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77newell 08-02-2010 12:41 PM

Steering solutions
Here is an overall history of steering improvements for my 77 coach with almost 200,000 miles on it.

First symptom was the need to bump the steering wheel in the direction of needed correction and then bump it back to center almost immediately. The solution was to loosen the adjustment on the gearbox as it was tight enough to stick. The gearbox is a Ross. I had the alignment and mechanicals all checked OK.

Second symptom was just a feeling of ambiguous response to steering wheel inputs, OK with small inputs but less responsive with bigger and faster inputs. Newell told me that if all the rod ends are tight then maybe I would need a new gearbox. I got lucky when during some engine work the steering fluid reservoir was emptied and then refilled with Gunk power steering fluid and voila much better steering. I had previously used ATF with a 7.4 viscosity and found out the Gunk has a viscosity of around 8. I drained some of the new fluid and added 48 oz Honda/Acura fluid with viscosity of about 11, steering is even better.

Though TRW says you can use engine oil up to SAE 40, do not mix it with either ATF or power steering fluid as it will result in tar balls. Mixing ATF and PSF is OK.

Jon Kabbe
77 Coach with Civic toad

Richard and Rhonda 08-02-2010 02:40 PM

Thanks Jon,

That is very good info. