1098 Gearbox Rebuild

[culp]

I'm just starting out rebuilding the gearbox on my 1970 Traveller. I'd driven it for a while before the restoration and it wasn't bad it was not too noisy and it didn't jump out of gear. It did, however, make a terrible growling roaring noise in 1st and reverse. This I understand is worn layshaft and bearings. When I got the box out of the car the inside of the bell housing was an almighty mess with black gunge everywhere and there is quite a bit of wiggle in the input shaft. the output shaft is fairly solid

Is it realistic for a reasonably competent mechanic to tackle replacing the layshaft and gears and the front bearing and oil seal? Can I get the gearbox apart without separating the dreaded 1st/2nd synchroniser hub and the ball bearings and springs disappearing off the face of the earth? Is there anything else I should consider?

Thanks in advance

Alan

[les]

Was trying to post a link for a rebuild by the Dorset owners club but although I had it on my homepage, it looks like you now need permission to view it. If true, it’s a shame because it was very helpful. Can anyone else access it ?

[chrischris59]

This the one ? http://www.dorsetmmoc.co.uk/wordpress/t ... ebuild.pdf

[pgp001]

You will more than likely find that the first gear ring is well worn judging by your description of the noise.
That was my experience when I did my own recent rebuild.

Its not too difficult to do if you follow those instructions.
The hardest part was fitting and machining the new tail bushing to size.

Phil

[les]

This the one ? http://www.dorsetmmoc.co.uk/wordpress/t ... ebuild.pdf

Yes thanks, that will be the one but the link doesn’t load for me. Hopefully it will for culp.

[culp]

Oh you beauties! Just what the doctor ordered. My membership fee just paid itself back, thanks to one and all for the pointer.

[don58van]

Hi culp

Please let us know how you go. Pictures would be good.

BTW, there are tips on here on how to avoid the springs and balls firing across the room on this site. I bought a little gadget off the online marketplace to make loading the springs and balls foolproof. It is a cup shaped device with recesses to accommodate the balls and springs. A twist of the cup forces them into place so that the ring can be slid into place.

Wishing you well with your rebuild
Don

[culp]

Hello Don,

Do you have details of the tool? Whilst I am planning to avoid separating the two parts I may well wind up doing it inadvertantly.

[philthehill]

This is the tool you require. It may say Mini but it is the same tool for both Mini & Minor.

https://www.ebay.co.uk/itm/Classic-Mini ... Swm6xdvGrP

or

https://www.ebay.co.uk/itm/Classic-Mini ... SwGf5eMaUT

[newagetraveller]

The lay shaft and needle bearings will invariably need replacing. I have never needed to replace the bearing that the third motion shaft runs in and the only problem I had with a first motion shaft was when the bearing cage disintegrated.
I have reassembled that synchro ring with the springs and little balls using two big jubilee clips and three electrician's screwdrivers.
The thing that you have to be careful about is the three selector forks with their rods and springs and plungers. A mistake here and you will find yourself stuck in one gear or jumping out of gear.

[culp]

I have the gearbox apart, so far so good.

the front cover is leaky and the first motion shaft has lots of runout. New bearing

gearbox front cover

PXL_20201212_180616984.jpg (3.36 MiB) Viewed 4567 times

the selector fork rod detent grooves seem fine to me

selector fork detent grooves

PXL_20201212_180557539.jpg (2.65 MiB) Viewed 4567 times

There's 8 thou endfloat in the laygear thrust washers, I need to see if that's acceptable
The layshaft seems fine and not too worn
what has surprised me is the reverse idler and shaft which is very....very worn

worn reverse idler bush

PXL_20201212_130335884.jpg (2.28 MiB) Viewed 4567 times

that has lead to very worn teeth on the idler

damaged reverse idler teeth

PXL_20201212_130507797.jpg (624.67 KiB) Viewed 4567 times

which has in-turn worn the teeth on the laygear

damaged laygear teeth

PXL_20201212_180704595.jpg (611.75 KiB) Viewed 4567 times

most of the bits I can get except the reverse idler gear shaft does anyone know of a supplier?

