M51A2 hydraulic power steering problem ross hydrapower

[rustystud]

There should be gear oil in the main body and hydraulic oil in the power piston and control valve. It appears your seals gave way and the hydraulic oil mixed with the gear oil. You know how the water got in. You will need to completely rebuild this unit. Be very careful removing the power piston to prevent damage to the sealing surfaces and the same goes for the control valve section.

 

[Robo McDuff]

There should be gear oil in the main body and hydraulic oil in the power piston and control valve. It appears your seals gave way and the hydraulic oil mixed with the gear oil. You know how the water got in. You will need to completely rebuild this unit. Be very careful removing the power piston to prevent damage to the sealing surfaces and the same goes for the control valve section.

I started to clean out the gear box, using straight diesel and small paint brushes. Lot of stuff came out.



Also took off the power cylinder. The connection to the gearbox did not look that great (left) compared with the one from the original box (right). Inside and the higher disk looked similar good though. Everything moved smooth as well.




Going for some new seals tomorrow. Will clean out everything once more, then carefully get rid of the diesel with some very hot water and then compressed air. Put some fresh oil on top of the bearings and other moving parts, then start put things together.

Rustystud, what confused me when replacing all oils 5 years ago is that according the lubricating TM ...12, the steering gear box and the power steering itself use the same oil. After some discussions here, I followed that and filled both with high quality straight W10 oil. Maybe the donor truck had two different types of oil.

Seeing the difference between the power pistons and other parts, is it an idea to combine the two boxes into one, putting the power cylinder of the old box into the new box, or is it better to keep the set together, and just clean very thorough and replace rubber seals?

Another difference is that in the original box, the Pittman arm moved freely in lateral direction, that is, jumped out of the grove of the cam and I could take out the cam. In the new box, the Pittman arm does not move laterally freely (I did not use force). I could not take out the cam. However, the Pittman arm stayed in place and the cam moved outwards when turning, so it is out of alignment as well.

I have to study the TMs carefully to figure out how to re-align all components so it will work again before putting the box back. Any suggestions?

 

[rustystud]

First off if you can get your hands on the correct manual that would be great. It's "TM 9-8615" Ross Steering Gears. Second there is two oils used. Gear oil in the main body and hydraulic oil in the pump and power piston and control valve. I know that sounds weird but that is how it was designed. Modern steering gears just use hydraulic oil for everything. Now the pitman shaft must have NO movement. It just turns about 60 degrees. If you can take the shaft and move it up and down at all the bushings are bad. The allowed movement is about 0.0005" ! That's half a thousandth ! The manual goes into great detail about refitting a new pitman shaft. It is a royal pain ! So if the other gear box has a good pitman shaft and bushings then use that box. If I could I would post the whole manual. As it is it takes me about ten to twenty minutes to upload a single page. It is OK to use the best parts out of each box.

 

[Memphisdoug]

Another Steering Problem with a M51A2

Started a new topic for my problem.