M with Heisler od pops out of low side

IAJosh84 · Oct 16, 2011

I've been reading this site for about a year now and you guys are full of information and knowledge. I've been able to find answers to a lot of questions just by searching the site. I've come across a problem that I haven't been able to find much information on. I have a Farmall M with a Heisler 9 speed overdrive. It pops out of gears 1-4 and reverse when it's in low side. I haven't spent a ton of time looking into it yet was just seeing if there was anybody out there who has some knowledge about this. Thanks in advance.

Janicholson · Oct 16, 2011

Three primary reasons for gears jumping out of engagement. The first is wear from use and grinding them in to mesh such that the drive surfaces are tapered in a way that puts force on them toward jumping out. The second is failed detent balls and springs whos intent is to hold the components in place with location control, not direct force or pressure. When the springs rust and or break/fail, the controls can vibrate out of engagement. The third is shaft misalignment or bearing wear that walks the gears or dog clutches out of engagement.
If the linkage is improperly adjusted, the detent system will not be at the bottom of its rest notch. I hope this generic info helps. Jim

IAJosh84 · Oct 18, 2011

Thanks for your reply. I"m guessing that since this was a aftermarket add on that it"s possible that people don"t have a ton of experience with this. Looks like I will have to start with checking the linkage then go from there.

Janicholson · Oct 18, 2011

There is experience, but not too many pop out of gear. It seems that it might be unique enough to be difficult to diagnose. Jim

IAJosh84 · Oct 18, 2011

That's what I'm afraid of. It's been in the family since it was new and as far as anybody can remember the heisler od came on it from the dealership. It's had this problem for a long time we just always did light stuff with it that we could use the hi gears for like harrowing or raking. Since it just pops out of low side does that mean that it's likely something with the factory gears and not the heisler?

Janicholson · Oct 18, 2011

The heisler is going to be the cause. THe heisler runs the countershaft at a speed that provides the new ratios. In the lower gears, it also drives the countershaft (at the original speed) thus in either "gear" it uses the heisler. Parts may be hard to find, but if searched for can be had. If anything, it can be taken back to stock 5 speed with the removal of the heisler components and the replacement of those with the constant mesh input and countershaft gears from a donor tractor trans. Jim

D Slater · Oct 19, 2011

Two sets of gears for low and high range drive are in constant mesh. there's a sliding shift collar that locks one set of the gears (on gear ID) to the lower transmisssion shaft depending on the range shifted to. There's springs and popet balls to hold shift sleeve in place when shifted to ranges. Probably have to get in the transmission to see the problem. May be able to look in the belt pulley gear box opening to see if its shifting fulley into range.

mkirsch · Oct 19, 2011

Is the main gearshift lever popping out, or the heisler?

IAJosh84 · Oct 19, 2011

It's the heisler lever popping out. I can hold it in with my foot but that gets old after awhile. It does it in reverse too.

M with Heisler od pops out of low side

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