Gearbox shimming....help!

[alanscottj]

Having a right mare trying to shim a gearbox. I have had everything out and all looks ok, but, when I try to shim the first gear the gap is huge, even with my biggest shim (2.89) the gap is bigger than my biggest feeler (0.9). The layshaft is just proud of the first gear, tried another layshaft and that was flush so scrapped that one.

Any thoughts?

[dave wheeler]

which gearbox is it? i believe li150 box`s can have shimming issues with certain case and layshaft combinations

[alanscottj]

which gearbox is it? i believe li150 box`s can have shimming issues with certain case and layshaft combinations

GP200 box

[wack 63]

The gears need to be higher than the layshaft. Either the layshaft 4 th gear stop is worn or perhaps the gears, especially forth gear. If you know someone with a lathe you can have the flush layshaft skimmed a tad so the gears fit higher or source some more gears and layshaft to try, sometimes just one gear cog can remedy your problem.

[alanscottj]

Boy do I feel a pleb! Spent hours trying different combinations of layshaft, gears, shims etc etc, only to suddenly realise that I have been measuring it wrong all day. I have been measuring the initial gap between endplate and shim, not sliding it right in to measure between race housing. As soon as I realised, took out the far too big shim and put a slightly smaller one in, and pushed the feeler right in, it slid under the endplate giving me a clearance of 0.20

[Strummer10]

Interestingly I re-built a mate's LI 175 in the summer and the layshaft was proud of the first gear ( when we benched it) and had scored about a 0.5mm groove into the shim , where it had been constantly rubbing on it over the 12 years since the initial build he had done by someone else and told me it run trouble free ??

[wack 63]

Sorry to say but you should be measuring between the shim and the raised ring cast around the bush on the endplate.

[alanscottj]

Sorry to say but you should be measuring between the shim and the raised ring cast around the bush on the endplate.

That's where I'm measuring now, I think I referred to it as the race housing I'm pretty sure I have it shimmed correctly now

[wack 63]

Phew