Hope I am not too late, I had to contact the guy I know with experience and a service manual on the Allis 21 you have.
I have a question for you on the steering. To test the clutches you will have to have the machine moving and pull down on both levers and not apply the brakes this should stop the machine, if the steering pump and hyd system is working properly to the steering clutches. If it does stop then a simple brake adjustment is in order. There are two plugs near the front of the rear end one for each side just off center towards the outside of the machine. The plugs are towards the front of the steering brake cover which will require removal of the seat and sheet metal. The plug should be 1" to 1 1/2" round with a hex bolt on top[. Once the plugs are removed the adjuster for the brakes will be under the plug. Machine must be running and in a gear to adjust. Place it in 1st and move your direction lever to forward move some the move the direction lever back to neutral, this will release the parking brake and you will be able to adjust the brakes. Spec call for snug then back off 1 and 1/2 turn, makes them rather tight on a good shoe you may need to go an additional 1/4 for smoother operation. You have a really tough dozer it has one of the best transmissions of the day and still stronger than a same size Cat. Hang on to it!
Hope this helps, if you have further troubles post back with your serial number one of us will be able to help.
Hello again DLC,
Sorry to hear the adjustment did not cure the problem. We will work this out. Seeing that the control valves move in and out is good. There is a seperate pump for the steering other that the main hydraulic pump. I cannot access the information at this time, I will get back to you as soon as I can. When will you be able to get your tech out again?
The brake bands will be a big job.
Thanks for the accept!