Hello, this is my first time posting here, glad to connect with fellow cat owners. 

I have a cat 910 loader, approximately a 1978 model. Serial number 80u3058. It has 3 forward gears and 1 reverse. It has always took quite a bit of throttle to get it to move but recently got to where if trying to back up an incline or out of a hole it wouldn’t move, even at full throttle. It’s sluggish to move in forward as well. 

so I took the top cover off the transmission and hooked a gauge up to the middle port that is supposed to read trans drive pump pressure. Mine has 25-30psi where the book shows it needs 280 or so at idle. I replaced the trans drive pump today and it made no change. I decided to take the top cover back off and look for leaks with it running. I have a pencil sized steam of oil shooting out the hole with the red arrow on it in the included picture. Is that normal, or is that where part of my problem is coming from? Any other thoughts for things for me to look at and try to remedy this problem? Thank you for any and all suggestions! Ryan Payne

Sounds like the modulating relief valve spring is broken.

Thank you for the reply, I will check that out tomorrow

Well i took the control valve completely apart that the pump is bolted to. Everything looked fine as far as I could tell. All the springs were intact and none of the spools were stuck or anything. Also I took the neutralizer valve apart and everything looked good in it. I have pressure to the neutralizer valve and when I push the left pedal down have oil returning from it to the trans housing.

For information I tested the primary clutch pressure on the pump. The book says it should have 60 psi at full throttle and it does. At idle it has 25-30. This is the same exact pressure reading I get at the port to check pump pressure. Does that mean anything, or does anyone have any other ideas of things to check? Thanks in advance!

Don't know how much this has to do with it but the instructions say to remove plug "C", the one in the yellow section on your valve while checking primary pressure.
There are also two additional valves to check, the neutralizer signal valve and the neutralizer safety valve. Did you check both? Not a good idea to be running unit with such low pressures as your surely starving lubrication system pressure.

Thank you for the reply. I did have the plug (c) removed when checking primary clutch pressure.

The only neutralizer valve I have found so far is the one at the bottom of the left hand neutralizer/brake pedal. I’m not sure which one of those valves that is but it has a pressure line coming from the pump in the transmission and a return line to the trans case. I saw the other neutralizer valve in the diagram but have not been able to locate it yet.

I’m only running it long enough to try and troubleshoot now. It will move in forward gears but hesitated to move in reverse and won’t move at all in reverse if In a bind at all like trying to turn or back up a small incline.

Have you checked the oil pump suction screen?

 
 

Screen was very clean except for these few pieces of what appear to be friction disk material. 3rd gear has not worked in this machine since I’ve owned it so was hoping they were related to that but might or might not be.

 

Hi Team,
too long ago to recall clearly but as OM said the plug in the yellow cap of the main trans valve pack is removed for checking Initial/primary clutch pressure--with this plug removed a small amount of oil thru an orifice should flow, this low pressure helps to start clutch engagement at a low pressure--when the trans is engaged there should be oil supplied to the area below the plug to start a modulation of the clutch pressure up to full clutch working pressure.
Oil to the area spoken of is pushing a load piston to increase the spring pressure of the modulating clutch pressure relief valve.
This oil is supplied thru an orifice and if the orifice is blocked clutch pressure will not increase as designed--not sure if these had a white nylon orifice with screens built in--if the screens are clogged or the orifice is clogged the low pressure you have would be the result.
Cannot recall if said orifice can only be installed one way or else flow thru it to the load piston could be blocked--it may have a larger flange one end to prevent incorrect fitting
I stand to be corrected.

No books here for this late a unit so I am going from memory.
Any chance you could post a picture from the Service Manual of the Trans test ports showing the test port application on the trans pump/valve pack please. You may or may not be reading T/Converter charge pressure--I cannot recall where it is measured and may be off track here.
Cheers,
Eddie B.

 

Thank you for the reply Eddie. I am away from my book tonight but will post a couple pics I have on my phone. And get more tomorrow.

Thank you very much for the explanation of how the control valve works and starts to fill and engage the clutches. I’m not much of a mechanic. I have the oil flow diagram but still didn’t completely understand how everything worked. I couldn’t figure out how pressure ever moved the load spool. 

That orfice you speak of sure sounds like it could be the culprit. I wonder if it is number 11 in this oil flow diagram. I removed what the book calls the “slug” number 12 but at the time didn’t realize there was an orfice above it so didn’t check it.

I will get better pics from the manual tomorrow. Thank you all for the help!