HST pedal sticks under load

[tc35dforme]

Jtn, Is there a typo in your post ?? You reference FASTER in two separate sentences apparently outlining two separate modes of operation. Can you break it down a bit or am I just missing something on this one ???

I may regret this....but......doesn't the 'power' and 'speed' run on an inverse relationship. I was under the impression that the maximum 'power' ( traction assumed to be 100 % ) was obtained at the beginning of the pedal stroke. As you squash the pedal, you go faster, but you give up traction force or 'power'.

I find that when I'm really trying to push something...a slight nudge of the pedal to a creep seems to do the trick.

I defintely don't know the physics behind the hydro transmission, but I do know that if I'm in Hi range - "bunny" and slam down the pedal...the tractor isn't too happy.

I guess some time reading the repair book is in order. It never hurts to learn....or ask questions.

 

[RocketJSquirrel]

I wonder if this is a long time Ford/NH problem. Our 1995 Ford 1320 does the same thing. OTOH my JD 755 stops immediately when you let off the pedal. I'll check out the spring tension.

 

[DK35vince]

tc35dforme,
Your version on how hydro works is more accurate.

 

[jtn]

There are two ways to go FASTER with a hydro tranny. First is to INCREASE the displacement of the PUMP (depress the travel petal all the way); the second way to go FASTER is to DECREASE the displacement of the MOTOR (shift to rabbit mode). The gear shift lever on the right side has no effect on the hydro; it is a two speed transfer case (you are right, if this is shifted into high range you will get less power to the ground).

The hydro tranny will have the most power when the pump and motor are both at maximum displacement. This is turtle mode with the travel petal floored. With a hydro tranny you are increasing tractive effort and speed until the pump is at maximum displacement. I agree this does not seem to make sense unless you understand the workings of the hydro system. If you shift to rabbit mode or high range with the transfer case this will decrease your tractive effort and cause you to go faster.

I will see if I can get some diagrams or more info on the web to try and make this a little more clear for anyone interested.

JT

 

[jinman]

I think you are correct on your description of what happens with our tractors. JTN's description of added power is only true if you have unlimited torque from the engine. If you change the angle of the pump swashplate in any range, you will only increase the tractive power up to the limits of input power. Pressing the pedal further will cause the engine to lug down and stall unless the relief valve's pressure is exceeded.

 

[jlong]

Hope you tried the "quick fix" of lubing the roller and tightening the spring because it worked great for me. My TC35D has acted the same since I got it. Now with 275 hours on it, and two trips to the dealer, who explained it as "Characteristics of a Hydrostatic tractor", I tried it and it worked. I was a bit skeptical since my adjustment spring was all but 1/2" from the tightest setting, but I tightened it all the way and sprayed some silicone on the roller. Immediately tried it on a slope that always caused the tractor to keep going in low, and the tractor stopped on a dime.

Good luck. Hope it works as well for you.

And again, thanks to all of the knowledgeable people on this website

 

[djradz]

I'd suggest something a little heavier than silicone spray, like 30w, but anything is better than dry for the roller.

 

[tpaulson]

Just a quick update. I adjusted the return spring tension almost all the way to the end of the threads. When I got the tractor the spring was already set about a 1/2" away from the end. I made this adjustment about a month ago and have not had the pedal stick since.

Thanks for everyone's help and suggestions.
Tim

 

[Mosey]

tpaulson - After you tightened up the tension on the spring, did it make it noticeably harder to push the pedal?

 

[tpaulson]

Mosey
It may have made the pedals slightly harder to push, but I don't think it is very noticable.

I am not sure if your TC29 would have the same type of tensioning spring to adjust.

Tim