1978 Cat 931 Serial 0025Y00761 Just getting ready to start on this. Would like help on diagnosing the problem. Bought this knowing it had this problem. Everything on the machine seems to work fine, low hrs. but I have no turn to the right. Doesn't even seem to try. I do have the original service manual. Fair experience on tractors and diesel trucks but never had a track machine before. Done a fair amount of reading and have some ideas but I would like to at least try to start in the right direction. Any help is appreciated. Thanks! 051
First of all, we need photos!! Second, there is a very recent thread on a 955 having the same problem that you probably should have a look at: CAT 955K No power or brake to right track It surprised me--the problem turned out to be pretty well right at the track sprocket, when I think a lot of us figured it would be a broken shaft or stripped gears downstream of the clutch/brake assembly. So...if the right track drives but won't clutch, does the brake work on that side? There's a start. Guys 'way more experienced than I will probably chime in very soon! Jon.
I have power to both tracks. I dragged a big tree across about 200 yards of pasture the other day and it pulled straight as an arrow. I've also done some digging on a pond dam and pushed a few trees. Both tracks pull fine. Just no turn to the right. I suspect the clutch but would like to be more sure before I tear into it. 51
About the only other hope for an easy fix is to pull the floorboards and see if the linkage between the clutch control and the clutch housing is working; in other words, when you actuate the clutch, is the control shaft into the clutch housing working? I'm thinking old school here- assuming mechanical linkages, but if it is hydraulic assist you may have to be a little more crafty in how to establish that the clutch is being actuated when you are asking it to. Jon.
Try adjusting the brakes as its the first place to start, on the small kit like that you will find a hex rod on each side sticking up, tighten this just firm, then go underneath the back case and adjust the support bolts just firm, then undo the support bolts 1 full turn and lock off with the nut, then go back to your brake adjusters and undo them 9 flats (1 1/2 turns) and check the peddle height, if all feels good give it a try. tctractors
955 is wet brakes and a different animal than a 931. On a 931B there is a roller on the steering valve that can get a flat spot and not fully engage the steering clutch. If you push the pedal half way down do you lose drive on the right side? That might help to determine if the steering clutch is working properly or contributing to the no right brake problem. If you adjust the brakes like tc said above, with the brake band adjusted tight shorten the linkage as tight as it can go by hand (and the linkage pin fits in easily) and then loosen off the linkage to get the correct pedal travel. This insures that the free play is at the brake band and not in the linkage. Learned this from Bob/Ont. There are some differences between the 931 and 931B but I think the brakes are similar.
Does anyone know what the PSI should be coming into and going out of the Steer clutch control valves? See drawing. The red and the blue. Thanks! 051
On the half way down question. No it does not loose drive on that side. I tried this when I was dragging a heavy tree just to make sure. The left side 1/2 way would cause it to start going left (before brake engagement) but the right side made no change. I can feel the right side brake trying to work if I really force it but it seems like I'm just overpowering the clutch. 51
RH steering clutch not disengaging maybe.?
It does sound like the right steering clutch isn't releasing. Don't know the pressure on a 931. I think it's around 325 PSI on a 931B but not positive. I think having your steering valve checked out especially in regard to the roller #19 and the cam that rides on it (#11) might be a good 1st. step.
OK, That's where I'm going to start. Should be able to start turning bolts tomorrow. Will advise what I find. Thanks! 51
The common fault that I have found with the steering control valves is springs broken, the other common fault is rusted up steering clutch packs, this involves removing the steer clutch and stripping them down, a lot of rust removing and re-plating. tctractors p.s. there is a pressure test port on the slave cylinders to check the steer clutch is being activated, they are on the outside of the case.
Pic attached, is this the port?
When I depress the clutch I'm getting really good strong flow out of this line, knocks my finger right off. Have not tested the PSI yet but now that I know there is a test port I will do that to confirm.
Cam and roller looks good. The control valve has good travel the movement feels good as far as I can tell.
Well, I don't know how I got double pics and don't know how to get them off. ? Anyway, at the beginning of post someone ask for pics. Here's a few, the best one is the hr. meter.