[pgp001]

Talk to Andrew at Mirabelle Classic Cars, he should be able to offer you something.

http://www.mirabelleclassiccars.co.uk/gearbox.html

Phil P

[jagnut66]

Very interesting, with useful links.
I have a non-functioning spare 1098 box sat at the back of the bench awaiting attention, so I suspect this will prove a very useful point of reference.
Best wishes,
Mike.

[don58van]

Great photos.

I can't imagine why the gearbox was noisy

BTW There is a demonstration of the jubilee clip / zip tie method on youtube somewhere--much cheaper than the cup-type tool I referred to earlier. There is also the clear plastic bag method, which can be combined with other methods to stop balls and springs flying into oblivion.

Thanks for sharing.

Don

[Murrayminor]

Great photos.

I can't imagine why the gearbox was noisy

BTW There is a demonstration of the jubilee clip / zip tie method on youtube somewhere--much cheaper than the cup-type tool I referred to earlier. There is also the clear plastic bag method, which can be combined with other methods to stop balls and springs flying into oblivion.

Thanks for sharing.

Don

Get the correct tool, I tried and failed attempting to use a zip tie, the tool makes the job a 20 second affair rather than my wife and I standing in the garage her holding a clear plastic bag and me attempting to press my thumbs into the teeth of the gear, along with numerous unprintable words, only for the springs to do their work and shoot the balls out, even managing to squeeze between my arm, her hand and the plastic bag, never to be seen again.
Whereas with the tool it was a 20 second job, in fact it was that easy I took it apart again just to check it was correct.

Credit to Phil the Hill for pointing me in the right direction of the correct tool for the job.

[culp]

The reverse idler shaft...the very worn reverse idler, is very tight in the hole in the casing.

reverse shaft very tight in gearbox

PXL_20201215_214045865.jpg (2.05 MiB) Viewed 4420 times

My measurements (taken with cheap eBay vernier callipers) for the shaft are

0.559" - 0.5615" which is 9/16" if my maths is right

the hole in the casing reads 0.539" - 0.543"

so that's the hole undersize by 20 thou or there abouts

I got the shaft out by belting it with a hammer and heating the casing

I'm thinking I buy a 9/16" reamer an ream out the holes to the correct dimensions

Please, somebody, stop me if this is the wrong course of action

[les]

Well I can’t see why the hole should need opening, it wouldn’t close up in service! I’d get a new shaft before doing anything, and see how that fit. I presume there are no burrs or pickups on the shaft.

[oliver90owner]

You simply do not take accurate measurement of hole sizes with a vernier caliper . Even better digital versions are inappropriate for more the measurements to a few thousandths. Simply the wrong tool for the job.

Even when shrink fitting, the shaft will only be a couple of thous (per inch diameter) larger than the hole (in similar metals).

So the hole will be best measured by measuring the shaft that fits in it.

9/16” is 0.5625” by my calculation. In my experience hole tend to become larger, not smaller (unless the casting was belted with a hammer!)

I would suggest the items are galled, so need cleaning up, and fitting should be by pressing, if it is a tight fit

[Murrayminor]

The reverse idler shaft I fitted to my 1275 gearbox was a nice snug fit, I was able to slide it in with finger pressure once oiled, it came out the same way.
I take it the marks on the shaft in the picture are caused by the removal process?

On a side note I didn't have to use a hammer on any of the shafts both on strip down and rebuild.

I did have to tap the bearing cover on but that was it.

[philthehill]

The reverse idler shaft is a hand press fit into the casing. There should be absolutely no need to hammer anything.
If the shaft is worn and marked it could be difficult to remove and the removal process adjusted accordingly.
As above - do not do anything until you have the replacement shaft.