I am working on a early SERIAL number loader with the electrical plug on the bottom of control valve so to opperate the shift Solenoids. The transmission has no 1st gear it has a strong 2nd and 3rd and a 4th that will not pull off at a stand still I don't think it was intended to do that anyway. My issue is back to 1st gear reading the manual my understanding is all three range Solenoids must be powered off to allow 1st gear clutch pack to apply. Right? My experience in hydraulic Solenoids just because it's on or off does not nessary ensure fluid has been moved to desired port. " valve stuck" condition. Can anyone tell me where the problem may be I have pin tested CN 16 harness plug and the ground signals are correct on the switch side of harness. Troube shooting test showed 24v on the 2ND 3RD AND 4TH RANGE Soleniod related pins on CN16 transmission SIDE OF harness. "Is that normal until a ground is applied" Customer only needs 1st and 2nd gear what conditions need to be met so to have these two ranges Farward and Reverse work fine. Thanks for your help ...
Assuming you have no first gear in both forward and reverse, before you go digging into the electrical system, have you considered pulling the suction screen on the transmission (or the filter & cut it open) and looking for burnt clutch material..? You could have a failed 1st speed clutch.
You might provide a serial number as well so we know what you have. Komatsu merged the Dresser line into their product line and used different transmissions between the Japan and US built machines. Also, yes the usual way the wiring worked was by grounding the circuit to allow current flow to energize the solenoid. There were also harness problems on some of the units over the years and we found out it was possible for cross talk in the wiring harnesses. Normally only two solenoids are engaged at a time to operate. A direction pack and a speed pack.
Yes the fluid and filter was clean.no signs of clutch pack failure.
The serial number is low it's one of the first machines built the harness plug inters the valve body at the bottom of control valve. It has Solenoids for Farward one for Reverse it has 3 more for clutch pack 2,3,4 when all of these are off, that's when I st gear clutch pack is pressurized with pilot pressure and a spring on the spool keeps it in first. I am 50 miles away from loader so serial number is not available until I get back over there next week. Anyone correct me if i have stated how control valve works incorrectly have never seen one of these loaders until I paid for a manual last week....and pulled up on the job. There is a manual fwd , reverse valve for emergency use. . If I unplug harness and move spool to Farward or reverse as in a electrical failure will that place loader in 1st and eliminate the cross feed issue.
I've not seen a transmission on a Komatsu work that way for first gear but what I had worked on were WA380 and larger. If you use the emergency shift function and it goes into first gear either direction should indicate an electrical problem. The issue could be in the harness on on the shift control box on the steering column. Be very careful you don't get run over. On the bigger machines you had to hang off the side of the machine to push the spool in and the machine moving was a real likely possibility.
Thanks John right now it shifts with the emergency spool engaged I will try simulating a total electrical harness failure. "Unplug it" and see what happens