I've got a late 80s 953 track loader that I've been doing general land clearing work with. I've been noticing that after the machine gets up to operating temps, the hydrostatic drive slows way down. Loader hydraulics are still running good, just gets to the point that the trackloader is barely creeping around. Before it gets warmed up, it runs good, plenty of ground speed. I was hoping after I changed the hydraulic filter under the floor board that it would help but no luck. Next I'm going to try to drain the fluid and apparently there's a screen that needs to be cleaned. If that doesn't work, then I'm thinking maybe it's the hydraulic pump that runs the hydrostat? I'm new to these machines so any thoughts are appreciated! Serial number is 20Z00738
By the sounds of your comments you don't have a manual for it. That would help you with a lot of the maintenance basics including the correct oil for the hydrostatic system and where the various screens/filters, etc, are located. You can download one for $46 from Cat. Go to https://catpublications.com/ On the popup window click "Continue as Guest" Type SEBU5758 in the Search Box and hit Go. The illustration below should be top of the list. I'm sure that our resident track loader gurus will be around soon to offer more advice. Testing the drive system is something that has to be done methodically and in a certain sequence in order to correctly diagnose problems.
X10 what ^^^^^^^ said.
Thanks for the link, I need to get a manual for sure. Without going into unnecessary detail, the track loader isn't mine, I'm running it for a guy. And with hay season coming up, chances are I'm not going to have time to mess with it for awhile. So I'll probably be taking it to a local shop for servicing. But before I do that, I'm just looking to see if anyone else has experienced this and if I'm headed in the right direction in fixing it. Thanks!
Digging into the hydrostatic transmission is only for the really experienced, and I say that not in any attempt to put you off, simply to make you aware of how complex a system it is even for experienced mechanics. The chances are that the "local shop" won't have a clue and it ends up as a money pit AND still doesn't get fixed. An HEF member from Australia is one of the main gurus in Cat Track Loader Power Trains. Search for "Cmark" ........ Here's a thread on rebuilding a hydrostat. HeavyEquipmentForums
I don't remember saying anything about rebuilding the hydrostat, the hydrostat is fine, trackloader pulls itself even when barely idled up. The hydraulic pump that runs the transmission is on the side fyi, so even if I go that route I'm not tearing the whole thing apart. All the shop does that I'm referring to is work on 953s, 943s etc. Same shop that had rebuilt the undercarriage. All I'm having them do is change fluid and clean the screen to see if that fixes it. If not then maybe try that pump. I'm fairly certain that it's a hydraulic issue, not pulling enough fluid when idled all the way up, something like that.
I like your confidence. There's nothing this site needs more than confidence. On the other hand, expert advice just might be worth something too. Or the manual, nothing wrong with reading the manual.
Problems in this area have been gone over pretty extensively before. A little light reading to start you off.... HeavyEquipmentForums HeavyEquipmentForums HeavyEquipmentForums HeavyEquipmentForums
Having never touched a hydo trackloader I can't add much except I think in any hydraulic system one needs to understand that there are at least three basic components. A pump that creates flow and pressure. A valve system of some kind that directs that pressure and flow to where it can do some work. Last a motor or cylinder that actually does the work. Does that sound right Cmark? So until you know what part of the system is not doing it's job replacing any one component is a big gamble. Not to mention the problem of cleaning the complete system if there was damage to one part of the system.
Yes, that's it in a nutshell. The basic hydrostatic drive loops are fairly straightforward. It's only when we look at the other systems that keep the tractor going straight when you want it to, turn when you want it to and keep the engine running at the optimal RPM under all load conditions that things start to get interesting. Especially when you consider that it's all is done with hydraulics and mechanical linkages, and zero electrical components.
T Thank you for your response. Thank you guys for your response. Now we are getting somewhere. Does it seem unusual that this machine runs perfectly fine, until it gets warmed up then it starts getting slower and slower? Still maintains power through the lift cylinders just ground speed is slower. I should also mention, when you pull the throttle all the way back to full throttle/operation notch or whatever it runs slower there too. Until now the guy who owns the loader just had me run it a little idled down and it ran fine but I've noticed it's getting slower after warming up.
No, it's not unusual at all for a hydrostatic machine to slow down as it warms up, that's usually what happens when the hydrostats are failing. Which might be why Nige mentioned rebuilding them?
I finally got some time and read through the thread of Auzziegold's 943 and the issue he described is exactly what this machine is doing. He even tried changing the trans filter like I did to with no luck. So I'm definitely going to do some more looking into the underspeed valve and underspeed override valve. Regardless, I'm going to go ahead and change the hydraulic fluid just so it's done, no telling when that was done last. Thank you cmark for posting that thread and pointing me in the right direction!
You're welcome. Please don't overlook checking the engine RPM at high idle. It's important.
Sorry if I somewhat confused you. I was alluding to Cmark's bona-fides as a guru on that product line, I was not stating that the hydrostat required rebuilding on the loader you're running.
Will do. I'll keep you updated.
No problem man. I just didn't want to get down in the weeds about a full rebuild on the hydrostat because I really don't think thats the issue here and especially now that I read through that other thread. I apologise if I came across a little rude, just trying to keep the thread corralled. Ive got access to a manual, ill look through there and do a little more research but I think we are heading in the right direction!
All good. If you need any assistance with technical information please shout out.
I had a few do this and the metal lines going to the servos were leaking replaced the fittings and worked fine
Thanks! I'm hoping to take a look at it this week. I'll keep you posted.
Good news! I got the trackloader back and was able to put it to work this week and it ran like a top. Ground speed was excellent, was able to run it all the way back into the detent. The shop that I took it to did the following. Adjusted the left pedal Disconnected the seized brake pedal Rebuilt a seat valve on the transmission Changed fluid This is the best this machine has ran since I've been on it! Thank you guys for your input!