Hydrostat and braking

[Rotro]

On my 2018 1736, any hill that I brake to stop on, trying to go backwards always results in rolling forward until the brake is fully released. It's done this since day one. Doesn't matter how rev'd up I have it, the brake releases either too soon or the hydrostat doesn't engage soon enough. This weekend I grew sick of the problem after I wiped out a 4x4 post on the chicken coop trying to go backwards after dumping some feedbags.

I called the service dept and the tech isn't sure. He couldn't find any reason in the parts diagram why the hydrostat would ever be disengaged. He suspected there's a switch somewhere that disengages the hydrostat with the park brake lever but he doesn't see it.

A few moments ago, I thought about separating the brake pedals and only using left or right to see if that would at least bypass the problem. Haven't tried it yet. Perhaps that is how I am suppose to deal with hills.

Does anyone know what I am talking about and is there anything that needs fixing? I don't care if the hydrostat is always engaged as long as that means I won't roll down the hill a few feet before the hydrostat engages.

 

[Rotro]

Grok says the linkage off the pedal that goes to the floorboard activates a "neutral switch" and it's out of adjustment... going to go see if that's what's going on...

 

[Eagle1]

Hold brake, step on reverse it will start to move and release brake..... works for me. Little harder with the BX where brake and HST are on the same side. Normally us the loader to hold until it starts to move. Only an issue on steeper grades, I have plenty.

 

[Rotro]

Yeah that doesn't work for me. I can hold reverse all the way down reving the tractor and once enough brake is released, the tractor rolls until I have the brake pedal all the way out... then it jerks backward.

I think I see two microswitches behind the dash for the l/r brake pedal that probably are my problem, I just don't know if they can be adjusted yet if they are.

 

[Rotro]

My thought at the moment is that these switches suppose to be activated when the brakes are fully in, but whoever stuck them in had them activated until the brakes are fully out... just opposite of what they should be. I'm still researching.

 

[Rotro]

Took the dash off and figured out what's going on. Those two microswitches I saw earlier are only activated at the end of brake peddle retracted. If I try to adjust them to activate anywhere off parking, the arms will bend. It's almost as if they are the wrong switches or they are reversed and wired backwards.

As proof these things are my problem, I taped one always activated and this is my problem. Worked just like I think it should on a hill.

I'll study this some more but the only way I see to fix it to where these particular switches work correctly only in the parking brake position, is to get out my grinder. Surely that isn't the answer.

At this point, I am thinking of bypassing them and not have the hydrostat disengage ever. I don't know if I'll really ever need that.

 

[CalG]

I'm trying to think of a single situation where I would like to have the hydrostat disabled by the brakes.

Might save trying to drive with the brakes on, but that... I can tell.....;-)

 

[Dmacleo]

At this point, I am thinking of bypassing them and not have the hydrostat disengage ever. I don't know if I'll really ever need that.

could that possibly cause excessive wear?

 

[4570Man]

I'm trying to think of a single situation where I would like to have the hydrostat disabled by the brakes.

Might save trying to drive with the brakes on, but that... I can tell.....;-)

My forklift works that way. I’ve ran other forklifts that do the same thing. It’s designed so you can hold the brakes and rev the engine for more lifting speed without slipping the transmission but it is annoying if you’re driving on a hill. The forklift is not HST though. If it was you could just not push the drive pedal and accomplish the same goal.

 

[Rotro]

My forklift works that way. I’ve ran other forklifts that do the same thing. It’s designed so you can hold the brakes and rev the engine for more lifting speed without slipping the transmission but it is annoying if you’re driving on a hill. The forklift is not HST though. If it was you could just not push the drive pedal and accomplish the same goal.

That makes sense as to why those switches would be there but like you insinuate, I can and would just increase the throttle for more lift and not press the drive pedal. I put a wire-tie on activating each of them and drove all over to see if I was bypassing something else too. I don't detect anything even though there are 3 wires to each switch and not two. I don't know but it seems to work FANTASTIC now! What a relief.

 

[CalG]

That makes sense as to why those switches would be there but like you insinuate, I can and would just increase the throttle for more lift and not press the drive pedal. I put a wire-tie on activating each of them and drove all over to see if I was bypassing something else too. I don't detect anything even though there are 3 wires to each switch and not two. I don't know but it seems to work FANTASTIC now! What a relief.

Is this a case of a factory solution to a problem that doesn't exist?

 

[Rotro]

I'm convinced it is. Trying to simulate a fork lift I take it. The only thing I have outstanding is that there are three wires to each switch instead of two. Just guessing that if I had brake lights, the extra wire is for that. I don't so don't care... if something reveals itself, I'll update.

