remote shift extension vibrating loose

here is a new one for me - the remote gearshift extension keeps vibrating loose on our racer (3-rail, 4 speed). something is causing the vibrations to the point that all 4 bolts back off. the vibrations seem to be consistant through the gears, speed related of course. I’ve just pulled the box all apart and only things i find are a slighlty gawled up front spacer washer for the lay shaft and some slightly worn shift forks. there is a bit of metal grindings in the bottom of it. but the bearings and the input shaft slight wobble all seem good. any ideas?

coincidently or not i just installed a newly rebuilt motor that was balanced by a respectable builder, otherwise all else is the same.

I has a similar problem and it turned out to be the drive shaft u/joints causing the problem.

thanks- i suspected those and with the gearbox out tried finding any slack in the two u-joints but just by hand cant find any.

Is the layshaft press fit in the casing still good? - I have had problems with this wearing due to the high loads under racing condtions and the layshaft becoming loose.

cheers
Rohan

what kind of press fit should it be? it drops in there easy enough. is there and endplay measurement i can take?

The lay gear drops in and thrust washers at each end located it in fore / aft movement - the lay shaft it runs on, on needle roller bearings is a press fit into the casing. If this shaft loose in casing you can get problems

cheers
Rohan

to conclude - found the flywheel was way out of balance. My local shop had surfaced it for me and said it was still balanced good! This vibration, which i could feel, would shake the remote extension loose and the starter.