Well i need some other brains to mull this one over for me and im hoping my own will pop into gear while typing this.
Ive had my d31p-18 for years now. It has had fussy steer pedals at times and over the years ive redrilled worn out control rod link yokes to oversized tighter pins and restored the consistency. My steer spool cam follower rollers were all sloppy and wallered and thats all pretty well sorted out now. The quirk its always had was itll engage firmly and go forward from the start even stone cold, but not going in reverse for quite a while. When youre getting close youll see a track start to tense just a hair but you sit and wait a while longer.. its like someone riding a clutch so they dont roll back on a hill.
If you went forward about 20 feet first itd go in reverse, or if parked against something, you had to let it warm up a long time and revved way up before itd eventually "catch" reverse. Once it catches bam youre off, full power in either direction forward or reverse, it pushes trees and skids them no problem. Once reverse is working, itll shift forward and reverse and steer at idle. But in the beginning it wont engage reverse at all, from idle to full throttle
It was getting fussy to steer the past season so i went in to do some maintenance. Id be slamming the pedal to the floor and itd drive thru the brakes without the clutch uncoupling drive power from the track you wanted to stop. Smash pedal down to the brake and itd go straight.
To turn i had to go to neutral, push pedal all the way down then engage gear for it to turn correctly. Pivot turns only from a stop, no gradual ones. Both sides same way to the same degree. I took the slop out of the control rods under the floor and then the steering was gone. Itd go forward with full engagement but not steer or reverse at all after that adjustment.
I read the theory of operations a few times and went into the steer spool block, the fwd reverse speed and inching valve block, and the modulator valve, which sets pump pressure via a counterbalance spool. I didnt find any catastophe but did replace a few o rings just because they were nicked or hardened. Put it all back together and i set the steer spool rollers so they just barely spin but are nearly touching the spool tips.
My pedals have full stroke to depress the spool plungers and i set the brake bands to engage at a comfortable stroke and equal to each other. Before they were grabbing way down low at the end of the stroke so i tightened them to advance engagement up higher. Not by a lot, theres plenty of slack and you can tell by exhaust note they arent hanging.
Next startup it wouldnt really engage forward or reverse.. it was doing the almost shift into gear thing that normally only happens with reverse while cold. I dont have an 1/8" npt to jic fitting to test port pressures yet but reasoned out that this is low pressure in the control circuit, since it takes pressure to engage the fwd/reverse planetary and to fill the steer slaves which push the clutch yoke to uncouple power to either final. So i shimmed the modulator double spring with a washer.
It now goes forward and reverse from cold equally well, which is the best reverse engagement it has ever had and that suggests i am going the right direction raising pressure. when i try to steer it will occasionally steer, but mostly it just stops the machine completely without any steer action. both tracks will stop by depressing one pedal and im starting to get confused. If the steer slaves were vented of pressure the clutch springs would apply full coupling power. I know the clutches are good because it pushed trees out last week with full power. Is it possible i have the roller follower wrong on the tips of the steer valve spools?
I dont have any external leaks. I changed the trans fluid years ago and had no trash, strainer was pretty clear. Oil still looks good n clear on the stick, never heard any bad noises. Im kinda chasin my mental tail on it.
Thoughts?