Cub Cadet 129 hydrastatic questions
 

I have a 1974 cub cadet 129 hydrostatic. This is my first hydrostatic cub cadet. Now i have heard that you aren't suppose to be able to move the tractor when its off, but it rolls freely. Another thing is it doesn't stay at a set speed, it likes to either go slow and stop or go faster until it hits full speed. I don't know if this is what its suppose to do, but if it isn't id like to know if there is any way to fix this.

You may be able to roll the tractor because someone put in auto relief valves. Someone will correct me if I'm wrong, but if you pull the tunnel cover off and the relief valves are flush on top they are auto relief. If there are little pins sticking out the top they are manual valves and may be sticking allowing you to roll it. Spray penetrant on the valves and work the pins to free them up.

When it speeds up and slows down, is the control lever moving also? If it is, there should be a nut in the dash tower you can snug up to keep it in place. If the handle is not moving you need to do some trunion repair.


http://cubfaq.com/trunionrepair.html

Bill

Bill is on the right track. I am thinking your trunion is worn.

Both the other guys are on track. I will add that if the lever moves on it's own, there is a friction nut on the hydro lever that "holds" it in place. Sounds like it may need tightened.

As to the friction nut, somewhere along the way, cub changed from a design that used a pinch bolt around the lower bushing to the design with the friction washer and the nut. I'm not sure when they changed, but it was after 1972. Yours may have the older design with the pinch bolt that may need to be tightened a little. Cub says in their parts look-up to update the older design with the newer design if parts are needed, so yours well could have been updated. I would appreciate if someone would clue me in as to when that change took place.

The parts book gives the SN# break for the change....... 425999

Ryder pm'd me more questions and I told him I would post them here so he would get better answers than I can give.


I don't know much more about relief valves than in my first post. I've never had an issue with the ones in my 1450.

If the handles moves, the friction nut/pinch bolt needs to be tightened, a couple other guys responded with better detail than me. Maybe someone has a picture of it to guide you.

The replace the fluid, you need to pull the rear cover off and drain and clean out the diff housing. Fluid is filled through the plug on the rear plate. I believe it takes just over 2 gallons of hytran to fill it.

Bill

About 7 quarts oil to fill tranny/diff/hydro.

Somebody correct me if I'm wrong, but I'm under the impression that the auto valves will dump automatically when shut down your tractor. However, if you have the manual valves, like I do, you have to push down on the top of the valves to get the tractor to move.

I'm fairly new to these machines as well. But I would look close at all your linkage for the hydro. The trunnion probably needs addressed. Also, there's a cheap little bushing that fits inside the shaft at the bottom of the hydro lever where it connects to another piece, mine was shot and until I fixed that little bugger I couldn't keep a constant speed no matter what I did.

Good luck!