I have a 1978 John Deere 450c dozer that once had a backhoe attachment that I just picked up at an auction. I have several, but likely related issues. First the dozer seemly has no brakes, neither the foot brake or either lever engages. Both adjusters were very tight, possibly to the point of being at the end of their adjustment stroke. The foot pedal bottoms out on the firewall and the levers pull all the way back to a mechanical stop with no resistance. Next, I unhooked the brakes all together to ensure the steering valves were properly dumping pressure when actuated. The steering clutches do not release in either forward or reverse, which I am assuming might have worn the brakes out. I pressure tuned the HLR transmission and everything works nice except the time of shift from high to reverse, avg. 2.78s, the time from reverse to high averages 1.73s, average pressure is around 175 psig. I changed the transmission fluid and filters as well as cleaned the suction screen, which was terrible, looked to be full of either clutch fiber or fiber from a collapsed filter long ago. Is there a pressure test point in the steering clutch circuit? I am trying to understand the most likely culprit.
Sounds to me like the steering brake bands may have no more material, which is why you have no adjustment left on the brake band star wheel. There is a rate of shift adjustment on the right side of the transmission case. But before any rate of shift adjustments are made, the HLR Clutch "MUST" be properly adjusted. Did you adjust this so that the pressure rises 5 psi when the clutch pedal is depressed approximately 1/2 - 3/4 of an inch?
Thanks for the response. The pressure is adjusted per the manual, I am getting the 5 psig rise with 1/2” pedal movement. I don’t think I want to adjust the needle valve as the R to H timing is in spec, I am assuming the H to R timing being sluggish is due to leaking seals in the reverse clutch pack. I will run it as is for a while if I can get the steering clutches to release.
Update - I pulled both the left and right supply pressure lines from the HLR transmission to the steering clutch housing and checked the pressure. It was dumping pressure properly but only after stroking the levers around 6 inches, I readjusted the spool valves to be in spec and dump the pressure at 2.5 inches. Now the steering clutches disengage but not fully. I tightened the brakes as tight as I could get on each adjusting nut, and have no resistance on the right lever and minimal resistance on the left, pedal still bottoms out. That being said, I am confident that the brake bans are worn completely out and the clutches are pasted their prime. I will tear it down and change both sides.