Matty; imagine my frustration, i use to have little knowledge of engine building and have thrown together numerous rebuilds over several decades with no issues. The more knowledge i get the more that seems to generate a fault.. grrrr!
Bill: yes quite right if any of this is to be of future benefit it would be useful to positively id parts. I’ll quote #’s from drawing supplied although as pointed out there are some differences from Comet installation but generally schematically the same.
So problem I had was without warning no 4th gear, stripped down and replaced 3658-52 gear change cam bush that has been shimmed out by PO, also selector fork pins 37939-52 although the signs of wear were negligible, also replaced output gear 3638-52 with a used item that appeared to have dogs in marginally better conditition. At this point I thought that all of latter may have been contributing to issue but having found that mainshaft output retaining nut 3089-33 was loose and oil seal garter setup 3636-52, 3635-52 was not firmly seated because the retaining circlip 3634-52 was not seated this was what i had thought was the culprit. I’d carried out a cursory inspection and was satisfied that the mainshaft bearing 3095-33 had not walked. Having reassembled all and satisfied that all gears engaged when rotating the rear wheel i thought all was well.
However, following approx’ 200 mls the issue manifested itself again, this time all i replaced was the outer bush 3659-52 to the gear selector camshaft 3736-52 and i had the bush made up 30 thou on internal flange length to negate end play that was in excess of 2 thou.
All gears selected on non running engine, within two shifts of shakedown run 4th had disappeared again.
Situation is i have dropped the box and am waiting for semi viscous fluid to drain, also for delivery of 52mm socket to loosen drive sprocket retaining nut 3089-33. Partly because i don’t want to over extend goodwill of friend who has lent me his 52mm socket and ratchet driver several times now.
Yes matty the indexing pawl was engaged and engaging, however oil seal garter setup 3636-52, 3635-52 was not seated because the retaining circlip 3634-52 was not seated, I don’t know if this occurred during dismantling or during operation.
Moving forward I intend to establish if the mainshft bearing 3095-33 has walked out, the actual engagement depth of dogs between 3642-52 and 3638-52 and if there are any cracks in the casing 3600-52 in the area of the bearing 3095-33 that I have missed as i have learnt this can occur.
Works actually contemplated are having spacer made up to place behind output gear 3638-52 to encourage better engagement of dogs and replacement for oil seal garter setup 3636-52, 3635-52 with a standard oil seal, at last inspection there was insufficient depth for Dragan off the shelf replacement which their site suggests maybe the case in some instances.