NEVER EVER use your bare hands to check for leaks or hyd. flow. If the fluid is under pressure or has a pressure spike it can penetrate the skin and potentially kill you. Some have lost fingers and messed up there hand functions. I wouldn't trust the hour meter at all. The track frame guards are missing and it looks like the sprocket counterweight is welded on. Check how the rollers turn and look for flat spots on them. I think the plug on the side is the test port. If that all checks out, it's looking like the steering clutches are the problem. You have a very early 931B not a 931. This is very important to list when asking for advice. Full serial number is most important though and your machine is a very early 1980, the 2nd year for a 931B. The steering is different between the 2, similar but enough difference you have to look at the proper parts and service manuals. I should have noticed the 25Y serial number as a 931B. I have a later "Improved 931B" 25Y serial number that has some improvements over the early ones. Higher lift height for one. There were also some slight changes after my serial number. The steering clutch valves were changed is one of them. I got a brochure on the Improved 931B from the Cat dealer here and learned of the different steering valves from reading posts on here and looking at parts manuals.
I did notice that my control valves are not the same as the diagram I posted on the 28th. Mine don't do the crossover control of fluid. I did find the spec for the pressure in the book, it is min 270 PSI to open the clutch. 51
that's a sweet looking machine!
These little shovels are very simple and very easy to work on, the test port in the rebated hole is where you need to hook in a pressure gauge (0 to 600 psi) test both sides as it might help you fathom things, but as I have already said the steering packs can be rust locked, best of luck. tctractors
265 at idle. Going to start tearing into the clutch are now. 51
Well, of all the things I expected I might see, this was not on the list? Looks to me like my clutch should be disengaged all the time. The hyd supply to the cylinder is not even connected but???? Any thoughts?
Your pic. isn't very clear but is the line going to the cylinder missing about an inch just behind the fitting? If so you would think there'd be a bunch of oil in the bottom of the clutch housing from pushing on the pedal. I wonder if the piston is stuck? It was several years ago when I did my steering clutches and I can't remember too much about the internals. You may not have to pull your steering clutch out if the cylinder and the line to it are the problem. If you remove the cylinder, be very careful loosening the bolts. Mine were extremely tight and I was worried about them breaking. There's a spring in there (you can just see the top of it in your pic.) that I remember is easy to remove/install and there's enough room to do it with the cylinder out or the rod that goes into the cylinder out. Trying to put it back on with the rod in the cylinder is a pain. Sorry I can't remember better. I just remember it can be done without everything being back together. I did put new bushings/ball sockets(?) for the ball ends of the clutch arms. Heating them did nothing but melt some plastic plugs Cat put in threaded holes for attachments. I ended up using a large very clean cutting tip in a torch and cut them almost all the way through lengthwise. I didn't want to damage the bore they fit in. Then I used a chisel in the notch I created and was able to turn them and get them out. It says to grease the ball sockets but the shop that did the clutches said to use dry graphite instead because grease just attracts dirt and brake dust, etc. The new ball sockets were a beatch to pound in. I'm sure cooling them would have made installation a lot easier. I'm not really sure I needed to replace them though. If you pull your clutches you could check them. I figured they were rather cheap to replace considering the cost to do the clutches, $3500cad. a side!
I think I'm not wording it clearly. The line not connected is one I took off the controller valve. What I'm saying is the cylinder is extended and I know it has no hyd pressure on it. I was able to compress the cylinder easily, but the yoke won't move. It seems like the clutch would be disengaged not engaged. 51
You can see by the adjuster bolt on the left the yoke is almost all the way to the left? At least that is what I think so far? 51
Well maybe I'm missing the whole problem. There is still about 1/4" left before the adjustment bolt hits the case. So if the yoke traveled another 1/4" would that release the clutch? 51
The bolt is just to limit max. travel if I remember right. I think there's a measurement in the Cat specs. You don't want the piston over extended. Also if I recall the yoke should move some. If the yoke is solid, I'd tend to think the steering clutches could be rusted/seized up. Maybe see if you could pry it back some. If you can get some movement, you might be able to free it up.
Sometimes you just get lucky. My clutch is working now. I did a lot of wiggling on the yoke and adjusted the rod between the cylinder and the yoke out probably 1/2". Rigged everything up temporarily to test it, bucket for a seat and all, and she works!! Going to put her back together today. While I obviously don't know what I'm doing, I do think the root of the problem was the adjustment of the rod between the cylinder and the yoke. I think someone had it too short. As a result the pressure plate was never depressed, the clutch never released, the yoke just stayed in one place, that's why it was stuck at first. I do really appreciate all the hand holding on this. 51
Check to see what the measurements for the stop bolt and the length of the rod in the cylinder are supposed to be. Glad it seems to be working now.