M54A2 power steering question

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My power steering is all of a sudden getting hard to turn and then better and then hard again. No major leaks or anything on the outside. Is there a filter or anything in the system besides as you pour into the resivoir? Thanks in advance. I'm not even sure what is in the resivoir I think power steering fluid and oil possibly mixed?

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do you have the old style large steering box under the hood? or the upgrade ross steering box on the outside of the driver side of the truck frame under the front fender?
Under the hood.IMG_20200326_173955500.jpgIMG_20200326_173918722.jpgIMG_20200326_173943876.jpg

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msgjd

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You have the original (old-style) Ross system.... They can be a bit cantankerous at times.

Without digging thru my TM's, if memory serves me right there is no filter on these units other than the fill screen, as you saw... But I do remember the LO's on these trucks with the old-style Ross boxes require SAE10W motor oil in the steering reservoir, and also SAE10W in the steering box... 8-1/2 quarts in reservoir , 2-1/2 quarts in gearbox if I recall correctly. I believe a free download of the M39-series LO is still available via SB member jatonka35s.com website. (and it's also available right here on SB in the TM section tab, under 5-ton)

If the old-style PS gearpump shaft seal is going bad, you would lose fluid and not see any leak. Your engine oil level might go up, depending if engine burns or leaks oil... If yours has PS fluid or ATF in it, the fluid might be too thin for the pump shaft seal to hold it, and also too thin to keep adequate pressure when warmed up (especially in an old pump) for the steering to work well.

Of course you could also be having a problem with the diverter vane (or whatever it's called) inside the PS unit on the gearbox. But usually when that's failing you are able to steer one way okay, but in the other direction it steers really hard. Thus, it sounds like that vane is not your trouble.

Your steering hesitating and then going again is a symptom of low oil level, among other things. Re-check your fluid level.
Eliminate the simple things first. Also, I would drain whatever is in that reservoir and also drain what's in the steering gearbox. Refill with SAE10W. Since you're in Texas and perhaps the PS pump is worn, you might think about trying SAE20W, if you can find it. Anything you want to try with steering is at your own risk, I'm not assuming any liabilty here.

I have old farm tractor hyd systems calling for 20W summer, 10W winter. These old hyd systems were built for motor oil and therefore should remain so. I hope your problem is the simple one.
 
Last edited:

Slate

Active member
Steel Soldiers Supporter
532
166
43
Location
Ozona Texas
You have the original (old-style) Ross system.... They can be a bit cantankerous at times.

Without digging thru my TM's, if memory serves me right there is no filter on these units other than the fill screen, as you saw... But I do remember the LO's on these trucks with the old-style Ross boxes require SAE10W motor oil in the steering reservoir, and also SAE10W in the steering box... 8-1/2 quarts in reservoir , 2-1/2 quarts in gearbox if I recall correctly. I believe a free download of the M39-series LO is still available via SB member jatonka35s.com website.

If the old-style PS gearpump shaft seal is going bad, you would lose fluid and not see any leak. Your engine oil level might go up, depending if engine burns or leaks oil... If yours has PS fluid or ATF in it, the fluid might be too thin for the pump shaft seal to hold it, and also too thin to keep adequate pressure when warmed up (especially in an old pump) for the steering to work well.

Of course you could also be having a problem with the diverter vane (or whatever it's called) inside the PS unit on the gearbox. But usually when that's failing you are able to steer one way okay, but in the other direction it steers really hard. Thus, it sounds like that vane is not your trouble.

Your steering hesitating and then going again is a symptom of low oil level, among other things. Re-check your fluid level.
Eliminate the simple things first. Also, I would drain whatever is in that reservoir and also drain what's in the steering gearbox. Refill with SAE10W. Since you're in Texas and perhaps the PS pump is worn, you might think about trying SAE20W, if you can find it. Anything you want to try with steering is at your own risk, I'm not assuming any liabilty here.

I have old farm tractor hyd systems calling for 20W summer, 10W winter. These old hyd systems were built for motor oil and therefore should remain so. I hope your problem is the simple one.
Thank you. I have never looked at fluid level except what is in resivoir. Maybe the gear box could be it. I have not driven this truck much in several years and using it to fight grassfires it has been a lifesaver lately. With the steering becoming Arm-strong steering it is becoming a pain. I will get some fresh oil tomorrow and check it out and get back to post in the next day or so. Thanks again.IMG_20200515_203039104.jpgIMG_20200515_203001981.jpg

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Slate

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Lo says fill resivoir to only 3/4 full it is almost to top.

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Slate

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But the gear box when opened had maybe 20oz in it. I think we have found the issue. Now to fill it up and see if we ruined anything. I Know I know read the TM and the LO.

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Slate

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And imagine that lubed properly she turns again!!! Problem solved. Thank you gentlemen. Gearbox was empty and filling everything I could see worked good untill that one part, that looks like it is part of the system, didn't get lubed. I have a LO now and everything else seems fine.....for now.

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msgjd

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upstate ny
glad it was the simple problem ... my M51 has the "almost-impossible-hard-steer-one-way" problem... one of these days I will tear into it, meanwhile it's relegated to off-road work only
 
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