 

[lpakiz]

Caterpillar end loaders in the 1970s had this system. The foot throttle was to the extreme right, like your car. Adjacent to the foot throttle was an air brake petall, again like your car.
On the left side if the steering shaft was another foot brake petal. This left petal would apply brakes AND de-clutch the hydrostatic transmission.

To use this system efficiently, you would load the bucket, then back away from the pile or gravel bank, raising the load as you backed up. When you were far enough back, you would slip the shifter (located where the turn signal on your car is) into forward while engaging the LEFT petal, which de-clutched the transmission. Then you FLOORED the foot throttle to quickly raise the bucket up high to load a truck or dump up onto a pile.
When the bucket was almost high enough, you released the throttle petal and used the hydraulic pump load to quickly slow the engine to about an idle, and then released the left petal, which re-connected the transmission to the wheels. It became pretty automatic by day 2.
If you released the left brake with high RPMs, the loader lurched violently forward and soon the foreman would be standing on your ladder saying some bad words to you.

So I use this same system when I move snow or dirt with my 1754 Hydrostatic. When the bucket is full, step on BOTH brake petals to de-church the transmission. At the same time, mash the REVERSE petal to the floor to quickly raise the loader to the desired height. When the bucket is high enough, let off on the hydrostatic petal to bring RPM s down then release the brakes to re-engage the transmission. When engine RPMs are at a low level, press the Reverse Petal again to back up.

If you need to hold the tractor on a hill, slide your brake foot off of one brake petal, or only apply one brake as you stop. That will re-engage the hydrostatic transmission, and that will hold you on a hill. If you give the hydro too much feed, the unbraked tire will usually spin.
CONCLUSION: pressing only one brake petal will NOT de-clutch the transmission, but pressing BOTH brakes WILL de-clutch the transmission.

If you use the HAND throttle to maintain constant high RPMs, none of this is necessary.

 

[biffydog]

Took the dash off and figured out what's going on. Those two microswitches I saw earlier are only activated at the end of brake peddle retracted. If I try to adjust them to activate anywhere off parking, the arms will bend. It's almost as if they are the wrong switches or they are reversed and wired backwards.

As proof these things are my problem, I taped one always activated and this is my problem. Worked just like I think it should on a hill.

I'll study this some more but the only way I see to fix it to where these particular switches work correctly only in the parking brake position, is to get out my grinder. Surely that isn't the answer.

At this point, I am thinking of bypassing them and not have the hydrostat disengage ever. I don't know if I'll really ever need that.

I can think of a few instances where you might want the transmission disengaged while the brakes are engaged. If both brakes are engaged to facilitate a parking brake while utilizing the PTO for things like a 3 pt mounted chipper, buzz saw, irrigation pump, etc...things where the tractor is stationary (parking brake) and the engine is running at high rpm then you would want to have the transmission disengaged to prevent excessive heating of the transmission fluid and also cut down on fuel usage. I'd look into having the switches moved to the parking brake handle versus having them on the pedals / brake mechanism. That way, the only time the transmission would be disengaged is when the parking brake is on and not when both brake pedals are depressed.

 

[Chanceywd]

Maybe instead of a permanently disabling the switch you could figure out if it is NO or NC at that point. Then wire a momentary push button switch that would open or close the circuit when you needed it on a slope. This could engage the hydro circuit at that moment before releasing the brake and possibly keep you from overheating and damage to brakes or the hydro from defeating it altogether.

Bill

 

[jwmorris]

My forklift works that way. I’ve ran other forklifts that do the same thing. It’s designed so you can hold the brakes and rev the engine for more lifting speed without slipping the transmission but it is annoying if you’re driving on a hill.

Mine do too but they have 3 pedals, the center is brake w/out decouple from trans and the left is an "inching pedal" created just for the situation you describe.

 

[oldnslo]

What do the switches activate to disable the hydrostatic transmission and allow the tractor to free wheel? Is there some type of electric clutch between the engine and hydrostatic pump?

 

[Flogger]

I'm trying to think of a single situation where I would like to have the hydrostat disabled by the brakes.

Might save trying to drive with the brakes on, but that... I can tell.....;-)

Pretty sure if you have a loader you wouldn’t like it without a declutch. Put a bypass switch in it so you can shut it off.

 

[Flogger]

What do the switches activate to disable the hydrostatic transmission and allow the tractor to free wheel? Is there some type of electric clutch between the engine and hydrostatic pump?

Most operate a valve that returns the oil to tank. A second switch wired across the original would gib you the option of shutting of the declutch.

 

[Eagle1]

Pretty sure if you have a loader you wouldn’t like it without a declutch. Put a bypass switch in it so you can shut it off.

Neither of mine have a clutch or disengage. Lift off the petals and the tractor stops and does not move until you command it. I can put it neutral but never have. Pick a range and RPM and off you go, and I do mostly loader work on slopes or tight quarters. Only goes into neutral if I need to tow it or coast it down a hill because of a problem.