Popping out of 4th gear

[dumper]

Recently put together a AA and on road test the transmission popped out of 4th gear. Had the transmission apart and thought the gears all looked good. Did I miss something or would this be caused by something else? the other 3 gears run fine. Thanks

[tiredtruckrestorer]

In 4th gear you're coupling the main drive gear (input shaft) to the mainshaft. The 3rd/4th sliding gear moves front and slides over the main drive gear. Did you check the internal teeth of the 3rd/4th gear? How about the wear on the front of the mainshaft where the mainshaft pilot bearing rides. If you had it all apart, did you put the AA-7063 pilot bearing spacing washer on the front of the mainshaft? Often this get lost or forgotten.
Something has to be moving around or worn upfront to make it just out of gear. Another thought too, if the nose of the main drive gear shaft is worn and/or the bearing is bad that holds the front of the shaft in the flywheel, it could let the shaft move around and possibly pop it out of gear.

Keith

[dumper]

Keith, thanks for your reply. I will check your suggestions.