Steering slack

[fraser8]

I have some play in the steering of my 72 Prevost. When you are driving you are constantly going back and forth with the steering wheel (about 4 inches) at center. The steering box is tight and OK the slack is in the power steering. The power steering assembly moves about a 1/2 inch before the rest of the pitman arm moves. Can I tighten this so they move in unison and take the play out?  I've put an arrow where the play is/

[TomC]

I had a similar system but with air powered steering.  It was alright in town, but wondered so much at freeway speeds, it was alot of work to drive it.  I finally replaced the whole steering with Sheppard integral power steering.  Went from 8 and 1/2 turns lock to lock to 4 and 1/2 turns lock to lock and now is finger tip steering that can turn as fast as you want.  You may want to consider the switch also.  Good Luck, TomC

[Lin]

I have had this problem for a while also.  Aside from the roughly 15 degrees of play in a power assist system, mine had other problems in the steering column.  We are now replacing the steering column and making sure everything else is tight.  There is a possibility of internal leakage in the assist piston.  Once I have it all right, I will see if I like the way it drives.  If not, I too will switch to integral power steering.  So, I would say, if you don't mind diddling around a bit to see if you can make it acceptable, do it.  If you want to save the effort, go with the upgrade.   

[fraser8]

Is there a way to adjust the length of the power steering assembly that makes it longer to take up the slack. It's a Garrison model.

[gus]

Fraser,

I know nothing about Prevosts but if you have power assist steering, which it appears to be in the tiny photo, you have manual steering when driving on straight roads. The hyd cly boost only works after you turn the steering wheel a certain number of degrees.

This means the steering slack is in the manual steering box at the axle and not in the power system.

Your maintenance manual should tell you how to adjust it for slack. I know how to adjust GMC steering but not Prevost. I had the same problem and adjusted it out so that I now have about 1/2" at the steering wheel rim.

[fraser8]

The steering box and the rest of the steering is tight, the power steering assembly on the steering shaft (that attaches to the pitman arm) is loose. I can move the power steering back and forth on the shaft. What happens is you must turn the steering wheel a few inches before the power steering assembly moves down and pushes the steering arm. Click on the picture to enlarge it.

[gus]

Fraser,

Forget everything I posted. Your system is nothing like mine.

Thanks for the info on enlarging the photo, always did wonder how to do that! I had always clicked the photo itself rather than the .jpg title.

[Sojourner]

About the power assist steering.....steering play will be about 2.5 inches at the steering wheel which is normal after everything's is adjusted.

To get less play than that is to go for integral steering box.

Why is integral less play than assist steering?

First of all you need to know that a hydraulic control valve (picture) (integral has it within the box) is what applies oil pressure to either versions...a assist (boaster) cylinder or an integral's piston.
BTW...thanks for including a picture of a Hydraulic Control Valve.

The power assist system has a hydraulic control valve and a slave cylinder after the steering box which is about 12 to 1 ratio.

The integral power steering box does not a slave cylinder but instead a internal piston before the gear ratio will reduce the plays.

In other words, soon as you turn the steering wheel 1/8 of an inch it applied oil pressure to the integral's piston.

And the power assisted steering with slave is no longer in vehicles since early 80's.

FWIW

Sojourn for Christ, Gerald

[Lin]

Is it possible that we're not all talking about the same thing.  Sam Caylor told me that power assist had 15 degrees of free play.  That would be about 2.6 inches of play on a 20 inch wheel.  But is that really steering free-play or is it just the space it takes to engage the assist piston from one way to the other.  Does that mean that while moving in that 15 degree range you are merely using manual steering, or does it actually mean it is genuine free-play and there is no control within that range? 

[fraser8]

With mine it is free play. You move the wheel 15 degrees or more before the hydraulic control valve moves down the shaft and is tight and activates the ram. When you are driving you constantly move the steering wheel back and forth to compensate for the control valve sliding up and down the shaft.

[Sojourner]

fraser8...all cars & trucks before the 60's had the very same system you have. It was an optional power assist steering system. After customers driven a short time, they be complaining for wandering. Dealers check it out for safety, with ok and said to them "It normal to wander...you get used to later" Been there because I was one of their mechanic for piece work pay.

This play is a must have to control the oil valve-ing inside of Hydraulic Control Valve assembly that is attach to the drag link's end of the pitman arm.

MCI-8 or older have power assist cylinder too but the Hydraulic Control Valve is attach on input shaft side of steering box. It still wanders too.

Now since about 48 years, all vehicles are integral type steering. Thanks goodness.

FWIW

Sojourn for Christ, Gerald

[boogiethecat]

Your steering is almost the same as the one in my Crown, and it is totally adjustable, and also very easily rebuildable.  Call the company 800-203-1894 or
INFO@GARRISONMFG.COM   Mine is a  bg211 series but yours looks a bit different.
The deal is that either your valve body needs a rebuild (simple o-rings to be replaced) or your steering pump isn't pumping.  The way it's supposed to work is that with the engine off there will be some slop, which is the control valve doing it's thing.  But with the engine running the slop gets taken up by the valve and ram doing their job, and if properly functioning there will be very little slop with the engine running.  Certainly not as much as yours, which sounds just like mine was before I rebuilt it.

Also, adjusting these is commonly misunderstood as the proper adjustment of one is totally counter-intuitive.  The slop in an "engine-off" unit should only be measured in the thousandths, but not in inches...
Anyway if you need more info, email me
CHeers
Gary

[fraser8]

Thanks for all the help, it gives me food for thought