I have a 621 b ex military that’s a super low hr unit with original working meter that is at 249 hrs. And it shows it. It Has almost zero bowl wear and a fair bit of paint still in the bowl. I have went through and serviced everything but it has very slow labored steering. I haven’t been able to find much for trouble shooting this system. All steering cylinders were just repacked due to leaks from age. Anyone run into this? One other question, there is a two wire switch on upper right side of transmission at the hyd pump that has been damaged that I haven’t been able to locate and my local cat store is zero help.
Would you like to start with a Serial Number.? It will have a commercial equivalent somewhere.
Serial: 2DB00990 Sorry Nige, looked right over that important piece of info
Equivalent to a "commercial" machine of S/N 45P3594. Attached the Test & Adjust for the steering system.
Look at flats on switch good chance there is a number on it
What are the colours of the two wires coming into the 2-pin Sure Seal connector in the photo.? Orange & Purple by any chance.?
Sorry for delay. Only numbers I have found on switch is a 0449 and a 9x0008 that comes up to a flow switch. Nige the wires are both black from switch but harness side is white/black.
I would believe that's a flow switch. If you look close where should probably be a arrow for installation on it
9X0008 updates to 7T2074. It’s the steering flow switch. Methinks you need to replace it before going any further.
I agree. It is certainly directional based on the way it is drawn. I imagine that the function of the locknut up against the valve body will be to get the orientation correct.
I believe y’all are correct. It does have arrows indicating direction of flow and and I have confirmed orientation. Will replace and update.
Hi i dont have access to sis any more but with the flow light installed, it is fitted with supplementary steering . Supplementary steering pump is driven off the front of the diff housing. the ground driven supp pump and the main steering pump oil combine to give quick steering. If the supplementary pump has been removed or blanked off you will have slow steering. There are two steering pump options no supp steering option has a larger steering pump to compensate for no ground driven supp pump fitted. Can the OP confirm it still has the supp pump fitted? it was quite common in the day, to remove these pumps as they were quite expensive and troublesome. when we did, we just upgraded to the standard main steering pump
Yes it does have a the supplemental pump. I believe I’m starting to put a story together with this machine. Both the steering valve and supplemental pump are new. I have fixed damaged wires from steering pump and started troubleshooting finding linkage from steering box to valve stiff with short travel in steering valve spool. I think this machine has a linkage problem that someone just started throwing parts at without doing any diag on, once a solution wasn’t reached with valve and pump it was left to sit hence you low hours. I will update as soon as I work on linkage and test.
I seem to remember there being a spec for travel it might have been in disassembly and assembly
Is that it on Page 8 of the T&A procedure I uploaded earlier.? Attached the SysOp that might help in making sense of it.
i would also check the bearings and supports for the follow up and receiver cylinders. looseness here will limit valve travel Have you tried to bleed air from the servo cylinders? And one more, make sure the diff lock pedal is not stuck down. The pedal seize in the down position
So finally back to testing and have found short travel in steering valve. Specs show 1.120-1.150” I have about . 375 or 3/8 “ which would definitely explain slow steering. Looking for shims and procedures since my manuals appear to lost in the mail somewhere. After reading completely through T&A And sysop I’m not finding shims required as given for relief valves and such. Unless it’s a trial and error type ordeal?
I still think it’s in disassembly and assembly of steering box
You are correct. See Step 25 of the assembly of the steering gear.
Did you ever get a solution for this issue.?
Yes, sorry I should have updated but was pulled away from project for a bit. Valves were all checked for travel and free movement. Did have a short throw one direction at valve but if I disconnected linkage from steering box output shaft I could freely get full travel at valve meaning something is stiff between steering box and valve. After pulling shim assembly from steering box and checking for stiffness I noticed box would bind and then pop loose once enough pressure was held against steering wheel. Found bearing mount for steering box output shaft that goes through cab wall and is inside engine bay was seized. Replaced that and all is well. I much appreciate everyones help on this.