Allis Chalmers HD 21 Dozer torque converter proble

I have an early 50s Allis Chalmers HD 21 Dozer with a torque converter issue. The torque converter is the old style which uses diesel for its fluid. The Dozer was working good until parked for several years runs great now but has no push power at all barely moves back and forth under its own weight. I have changed the fuel filters and I know the fuel in the tank is good and clean. If anybody has any ideas of where I can start I would really appreciate it I have looked on the Forum for other postings I am having trouble finding the mentioned restrictor to make the fuel pressure in the torque converter stay above 30 PSI I do not have a fuel pressure gauge if I can share some pictures with someone who can maybe give me a hand locating what I'm looking for I would really appreciate it. Thanks.

Edited by Shaun - 17 Jul 2025 at 5:58pm

Thank you very much I will try throwing a few more Jerry cans in it and see what happens if it makes a difference

make sure you have fuel pressure!  any air intrusion or loss of diesel in the converter makes a big difference.  on my hd20 it runs about 60 lbs.  my 20 uses a separate cooler for the fuel, but i think 21s were built into the radiator.  follow the converter cooling tubes up to the radiator and the restrictor should be in the fuel return line near the cooling pack, but really only need to bother with it if you have excess pressure.  sounds like you have very little or none.  if fuel has leaked out  you need to have the clutch engaged and engine running for a couple minutes before the converter will refill.  your symptoms say low pressure.  cable control on rear of machine is also driven by converter so it will affect movement

Edited by CAL(KS) - Yesterday at 3:49pm

And this does have a separate cooler for the diesel off to the side of the radiator for the coolant in the engine