Ford 1120 jumps out of medium range

[BJW43]

I have a 1990 Ford 1120 that will not stay in Medium range. Low and High range work fine but Medium (my most frequently used range) jumps out of gear and into neutral. It starts out fine and then jumps out. There is no grinding noise, it acts more like a detent problem. Any help is much appreciated.

 

[Harry in Ky]

If it acts like a detent problem it should feel like detent problem. If it feels right(as compared to all other shifts) then it's more likely a gear problem. I believe this is a sliding gear transmission, and since it's range gears involved, it's probably in the rear main housing. Detent springs/balls are probably not accessable from the outside. I suspect if you drain the oil from the rear housing and go "fishing" you may find some broken gear teeth/chunks in there somewhere. I think if you remove the lift housing and shift your lever in and out of the affected range you may well see just what the problem is.

 

[BJW43]

If it acts like a detent problem it should feel like detent problem. If it feels right(as compared to all other shifts) then it's more likely a gear problem. I believe this is a sliding gear transmission, and since it's range gears involved, it's probably in the rear main housing. Detent springs/balls are probably not accessable from the outside. I suspect if you drain the oil from the rear housing and go "fishing" you may find some broken gear teeth/chunks in there somewhere. I think if you remove the lift housing and shift your lever in and out of the affected range you may well see just what the problem is.

Thank you, that gives me a direction to start. You described it perfectly when you indicated that it acts like a detent problem but it doesn't feel like one. I fear you are correct in suggesting a broken gear. I've never worked on transmissions so this will be a new experience for me. I just finished flushing the cooling system and replacing a head gasket and water pump so I may as well go "all in" and give the transmission a try. It will be a couple weeks before I can get to it, but I'll definitely take a look.