So I have had the valve body out four times finally got my clutch pressure up to about 260 after fooling with the piston and some little plastic filter. That is not in any parts book. I finally got the pressure up. Ran it for 45 minutes and lost pressure again, it seems that the spool valve in there is not sliding over far enough to block off the relief hole not sure That I did anything specific other than clean out that orifice. I think if the valve would’ve moved far enough, I would’ve had the required 300 psi everything else seems to work correctly the fire shifting so I know that transmission and the torque converter is OK I’m assuming that that valve body only runs the clutch packs but I’m not 100% on that, I have replaced the screen and change the oil twice because I put 30 weight in it the first time and then found out that I was supposed to have 10 weight in it, but that didn’t make any difference there wasn’t that much debris in the pan the screen I took out was basically plugged so I thought that was the problem but it’s that didn’t have any bearing on the operation of the clutch packs
I am referring to the steering clutches.
I guess I forgot to tell you guys it’s a 79 caterpillar D3♂️
Also, I’m having the same issue on both sides so I know it’s not the steering clutch valves. I’m about 99% sure the problem is in the valve body with one of the piston or spool not moving far enough. I forget what it’s called in the Parts book.
Forgive me for the picture posting, I’m learning with the system here that last picture of the valve body you can see that little red piece sticking out of the end. That is the little filter. I’m referring to that does not appear in my parts manual. I don’t know if that was something that Cat added after the manual was printed I’m assuming but I’m not really sure what it’s there for. It’s a little screen it almost looks like a little tiny filter you’d see in a carburetor.
To look up technical/parts information a Serial Number would be a whole lot better.
I'm not sure if the D3 has rollers on the shafts of the steering clutch valves. On D3B's they are a very common problem. After a few thousand hours they get flat spots on them which causes the valves to not fully engage. Would need to look at a parts diagram or steering schematic to see how the valves and linkage work.
Hey! Get those gloves off! You have to get your hands dirty here
79U3439
I’m convinced now that the pressure loss is once the dozer warms up. I’m thinking the guy sold it to me knowing this. It will work fine when cold so I’m going to get the radiator cleaned up and check the thermostat. Should I switch from 10 to 30 weight in the trans? My dozer is right after they went to 10w I guess I’m taking the valve body out again. The piston in the valve body that moves to build pressure for the clutch valves is somehow related to the orifice with the tiny filter that’s not in my parts book
No just a plunger but all that is ok
You need the full service manual for your tractor, the full service manual give you the schematic diagram and explanation of exactly how the clutch hydraulics system works. From there, you can figure out where to go look for problems. Pressure loss once a tractor warms up indicates either a worn hydraulic pump or loss of pressure from the likes of a damaged o-ring somewhere in the lube system. The system should work just fine with either 10 wt or 30 wt oil. It's just that 30 wt will provide a more sluggish response in cold weather. So Cat probably went to a recommendation for 10 wt to improve hydraulic response when it's cold. If the parts book you have covers your tractor serial number (this is listed on the front cover), then the filter will be listed in the parts drawings. Sometimes parts are difficult to find in Cat technical parts drawings, they're not the easiest drawings to follow, other manufacturers provide better drawings with exploded views.
You might be able to find 10W-30 in a TO-4 oil. The shop that did my engine said a 10W-30 works good in the trans. I think they used a Petro Canada oil. The engine and trans. have to come out together.
I have a 931 I'm scraping if you need a part for the transmission I believe there the same
How much would you sell the valve, body and pump for? I am in Tennessee.
I have both the cat manual and a knock off version. I took the pump all apart and everything looked perfect. The piston in the valve is what I think is causing the problem.
I have a question that has bothered me since I started working on this machine. Why did they not plumb those clutches in with the hydraulic system? The only thing that I can think is that the pressures would be too high for the current piston, but that would not be a big deal if you were manufacturing a machine, install a separate pump inside the transmission just to run two little dinky cylinders when you could’ve done that with the hydraulics Asking for a friend lol
Something to add to this equation, when I first got the Dozer the first time I ran it was about an hour and this was before I knew anything about how steering clutches worked. The brakes seemed like they were acting up and I couldn’t turn, so I just assumed that the brakes needed to be adjusted. Not realizing that the reason it wouldn’t turn probably was because the steering clutches weren’t releasing, everything worked good enough though for me to actually park it in front of the shop and I was able to steer well enough to get it put off to the side of the door fast forward two weeks and I went to put it in the shop, and I could not get it to turn at all. So the whole time I’ve was working on it in my mind something went wrong when it was sitting there or I was just lucky to get it parked. Once I took the valve body apart and ran the dozer with the cover of the transmission off I realized that it was dumping fluid out of the bleed hole for lack of a better term because the piston wasn’t moving over and blocking that hole, allowing it to build pressure so after taking it out four times and taking some shims out of, the main spool that appeared to have something to do with that and cleaning that filter all of a sudden it worked so I thought I fixed it even though I wasn’t 100% sure what I did actually did anything, taking the two shims out seem to me like that would allow the piston to go further I got 260 psi, the system calls for 300 so I just assumed that the piston would move over far enough it would get 300 because it was still bleeding out that hole a little bit. I don’t think I have a issue, but then again , running the dozer in the shop necessarily get it up to temperature the first time I started it with the transmission cover off though oil all the way to the ceiling so I knew I had a significant amount of pressure being lost that weep hole. OK for the confusing part. in my mind when I parked it, I had a break adjustment issue. When I went to move it, I could not get it to turn at all. Literally I could not stand on the brake, Paul hard enough I drained the transmission and there was some debris in there, but not a lot the screen was plugged. It was the newer screen, I installed the old style screen new 30w no improvement it wasn’t until I took the valve apart that I actually got it to build 260 psi. Upon previously testing we could get maybe 15 psi The confusing part is when I bought the machine and ran it cold. The clutches worked. After I ran it at my shop and the clutches quit working. I parked it when I started it up cold, and it was colder, they didn’t work at all. After doing all the work with the brakes, I ran it for about 45 minutes and the clutches quit working again so I parked it and I started it up again the other day and the clutches were working just fine. About 45 minutes once the machine got warm. The brakes were basically wore out from being run with non operational steering clutches. Like Oz said, there could be an issue with the pump once it gets warm it just may not have the power
Let's verify it's the same 250 will buy if you want the whole transmission for that it's your I'm in pennsylvania
How is the engine?
Runs good send me a dm