Cub Cadet 127 transmission failure

[brother]

My Cub Cadet 127 hydrostatic transmission went completely out.

Last fall I bought a Cub Cadet 127 from the original owner (I think it was built around 1971). The original owner took good care of the tractor. This is my first tractor. The other day while mowing the grass, as I quickly shifted from forward to reverse and back to forward again, the transmission suddenly stopped working. There was no unusual noise.

The transmission will not operate in forward or reverse … no movement whatsoever.

I confirmed that all the linkages are working from the shift lever on the console back to the trunnion on the transmission, that the transmission is full of oil, that the two release valves on top of the transmission are not stuck, that the oil in the transmission is the correct color with no burnt smell, and that after jacking the rear wheels off the ground the transmission still will not work. I did notice that oil soaked grass was accumulated all around the top of the transmission and the cooling fins but noticed no signs of excessive heat.

The only symptoms I noticed before the failure was that the tractor would speed up slightly when I went down a slight grade and/or after I completed a tight radius turn. The tractor pulled good when I drove up that same slight grade.

I did confirm that the drive shaft from the engine was rotating the coupler at the input side of the transmission but the output side of the shaft was not spinning (the output shaft is located at the top rear of the transmission and protrudes about an inch out of the finned casing). I was able to turn that protruding output shaft by hand (I felt nothing unusual and it turned smoothly).

I have not yet tried replacing the transmission filter.

Any ideas of what to do next besides splitting the tractor and opening up the transmission?

Is there a way to perform a pressure test? I do not want to remove the transmission if I can do a pressure test before I split the tractor.

This is my first post to this forum.

Thanks for your help!

[Sam Mac]

Sounds like the spirol pin that connects the coupler to the pump shaft broke since the shaft is not turning on the back side of the pump. Take a good look at the coupler and see if it's spinning on the shaft going into the pump.

[Methos]

Thanks for all the info!

These are not known for just giving out and I think Sam has you on the right path.

[TheSaturnV]

Ditto on the spirol pin. Hydros not known for abrupt, catastrophic failure.

[Yamaguy]

I had that happen to my 147 last year. It was the spirol pin where the driveshaft connects to the engine. I bet that is the problem.

[brother]

Thanks you guys!

I am VERY grateful for your replies ... I will look at the coupling tonight and report back, hopefully ASAP.

I have only owned this tractor for a few months and I am already experiencing the Cub Cadet "bug".

[TheSaturnV]

While you're looking in there, have a close gander at the coupling that the spirol pin engages. Over time the pin wears out a groove in the coupling, creating enough gap to allow the pin to slap forward and back. This is typically what breaks the pin. Warrants a weld job or replacement of the coupling.

[Sam Mac]

Originally Posted by TheSaturnV

While you're looking in there, have a close gander at the coupling that the spirol pin engages. Over time the pin wears out a groove in the coupling, creating enough gap to allow the pin to slap forward and back. This is typically what breaks the pin. Warrants a weld job or replacement of the coupling.

Also check out the complete drive shaft, rag joints, look for wear at the ends where the shaft sits in the ball socket. Matt G knows more about this style drive line than I do so you may want to check with him.

[brother]

The problem is, in fact, that the spirol pin is missing.

I searched for a part number on the web but could not find one for my Cub Cadet 127. I searched this forum and found some posts that lead me to suspect that the pin is a stainless steel "coiled spring" pin that can be purchased in a bulk bag of 25 pins from McMaster-Carr at

http://www.mcmaster.com/#standard-spring-pins/=hkcse7

However, I do not know the correct McMaster-Carr part number (e.g., diameter and length and if I should get the extra strength ones).
I would prefer to purchase pins from a sponsor or someone affiliated with this forum or a local dealer in my area if available.

Does anybody know the part number, size and/or where I can buy a pin?

I took some photos of my tractor before and after I worked on it this evening and will try to post them with a bit of narrative after I cut my grass with my push mower tonight … probably will not be able to post until tomorrow.

In due course, I will reply to the other great suggestions you guys have given me about other potential problems to look for.

Again, I am so very grateful for the help you guys have been giving me.

[brother]

Attached are 4 photos of my tractor before I started working on the transmission.