“Here we go again” 1275GT project NOW FOR SALE

[Dearg1275]

Pressing on with the gearbox. Checking slowly through the bits it was disappointing to find the baulk ring surfaces of the gears in this state.

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What causes the coating to become mottled and pitted?

I decide to reject 1st, 2nd & 3rd gears on this count. Luckily the 1st motion shaft should be OK. A rummage through my boxes of used kit came up with some half decent replacements and usable selector forks.

I did trial build with the old bearings to check function and find any wear faults before committing to new kit. Using old stuff at this stage reduces the chance of damage to new parts if multiple strip downs are needed to get things right. I also like to be able to see what is going on with the selector crab so arranged this. The remote gets bolted on too. That way you get a true feel of how the box is behaving and it highlights areas of wear well. This showed that the suspected wear on the bronze bushes in the diff case was quite extreme. You could see the rod bobbing about side to side. Not so easily appreciated if you are pushing it manually or bopping it with a soft hammer.

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Lots of wear in this box the diff housing is toast.

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D

[Jason]

The moly coating degrades from prolonged periods sat in old multigrade. I have come across this alot over the years. There is a transmission company near to me that will recoat gear cones with a new molybdenum coating if you ever get stuck. I have plenty of A Series gears/close ratio sets/gearboxes/parts if you are ever stuck....
Keep up the great work....
J

[Jason]

The diff cages pre A+ are generally scored as the one from your box. The later A+ ones do not suffer from this as the bronze thrusts are 'tabbed' to stop them spinning and causing the wear shown in your picture.

[Dearg1275]

The diff cages pre A+ are generally scored as the one from your box. The later A+ ones do not suffer from this as the bronze thrusts are 'tabbed' to stop them spinning and causing the wear shown in your picture.

Yes I have used up my supply of A+ Diff housings replacing the likes of this and modified good A type ones to take the later tabbed thrusts.

Have you used the company that reconditions the synchro cones?

D

[Jason]

Yes I have used them in the past:
http://www.beagleengineering.co.uk/

Beagle engineering carried out the development work for the 5 speed components for the rod boxes. They can reverse engineer gears and redcoat existing gears, not a cheap process for one off’s - but better than using cheap aftermarket gears. Send me a PM if you need contact details.
J

[Dearg1275]

I decided to push the boat out and try having the gearbox bits vapour blasted for the first time. The result rather wowed me.

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While I wait for various bearings to turn up I amused myself with making a simple bracket that should make one gearbox task easier and more reliable.

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D

[rolesyboy]

I’ve started having my gearboxes vapour blasted. Takes a lot of tedious cleaning out of the equation and the results are ace. Seemed criminal to paint the case but beats trying to clean all the crap off the exterior find and odd shapes

[Andrew1967]

Vapour blasting is awesome on ally.

Just a shame my mate sold all his gear last year as I wont get any future stuff done as cheap.

[251 ENG]

Vapour Blasting is a fantastic cleaning process , BUT you need to be sure you get all of the glass bead residue off afterwards.

[Dearg1275]

Vapour Blasting is a fantastic cleaning process , BUT you need to be sure you get all of the glass bead residue off afterwards.

Oh yes indeed. I spent a long time making sure it was all gone. A good scrub in hot soapy water in the kitchen sink to stat with. Getting threaded areas clean again was the most troublesome. Little bottle brushes and compressed air many times, try a bolt and do it all again. Still it’s probably worth the effort. It also supports the local economy.

D

[rolesyboy]

Agreed re the need to remove medium and get scrupulously clean. Probably worth leaving some bolts in the threaded holes where practical??
I instruct my chap to focus on the exterior and avoid bearing faces which he seems happy to do.
Wonderful results and so much nicer than doing by hand

[Peter Laidler]

We had a rule of thumb in our big workshops, backed up by a big humorous sign in the sand and bead-cleaning bay to the effect that '.....no unprotected threaded or blind holes allowed within 1 mile of this bay...' The blast mediums were the death knell of threaded and blind holes so far as we were converned. Especially the small BA ones used in delicate instruments and small-arms

[Dearg1275]

Back to the nitty gritty (nothing to do with blasting grit). The diff bearings were very much worn and had to go. But how to get them out. Tap them, screw in a large bolt and use a slide hammer or knock them out from behind? All that involved acquiring such items. Too much hassle.

An old diff out put shaft was cut down removing the splined portion. The bush was ground back until bits of steel showed (probably wasn’t necessary) and one was welded to the other. A few gentle taps with a hammer and the bush was out.

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The same procedure for the diff cage and then just a matter of choosing the right sized sockets to push the new bushes in using the vice. For the crown wheel I had to devise a long bolt and various stout washers as the vice was not deep enough.

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I just have to acquire a suitable reamer now to finish the bushes.

Oh and yes a friend did come up with a decent diff cage.

D

[Jason]

Not often you see an A Series non tabbed diff cage with no scoring on the machined face for the bronze thrust

[Dearg1275]

Surely this is what boiler cupboards were made for?

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I’m trying a paint from Lechler LS443. I dries to a semi gloss. Applies direct to metal and has anti-corrosion additives. It goes on nicely too. The down side is it takes a long time to go off.

D

[Peter Laidler]

Always taught that taking a long time to go off/dry/cure was a GOOD sign. Indicative of hardness.

I bet we're all trying to identify the parts.......

[Dearg1275]

“Tales of the unexpected”. I was all content steadily building the gearbox all ready to drop the central oil pick up into place when I came on a no entry sign!

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I was very glad that I had a nice clean box so that I could keep track of the debris as I carefully knock out the aluminium casting flash. Double sided adhesive tape was useful in retrieving the bits. It would have been easier if they had been suddenly magnetic.

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All’s well that ends well.

D

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[Dearg1275]

With the gearbox all sorted and tucked up in wrap for when it is needed, my attention turned to that grotty servo. The shells were completely beyond salvage with corrosion right the way through. I managed to pick up a disassembled unit of the correct vintage and had the shells re-plated after they had been vapour blasted. I also had a larger version of a later type Lockheed servo that was new old stock. The original plating is a paler colour when compared with the new plating.

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My thought was that between the three units one good one might emerge. First off was the piston rod. I guessed they would be the same. The two old rods did have marks on them but the one from the large unit was PERFECT!

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The kit of bits was comprehensive and, if you need them, the build instructions are extremely detailed and clear. The air val piston and the main seal carrier are now both in stainless steel and provided in the kit.

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All sorts of “new” bits were raided from the NOS donor including the air valve assembly and air non return valve. That finished things off nicely.

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If anyone reading this is short of any bits or can use the big shells let me know before it all goes to the skip.

D

[rolesyboy]

Hi, message sent re servo. Thanks. Mark

[Dearg1275]

Today I was able to get the GT into the work shed. I managed to persuade a neighbouring crofter that their barn would benefit from having another mini in it so freeing up room. That what barns are for apparently.

A bit of a shuffle round with the wee tractor and the GT was delivered to it new home for a while.

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It was of course then completely necessary to remove the drivers door and bonnet to have a poke about and discover lots of interesting horrors.

Continued