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Power assist Parts


Tony S
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I have noticed that there is some play in the ball end of my pitman arm at the power assist valve. I thought I saw the sleve that the ball sits in somewhere from one of the parts suppliers but I can't find it. The power steering works and there are no leaks so I don't want to replace it . Although the ball on the pitman arm looks like it isn't replaceable it looked like the socket end was brass or bronze. Can the repair be done with out removing the pitman arm from the box?

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  • 2 weeks later...

The play in the pivot is about 1/4 inch. Looking at the parts exposed in the link it looks like the spring would have a lot of tension. If I wiggle the front wheels I can see the pivot on the pitman arm and the control valve is moving back and forth about 1/4 inch.

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I'm not all that knowledgeable, but here's my take:

Power steering is an add-on option, I don't think anything changes in the steering column or box. Basically a pump, a hydraulic control valve (with pitman arm attached), and a hydraulic power steering assist cylinder are added; on many cars a manual steering shock absorber is replaced by a power assist cylinder, but in looking at the parts manual, it does not appear that manual-steering Avanti's used a steering shock absorber.

The power assist cylinder (1551562) can push or pull to assist the wheels to turn (by pushing or pulling on the bellcrank), depending on whether you are turning right or left, but something must tell it which way you want to turn. That's the (1556068) valve attached to the pitman arm, with that valve being operated by the "pivot ball" you reference as moving... the ball has to move to cover/uncover the proper hydraulic ports to direct fluid pressure to either push or pull that power assist cylinder rod (with force in proportion to the resistance the wheels offer to being turned and the input the driver makes by turning the steering wheel).

Think of that pivot ball being like the lever of a kitchen sink faucet, which can give low or high flow (force) and either hot or cold water (analogous to direction), and the lever must move in order to control those parameters.

So, movement of that pivot ball would be normal, especially if it is pushing against hard resistance (like when the wheels aren't rolling and you turn the steering wheel).

Don't be concerned about movement, do be concerned about fluid leakage.

Edited by WayneC
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Thanks for the insight Wayne. I understand the concept but what I am talking about seems to be "slop" between the ball and the bushing. By the diagram it would look like there is always some spring pressure against the ball. By the looks of the spring it looks like there should be some moderate resistance to the ball sliding back and forth. I can take either wheel and hlod it at 3 and 9 oclock shake the wheel from left to right easily and the only thing moving is the ball on the pitman arm in the bushing. the rest of the front end is in good condition with all new bushings. i think I may go to a ford site and snoop around since Ford has millions of similar systems on the road.

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