Hey all, new to the forums and am a new owner of a '99 F350 with a 7.3 and ZF6. Bought the truck cheap with a locked rear axle and after replacing that I found out 6th gear is unfortunately out. No grinding and the detent felt ok, but it just didn't engage.
A buddy and I pull the beast of a trans out and I got the rear cover off to do some investigation. Was hoping it was just the shift fork but it seems to be ok:
The countershaft gear did look a little funky, however:
Spoke with a friend who has quite a bit of automotive experience and he said the damaged detent ball could definitely affect shifting so I ordered a new main detent (the threaded plug) and plunger/ball assembly, hopefully this will be a <$100 fix!
a reman tranny is about 16-1700 on ebay with an exchange. Or, while you have it out and apart, bring it to a tranny shop and see what they can tell you for a repair cost, since most of the cost in estimating is the removal, which you already did