revers lockup

[larson coulee boy]

My 300 (1020) in reverse while backing slightly up hill will lockup the drive train and kill the engine. After I force the transmission into neutral all is normal again until I back up. I have the differential out and have inspected all the transmission components and all looks like new. All the shifter shafts and forks are excellent and tight. The brake disks are new and new piston seals installed. The tractor has less than 4000 hours.
My local JD dealer technicians with many years of experience are baffled.
Can anyone please help me?
Thank you very much in advance!!
Don

 

[JD Seller]

Check the bearing cages. I have seen a roller bearing wear the separator cage out and then the rollers would cam lock in one direction. Also have you checked the end play on the shafts with a dial indicator. Just "looking" at them is not really good enough. If the end play is too much they can bind too. Not commonly but they can. The gear mesh is too far out of line. The gears can climb/bind.

The fact that it is only doing it in reverse tells me that it is a end trust issue. The angle on the reverse gear coupled with the torque, pushes the transmission shafts the opposite directions than when going forward. So it just about has to be a bearing issue.