On one of my 973's the guy I got it from adjusted some stuff on the hydrostat linkages. I'm wishing he hadn't. Running it on a big pond the last few days if you back the throttle off just a little it runs faster. I changed the hydro filter thinking that was the problem, it helped but didn't cure the problem. Messing with it today I notice when I back off the throttle just a little the spring loaded linkage still has the motor running wide open but another linkage off the throttle backs off an arm that goes into the hydrostat. Does anyone know what this arm does? It also tracks straight most of the time but sometimes the right side doesn't pull as hard. Sometimes it gets real sluggish at wide open throttle but not all the time.
Hopefully Cmark will see this. If not you could send him a PM.
You have some different issues going on here. A problem with straight tracking is unlikely to be related to a ground speed issue. The linkage you speak of on the hydrostatic case is connected internally to the underspeed override valve. The underspeed override valve lets the transmission operate when the governor lever is not set at high idle. If, as in your case, the machine gains ground speed when the underspeed override valve closes, that suggests an internal leak in the control system. To correctly set the underspeed override valve: 1. Engine off. Disconnect the underspeed override valve linkage. 2. Set the governor lever to high idle. 3. Lift the underspeed override valve lever until you feel a light resistance from an internal spring. 4. Adjust the linkage until it connects easily to the lever. Also see: Cat hydrostatic transmission overhaul. Over the next few days, I've got the job of overhauling a Cat 953B HPCU. The 943, 953, 963 and 973 B series and earlier are all much the same. Anyway, due to the fact that these machines are getting scarce in front line work nowadays, and the relatively high cost of repair I think this may be... HeavyEquipmentForums Caterpillar 973 failure greetings to all forum members. first of all apologize in advance because my language is not English, but have started to work google translator to understand and communicate with you. I recently purchased a 973 serial cat 66g, at first glance the machine does not wear this because I never... HeavyEquipmentForums
Outstanding! I never realized Bob/Ont was so well versed in the Cat hydrostatic loaders. Makes sense though as he was the guru on the powershift models.
I worked on that yesterday, everything was out of wack. I'm guessing when you mean high idle that would be wide open throttle? I unhooked the lever and you can pick it about half way up and it seems to be free till you hit one spot and then has pressure on up. I set it at that spot with the throttle wide open in the notch on the throttle lever in the cab. For some reason he had it set where you couldn't pull it to the notch hardly and it would kill it at about half throttle. Now it pulls the spring on the throttle about a 1/4 after the injection pump is wide open. I ran it a while today and it seems to work better. This machine seems down on HP compared to the other one I have but the other one has had the pump rebuilt and it has well worn pads and this one has almost new double grouser pads. Headed to a big lake end of this week so I'll know more in a few days.
Did some more adjusting a little is a lot on the hydrostat lever. It's real close to my other machine now. One other problem I'm having is the drive oil heating up. When it's 90 or so outside and I'm pushing it hard it will heat up to around 220.This is with the factory gauge I need to use a hand held temp gauge to make sure it's right.A friend told me on the older machines they have enough wear it's hard to keep them cool in hot weather. Has anyone changed to a bigger cooler on one of these machines?