CT 335 HST Tranny problem

Shelby09 · May 25, 2017

Hi all- I have a CT335 with an HST transmission. I recently lost all but low range. The shift lever used to have notches for low, neutral, medium, neutral and high. It now moves smoothly from one notch to the next and again only has low range no matter what range it is in. Additionally, the tractor will move forward and backward when the pedals are pushed even though it says it is in neutral. The tractor has a little over 300 hours on it. I changed the hydraulic filters and the fluid is full. Anybody have an idea what is causing this?

the old grind · May 25, 2017

:welcome:

Sounds like something in your linkage came undone, not at the range selector end but alongside or inside the case. The detents might be in the handle, but it sounds like its just not leaving low 'down there'.

Follow the connection(s) and look for loose bits. Hopefully, you won't have to 'go inside'. t o g

Shelby09 · May 25, 2017

Thanks TOG. I'll look at that end this weekend. Also hoping it's not inside.

k0ua · May 25, 2017

Keep in mind this shift lever doesn't have anything to do with the hydrostat per se. It is just a simple 3 speed gear transmission that this lever operates. The hydrostat motor drives this gear transmission. The hydrostat pump supplies the flow to the hydro motor. The display on the instrument panel is driven by a variable resistor on the outside of the transmission connected to the lever. The varying voltage is fed to a module to drive the display. It doesn't really tell which gear the transmission is in, it only shows the position of the lever. Hopefully you have a simple mechanical connection problem that is not shifting the actual gears inside the gear portion of the transmission.

SSdoxie · May 27, 2017

Follow the shift linkage rod from lever back to where it connects to case. There is a bell crank that goes over the shaft going into the transmission. This bell crank is fastened to the shaft with at roll pin/drive pin. I have seen a few of these pins break, acts as a shear pin if excessive pressure is applied to shift lever when gears aren't aligned or in a bind.

Shelby09 · Jun 8, 2017

k0ua said:
Keep in mind this shift lever doesn't have anything to do with the hydrostat per se. It is just a simple 3 speed gear transmission that this lever operates. The hydrostat motor drives this gear transmission. The hydrostat pump supplies the flow to the hydro motor. The display on the instrument panel is driven by a variable resistor on the outside of the transmission connected to the lever. The varying voltage is fed to a module to drive the display. It doesn't really tell which gear the transmission is in, it only shows the position of the lever. Hopefully you have a simple mechanical connection problem that is not shifting the actual gears inside the gear portion of the transmission.

Thanks to all- I will give these ideas a try this weekend and see if this does the trick.

Shelby09 · Jun 12, 2017

Hey bros- the linkage shear pin was indeed broken. It was a real pain to get to but I was able to punch it out. Stuck a 16 penny hurricane hanger nail in it for temporary fix. I have mid range back but still no high range. May have to haul it in to get it looked at. Thanks for the tip SSdoxie.