Erratic mowing speed-hydro tractor

[sawdustdad]

Originally Posted by Sam Mac

It is part of the Hydro deal get used to it or get a gear drive. I run with one hand on the hydro all the time.

Of course I've been mowing for 35 years with my 108. So that's what I am used to with my Cub. My blue tractor is gear drive. My orange is hydro. It has two ranges, high and low. In low range, I mow at "full speed" which is just about right for mowing, so I'm not constantly adjusting the hydro and it maintains a constant speed. As a matter of fact, the hydro on the orange tractor maintains speed up or down hill pretty well for any given hydro setting (foot pedal position).

I've ordered a couple new relief valves. Will have to look at the trunnion on this 1650 and compare operation to the 1450 where I fixed the trunnion.

[R Bedell]

I really like Cub Cadets, but, a hydro will fail on a grade.

NONE of my Cub Cadet hydro's fail on any grade.

[CADplans]

Originally Posted by R Bedell

NONE of my Cub Cadet hydro's fail on any grade.

Roland, can you show us a pic of the grade?

Funny that a dealer can not sell me a new one that works!?

[dale c.]

check the trunion for wear [as mentioned] if there is much clearance [loosness]in the big spring you need to shim it up with 1/4"flat washers to take the play out 1 washer on each side should be lots if you get it too tight it will make the hydro touchy[jerky] ,also the side of the trunion usually is worn[depending on hours on tractor]that will need fixed while your in there too,as far as not backing up hills there is only about 1/3 the travel compared to forward so with play in linkage they don't back up as well

[ajcombs]

Originally Posted by R Bedell

NONE of my Cub Cadet hydro's fail on any grade.

I'm thinking what he meant is fails at staying at a constant speed without adjustment. As i have a hill at my property that they have no problem mowing up but you have to adjust to go up or down and just to let you understand how steep it is the gear drives speed up going down and i fear overrev of the engine, i love both and have used both gear drive and hydro of several brands and the gear drives are more consistent but will speed up going down the slope as well.

I love mowing with the hydro bc of the ease of changing direction.

[Yosemite Sam]

Contrary to popular belief, a hydrostatic transmission is not a cruse control. Just as with anything else hydraulicly operated, more resistance requires more movement of the lever.

[macman81]

Originally Posted by R Bedell

NONE of my Cub Cadet hydro's fail on any grade.

I agree. If you spend the time necessary to go through all the linkage and trunion and repair it to "new" specs, you will very very little speed change on a hill. It may change speed a very small amount due to the springs being compressed, but you should not have to constantly adjust your hydro lever to keep a steady speed. many prefer to just "get used to it" rather than tear the whole tractor apart.

[sawdustdad]

Originally Posted by macman81

I agree. If you spend the time necessary to go through all the linkage and trunion and repair it to "new" specs, you will very very little speed change on a hill. It may change speed a very small amount due to the springs being compressed, but you should not have to constantly adjust your hydro lever to keep a steady speed. many prefer to just "get used to it" rather than tear the whole tractor apart.

This is my understanding as well for a hydrostatic transmission--it is, after all, a positive displacement pump, right? Your engine throttle (governor) will adjust fuel to compensate for changes in load, but the the hydro pump should keep on pumping, regardless of grade. This is my experience with my orange tractor.

For my issue (slow/no reverse, especially up a grade) I am betting ($200) that it is relief valves. Besides these, which components need to be looked at to bring things back in spec? Assuming the trunnion is repaired, and the brake is adjusted properly, and the hydro lever stays where it is put, what else should be investigated?

[sawdustdad]

Originally Posted by Yosemite Sam

Contrary to popular belief, a hydrostatic transmission is not a cruse control. Just as with anything else hydraulicly operated, more resistance requires more movement of the lever.

I don't think this is correct. While I agree it's not cruise control, as it doesn't measure and adjust ground speed, it's a positive displacement pump. At least it is supposed to be. I suppose if worn out, it isn't so "positive" any more. That may be the problem. But you can't extend that reasoning to "anything hydraulically operated" as that's a stretch.

[Sam Mac]

Every hydro that I have used will slow down going up a hill and speed up going down the hill, some more than others. The BX when in low range seems to be the best but if the hill is steep enough it will also require adjustment.