated up the steel part and coated the bronze with locktite and tapped them together. I ended up just using the new steel one you sent as I could not get oil to stop coming out of the used one when heated that was also affecting the surface finish when machining.

Next I swept the taper of the shaft with a indicator to find it was a 9 degree taper. set the compound chucked up the bronze lined synchro and cut the taper to size. Then the round grooves. Next a parting blade on its side was used to manually cut the oil relief slots buy cranking the carriage in and out.

It fits well even sticks on there you can pick the shaft up buy the ring so the tapers match well. IT feels like it should have plenty on braking force when turing by hand.




jeff10049

#24
more pics, Also if you would Dave check the height of a good sync and hub this one has lots maybe too much I imagine it'll wear somewhat quickly at first I just don't want it binding up I don't know how much wiggle room their is I can always take one more light pass.

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