Diagram with labels....
If your getting flow out of that port your getting flow through the orifice.
 

Hi Team,
if indeed the orifice (11) is in place) it seems operative as OM suggests BUT your description of a pencil sized flow from the load piston port, that limits the load piston travel to increase clutch pressure seems too much and may be stealing a lot of your system oil flow.

Is the pencil sized flow column (Diameter of the dump port) large or small---high or low ??

Oil flow at the said port I believe should be a meager flow rate, there is a slug (12) that slides back and dumps load piston activation oil quickly to effect a quick clutch pressure decrease so as to set the load piston back to its lower initial pressure value/setting ready for the next shift and this oil should dump out a drilling in the end face of the yellow end cover.

Again this description is from memory and reference to the diagrams supplied. There should be a truer description in the Transmission and Valves Operation section of your manual.

From memory, I seem to recall the nylon that the orifice body is made from on these being cooked hard and crumbling to pieces so it may be missing--I stand to be corrected.

Cheers,
Eddie B.

 

 

 

 

Thank you for the reply.

The flow I’m getting from that load piston port is pencil sized and if I have the top transmission cover off it will shoot at least a foot in the air. That makes it where I have to set the cover back on to test so I can’t watch what’s going on in there like id like to. It seems like a lot of oil and pressure to be coming from there.

When I had the control valve apart I removed the slug (12) looked it over and put it back in. I will admit I did not see any type of orifice body in the passage that slug was in. I will pull it back apart to check that and see if that orifice is still there or it could have possibly came apart. I also need to look that end cover over more closely to make sure it’s drain hole is open. I need to pull things back apart and look at them closer. I’ll include a few pics from my manual of the test ports and a parts breakdown of the control valve. Thanks!

Hi,
I would suggest you check if the plug (17) 3D4603 in your attached parts diagram is in place--it is listed in a chart I have but it does not give an orifice size so may only be a 1/16" NPTF plug which does not make sense as an orifice is needed to control the rate of modulated pressure increase--perhaps the orifice is drilled into the valve housing and this plug blocks the drill access hole after the orifice was drilled.

Next I would try fitting the test gauge to Port D, P1 (clutch pressure) on the valve body and see what you read--it should be the same as the pump test port in this instance.
When the machine is put into gear the pressure should rise to the Clutch specification at both ports--if not slightly higher at the Pump test port due to restrictions to oil flow thru the valves etc.
Cheers,
Eddie B.

Primary clutch pressure (port D) should be 60 psi with selection in neutral and (plug C) removed.
Pressure is controlled by modulating relief valve (6).
Operating clutch pressure should be 280 -300 psi approx with selection lever in third speed, right pedal activated and converter at stall.
It would seem that if you have no third speed and low clutch pressure there is major leakage at the third speed transmission clutch and possibly others.
If you wish to see what is going on at the control valve during various speed changes make a temporary cover out of plexiglass.

 

 


I took the control valve back apart today, the plug 17 was in place. There was no orifice in it and behind it is just a hole the diameter of the plug into the passage where the slug is. Beside that is another open hole into the same passage I assume is the drain/dump hole. I will include pics. I did not find an orifice anywhere near that passage however that slug does have grooves around its circumference.

I did however find an orifice on the other end of the control valve that I had not seen before. And it was plugged with a tiny piece of rust. This is on same end of the valve as the modulating relief valve. I cleaned the orifice out and blew through it with compressed air. I couldn’t see any way to remove it to clean it out any more. I am going to change what the parts book calls a check valve on this end of the control valve as well since I removed it to clean everything up. I will include a pics of all this.

I will test clutch pressure when I get everything back together. I hadn’t considered making a top of plexiglass but very well may do that. And you are right I sure may have major leakage at the 3rd gear clutch and others. It may just be time for a rebuild, just wanted to try everything I could before I got to that. I really appreciate everyone’s help and replies!- Ryan

I'm a little suspect of the yellow block section of your control valve. Doesn't match rest of the valve. I wonder if some cobbler has been in there before?????
Do you have the Service Manual for the 910? Should shed more light on what may or may not be missing.
Edit: Looking at the flow diagram there a five places shown as restricted or orifice flow. All need to be checked. Your finding a blocked orifice on the modulating pressure side of the valve may be significant.

Hi,
the green arrowed port is a drain passage for the load piston when the slug moves back after a gear shift etc. The port to the left of the slug should be where load piston orifice flow controlled activation oil comes in to modulate the trans pressure rise, at this same time the slug moves inwards to close said dump port--from memory.
Next thing is to refit the valve with the cleared orifice and retest--one step at a time so you know what made a difference.
Then report the difference so we can move on.
Cheers,
Eddie B.

 

Well I got the loader all back together today, fired it up and tested it out and it moved back and forth good! Put my gauge on the pump pressure port where I used to have 25-30 psi and after a couple seconds it pegged 280 psi just like it’s supposed to! Just for another test I backed it on to my drop deck trailer and it backed up the ramps no problem. Last time I used it it wouldn’t back up a little 4 inch rise. I think she’s ready to go back to work.

I am very greatful and thankful for everyone’s help, especially Old Magnet and Eddie B. I appreciate y’all taking the time to explain how that valve works and possible causes. I would’ve overlooked that plugged orifice if it wasn’t for that. Hopefully I can help someone out someday, thanks again! Ryan

Congratulations!!!! Your patience and thorough investigation paid off!! Sure beats a transmission overhaul.