relief valve question

Wed Jan 25, 2006 6:15 pm

I have always wondered why earlier Cub Cadet hydros such as the 107's, 125's, 129's and the like all have the small lever on the right side of the tunnel cover. The 782's however lack this small lever to relieve the hydro pressure. What is the reason for this? Are the relief valves in the 782 different than in the earlier cubs such as the 107? As in... do they self dump and are they interchangeable between models? I've always wondered this, but never really asked why. Thanks.

Wed Jan 25, 2006 8:59 pm

You answered one of your own questions.....LOL

If there is a lever of the side of the tunnel, then it has manually dumped valves, and the lever must be 'raised' in order to push the tractor....a lot of times on the NF's the 'flapper' that pushes down the relief pins is broken/missing, and even though the lever is raised, the tractor won't roll.

If there is no lever, then the tractor has self dumping valves.

Since the valves simply thread in, I would say that a person could swap a set of self dumping valves in place of the manual valves....

All of my hydros have self dumping valves, and have never tried swapping valves, so it is possible I'm wrong.

Wed Jan 25, 2006 11:09 pm

The valves will interchange, but you don't want to put the earlier manual valves in a tractor not equipped with the dump lever. You also don't want to have to buy one. :cry: Pricey.

Wed Jan 25, 2006 11:09 pm

My 1282 has two self-dumping valves in the top of the trans. One of them leaks like crazy once the pressure builds up. Anybody have a spare they would consider selling?

Wed Jan 25, 2006 11:09 pm

Thank you for the info. I really wanted to get an answer to this as I am currently taking the pump out of a 129 and installing it in a 107 along with the hydraulic lift. However, on the 129 pump there is a bolt in front of the relief valves... some sort of pressure adjustment I guess that hits the "Flapper" that is meant to operate the relief valves. Due to this, I had to remove the lever that you use to manually dump the pressure in the hydro.

I wasn't so terribly wild about this as I don't like the idea of being stuck without the possibility of towing my 107. I may try to get the relief valves from a 782... the self-dumping style. This way I can still use the 129 pump without the complication of not being about to tow/move the tractor if it won't start. Generally I’m not wild about towing a hydro, but I’ve had to do it a few times in tight spots. If I can add the self-dumping style, that would ease my worries quite a bit. Would it still be safe to tow the tractor in emergencies with the self-dumping valves?

Thu Jan 26, 2006 8:30 pm


The way that the pressure is released (dumped) on the manual valves is... the flapper pushes down on the small pins that are in the center...on the top of the hydro valves. When under presure, the pins 'pop up'...the flapper pushes them back down, thus bleeding off the pressure.

The flapper shouldn't be hitting a 'bolt in front of the valves'. Are you certian the 107 has the correct 'flapper'?...and if so, is it installed correctly?

"Towing' a hydro is supposed to be a 'no-no'. Relieving the pressure (either by manually dumping, or self dumping) on the valves was intended to allow the tractor to be 'rolled' for a short distance.

BTW, the 'later' Quietline series tractors (pre 82 series) also used 'self dumping valves'.

Yes, either way (manual/automatic dumping valves) , as long as the pressure is 'released', the tractor can be moved without having the engine running.

Thu Jan 26, 2006 9:46 pm

The "bolt" in front of what you are calling presure relief valves is a plug for the implement relief valve (there is a coiled spring and a cone or cup under that "bolt"). On your 107, it is called a charge pump relief valve, but on the 129 that one is for the implement relief valve and there is a similar "bolt" on the right side of the front housing that is the charge pump relief valve. The two manual or self dumping valves on top are called check valves in the service and at least some parts manuals. The paddle on the release lever should not hit the "bolt" if it is right, unless the "bolt" is in a slightly different location on the ported pup. I have a ported pump out of a 149 right now, but don't have a non- ported one out, to compare the two side by side.

Fri Jan 27, 2006 2:53 am

The flapper on the 107 is the original one that the tractor came with i'm pretty sure. I wish i had a pic to post of it. Does anybody have a pic of hose that flapper should engage the valves? The flapper is hitting the "implement relief valve" just barely... but at least enough that i had to remove it in order to get the rear end back in the tractor.

Fri Jan 27, 2006 10:06 am

I'm going to try this again since I just lost it all trying to post pictures with it :x , and I'm going to post the pictures first


I checked the flapper on my 107, and although you can't see it to take pictures, you can "see" it with your fingers through the hole with the cover plate over it, at the front of the seat (that hole is for the gear shift on a 106/126), and it feels like the imp relief valve cap is at the same height as the check valves. If you look at the pictures of a 149 hydro (its standing upright on the rear cover in these pictures and is the same as a 129 hydro) and compare them to the 107 hydro you removed, I think you will probably find that the imp relief valve cap stands proud, or taller, on the 129 than it does on the 107, and that is why it was hitting the flapper/lever. I didn't know that, so I also learned something.

I guess a fix would be to swap out the check valves with self unloading ones, but at an added cost, even for used ones. You could also try to relocate the stock lever/flapper to make it work, but a simple fix would be to drill two small hokes in the tunnel, directly over the plungers in the two check valves, and then use a small rod or something to depress the check valve plungers when you wanted to roll the tractor - not as convenient, but just as effective.

Fri Jan 27, 2006 6:47 pm

Well, after yesterdays snowstorm i decided that i am going to return the 107 to it's previous state. I'm going to take all of the 129 parts off that i need and put them in the shed. I'll try it again when it gets warmer out. I had a 5 day window, and when i lsot 3 days due to a broken hydro linkage that kind of put me back more than i could recover. In addition to this, my hydraulic hose i was going to use wasn't availiable at the time i needed. So for now... i'm gonna use the manual lift and try it again in the summer. I did however learn a lot from this. I jsut need a tractor with a blower on it more than i need a hydraulic lift right now.