860 jumps out of 3rd gear!

MO8N4ME · Feb 4, 2018

I have a '55 Ford 860 5 speed - Double Clutch. I bought it about 3 years ago and every once in a while it would jump out of 3rd gear. Sometimes on takeoff and sometime on deceleration it would just slip out of gear.

All the other gears all work good, 1 thru 5 and reverse, it is just 3rd gear.

The clutch went out of it yesterday when I was using the box blade, so as long as I have to split it I thought I would fix this 3rd gear problem. I'm hoping you guys are going to tell me it is in the shift forks and I won't have to tear the gear box apart. :?:

pomester · Feb 4, 2018

first thing to check is the detents - they are accessed by unscrewing a plug on the left side of the transmission - slotted head - underneath the plug is a spring and a "plunger" - both those pieces are still available - the plunger often shows wear and the spring can weaken - an appropriate sized o-ring can be used for sealing the plug when reassembling, gaskets are not serviced

Hopefully there's nothing inside the case that's causing your problem, that gets to be a big project pretty quickly -

here's a shift mechanism - this is 4-5, and had been modified by a previous owner but you can see how the spring and plunger interact with the mechanism to hold the transmission in gear

Dean · Feb 4, 2018

Quite common do to wear of transmission parts, most importantly shifting collar teeth. Most will jump out of gear or gears under an overhauling load. Third is the most likely due to it being used most often. The steeper the hill, the more likely it will jump out, and the more gears will likely be affected.

Replacing the detent plungers and springs will perhaps help but such is not the cause of the problem and doing so will likely not solve the problem. Still, doing so is easy and inexpensive so is worth doing. You may also wish to remove the top cover and inspect for loose, worn or damaged shifting forks.

If the symptom still exists after doing so, proper repair involves replacing the shifting collars and thrust washers to ensure proper bearing preload and proper engagement of the shifting collar teeth.

Most folks simply live with it.

Dean

Bern · Feb 4, 2018

Could be any number of things - worn detent notches in the shift rail, broken/worn detent spring, worn shift fork, worn shift coupler,
excessive component end play on the countershaft, etc. We can't tell you from where we sit - you'll need to open it up and take a look for
yourself.

My best guess would be worn teeth on the 3rd-reverse sliding coupling, since this is the connector that is used for shuttle shifting and sees
the most potential abuse. Resist the urge to shim up the detent spring pressure, since all that does is buys you a little time while wearing
out your shift fork.

MO8N4ME · Feb 4, 2018

(quoted from post at 11:34:18 02/04/18) first thing to check is the detents - they are accessed by unscrewing a plug on the left side of the transmission - slotted head - underneath the plug is a spring and a "plunger" - both those pieces are still available - the plunger often shows wear and the spring can weaken - an appropriate sized o-ring can be used for sealing the plug when reassembling, gaskets are not serviced

Hopefully there's nothing inside the case that's causing your problem, that gets to be a big project pretty quickly -

here's a shift mechanism - this is 4-5, and had been modified by a previous owner but you can see how the spring and plunger interact with the mechanism to hold the transmission in gear

Thanks so much for the replies. I'll pull the top cover when I split it for the clutch this week. When I first got the tractor about 3 years ago and pulled the top cover shifter plate. the gears all looked good at the time. I'm hoping it's the detent you speak of. I love the tractor, it's a real grunt horse for a 2wh drive.

Bern · Feb 4, 2018

I'm sure the gears themselves will look just fine. It's the clutching teeth that you need to focus on. Those are tough to evaluate without
disassembling.

MO8N4ME · Feb 4, 2018

I have worked around it for some time, but in doing grading or box blade where you might go 3rd / reverse, 3rd/reverse, a couple times, if it starts jumping out of gear it gets frustrating. Using a bush hog I use 2nd a lot and it avoids the problem altogether. Thanks for your input.

MO8N4ME · Feb 4, 2018

Thank you.

860 jumps out of 3rd gear!

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