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Old 09-29-2013, 02:56 AM   #1404
Box'a'bits OP
In need of repair
 
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Joined: Sep 2008
Location: Wellington, New Zealand
Oddometer: 2,005
Gearbox recon - part five

Notes on gearbox while I remember.

I didn’t disassemble the input shaft – I didn’t have anyway of relieving the spring pressure on the circlip. Maybe next time. As a result, I haven’t replaced the input shaft roller bearing & bush. The bush has some marks from the prior seal. The bearing has quite a bit less movement than the corresponding bearing that came out of the RS. Next time maybe.

The little input shaft pushrod seal is a truly trying little piece of German engineering. I needed to pull the input shaft output side bush off the shaft to allow me to punch this through & out of the back of the bush. Then I reassembled the seal into the bush from the rear, pushed it through to the front, & then pressed the bush back onto the shaft. The corresponding bearing got a nice new baffle on the input side, given I’d munted that getting the old bearing off.

The layshaft bearings were replaced. I used the bearing splitter on one as there was not clearance between the bearing & the nearest gear.

As much as I would have liked a lower 1st, I was too cheap to buy this & the shaft would have required a big press to remove & replace this. Likewise the higher fifth (though this was less attractive for me).

I heated the bearings in hot oil, & froze the shafts. I still needed to ‘persuade’ the bearings to go on.





I put a spring clip under the circlip, to allow for the radius in the input side output shaft bearing. Nice & tight. Hopefully won't move.



Parts diagram courtesy of Max BMW. I had to reassemble the output shaft twice. I put a washer in the wrong place, noted some slop on the middle gear (11 above). I realized my mistake, & had to pull the output side bearing again to correct this.

I haven't replaced the selector forks, or the bronze bush (14 above) that was showing some marking.

To reassemble the gearbox, the layshaft, output shaft, & one gear selector needed to be repositioned in the gearbox as one assembly. The other 2 selector forks could be installed after the event because the shaft they moved on was able to be removed. I had to push the layshaft & output shaft into the gearbox three times. The first time the shaft slid in fairly nicely, but I realized too late that I hadn’t put in the one selector on the immoveable shaft. Consequently I had to reheat the gearbox case end in order to release the gear shafts again. The second time the gearbox wasn’t hot enough (I was rushing), & the bearing hung up in the case. The third time I heated the box longer & hotter (150 degrees in Mandy’s oven – but the case was spotless your honor). Perfect. I'll add more photos tomorrow. And I'll start to look at the shimming.
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Box'a'bits screwed with this post 09-29-2013 at 03:13 AM
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