Gearbox rebuild – take 2

I rebuilt my gearbox around 1986 in my college dorm room. Cleaned everything at home during winter break, then brought all the parts back and assembled it with a hammer and screwdriver (as far as I can remember)  – the layshaft and needle bearings went bad and took the laygear with them.

I thought that the gearbox was fine, but as I washed out the tailshaft housing I saw shiny specs – not just gold (brass) but silver (steel) – then I remembered that my gearbox was making some noise back in 1992 but seemed to work fine.

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Disassembly was fairly straight forward until I got the mainshaft out, then I found some damage – pieces of washer inside:

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And then the mainshaft came out and I found this almost destroyed thrust washer:

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Sorry about the blurry picture, but the above shows the little bit of thrust washer left in the groove – from 5 o’clock to 8 o’clock – the rest is of it was in the bottom of the case and makes the jigsaw of pieces above.

The cause of all this was the infamous 2nd gear tophat bushing – it should be one piece resembling a top hat, but this is what i found:

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More shiny particles as I cleaned all the parts:

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Finally time to reassemble – the housing is nicely glass beaded and washed:

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The top of the housing was drilled for a vent hole – later gearboxes had this – earlier ones didn’t many suspect it is there to relieve pressure and thus prevent leaks at other places. While I rebuilt the top cover, it was easy to drill the hole and clean up:

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Time to replace the bearings in the layshaft – the shaft was bought from TRF 20+ years ago and was supposed to be hardened. It looked good so I kept it, but with all the metal shavings, I didn’t want to reuse any bearings. Kai @ wishbone classics has some caged needle bearings that are longer and the cage also gives a harder wearing surface so these went in – old bearings below – notice the spacing of the needles:

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New bearings – caged and more needles

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Easy press fit, and due to the length, they don’t need the spacers or circlips.

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Time to assemble the mainshaft, but first you have to figure out thrust washers needed by doing a dry assembly and measuring endfloat- I did both sides at one time, but Bentley and Haynes call them out as different excercises – each stack on each side of center gets measure seperately. The stack on the right is retained by one earless circlip – I cut the old one in half and used it for test fits.The right hand stack also has a 2 piece steel top hat bush. All the bushes on the mainshaft are now steel

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The stack on the left above is held in place by the pressed on rear bearing – no one wants to press this on and off as they test thrust washers and take measurements – Kai suggested I cut the center out of an old bearing and hone it to be a slip fit. I did this – I had previously done it for rear wheel bearings and it works great.

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If you rip the metal strip out of the middle that keeps the bearings space, they can all roll to one side, and the center ring pushes right out.

As I was doing endfloat on the shaft, I was also checking float of bushings on gears. That is when I found 2nd speed gear was affected by the bad 2nd speed bushing – notice the ridge – the destroyed thrust washer above from the broken bush, peened the edge of the gear over and the bushing would not slide all the way through:

2nd-gear-ridge

 

Kai came through again and found me a used 2nd gear that looked new.

All new bearings, all new bushings, new springs in the gears, new syncro rings that were beefier then the old ones:

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Finally onto the bell housing and new bushings for the cross shaft – old versus new below more then 2x longer:

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And then the dreaded fork – I honed the hole with a tapered punch and sand paper as i wanted to make sure that the pin went through and into the other side:

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Then I drilled for a roll pin

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Installed the roll pin and tie wire:

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Clutch and pressure plate ready after pulling them twice. Once because someone on the 6-pack forum noticed a rivet missing in the clutch disk, second time when I read that Haynes manual was wrong on torque numbers for flywheel.

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I got really good and yanking the gearbox and putting it back, but there is no car body in the way:

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A great big thanks goes to Kai at Wishbone classics for good advice and getting me parts quickly, at a good price and with reasonable shipping costs.

www.wishboneclassics.com