973 slow

[farmer bob]

Would anyone know what might cause it to move slow? No power loss, just doesn't drive forward or back fast.

 

[DMiller]

s/n? Year ? Series?

 

[farmer bob]

86g000173, 1984 I believe. 1st series.

 

[Cmark]

A couple of standard questions to get the ball rolling.

1. When travelling, if you slowly move the throttle lever back towards idle, does the ground speed increase?
2. Do you know what grade of oil is in the transmission? Has it been changed recently, and the filter?

 

[farmer bob]

Filter and oil gas been changed within the last 200hours. When moving the throttle towards idle, the machine slows down. I read in my service manual that there's a rod that connects the transmission linkage to the throttle, so that it will only go into high speed at WOT. Not sure if I'm right about that though.

 

[Cmark]

The underspeed override valve is to disable the underspeed function at less than WOT. It in itself won't cause your problem but by closing it and therefore disabling the underspeed function you can do a crude check on whether the underspeed valve is working, hence the question about gaining speed when the throttle is moved towards idle. You can also try disconnecting the linkage to the underspeed override valve and letting it drop to the bottom of its travel.

Is this a new problem or has it been getting gradually worse over time?

 

[farmerlund]

Did you cut open the last filter? I would change it again and inspect the old one for metal. At lest you will know if its on self destruct or not.

 

[farmer bob]

I notice that when the machine is cold, the speed is quicker than when after running for an hour. I'm not sure if it's a real thing, or that I'm expecting a 30ton machine to handle like a skidsteer.

 

[rmllarue91]

Hey farmer Bob I remember having that issue on a 973 let me think about it but that's definitely and issue they have it's been awhile since I worked on one might have to grab a book

 

[farmer bob]

Like I said, I had changed the filter, which looked good but I did it for a preventative maintenance schedule. I had a drive hose blow and when I replaced the oil, I didn't use cat brand oil. Not sure if this is the reason for the slow moving or not.

 

[farmerlund]

A good running 973C will rip around like a giant skidsteer.

 

[farmer bob]

I've tried to find out information on what the charge pump does. The one that only uses about a gallon of oil.

 

[farmer bob]

Does anyone know the function of the charge pump and if it's associated with the forward and reverse movement.

 

[Dickjr.]

https://www.google.com/url?sa=t&rct...ans_tips.pdf&usg=AOvVaw1zTsk1yt-4gpA23ixi1ClD


This might help if the link works

 

[farmer bob]

Would it help to replace the hyd oil with higher visc? I got the cat from a dealer in Kentucky. I don't know what they used for oil, but maybe they had higher temp oil in it. Like I was saying, it reacts and drives and pushes faster when its cooler. But after the trans gets to operating temp, it gets slower, but still has the pushing power. It started all this after I ruptured a drive hose and had to refill the reservoir. I don't have access to the testing equipment required. Is there adjustments I can make, like the main pressure relief valve or the underspeed cut in valve to see if it helps, or makes it worse.

 

[farmer bob]

Also the drive pump requires 1 gallon of oil. I haven't been able to find any info as to why it needs it's own oil. Sorry for my ignorance. I've got the service manual and it only says it needs 1 gal of oil

 

[Cmark]

What oil did you put in after the hose failure? Correct viscosity is vital to the operation of these things. It should be an iso32 hydraulic oil or equivalent, the best quality you can get. There's too many high pressure hydraulic shenanigans going on in there to risk putting cheap oil in.

I would recommend starting with an oil and filter change using a Cat filter and Cat HYDO Advanced 10.
Also.
It's the pump drive which takes a gallon of oil. It's basically a splitter box which drives the two travel pumps.

For more info on how it all works, take a look at the 953 tranny overhaul thread.
https://www.heavyequipmentforums.co...atic-transmission-overhaul.41449/#post-472532

 

[farmer bob]

Would it hurt it to put iso46 or even iso68 oil in the cat? It's not going to be uses in the winter. So the low temps won't come into play as far as high viscosity.

 

[mikebramel]

68 is too thick

 

[farmer bob]

Holy ****!!! That's all I can say. What a difference using the right oil can do. It handles just like my skidsteer. I put iso 46 oil in since the machine has 11k hours. I hate to admit that I had had put in 303 universal hydraulic oil in before.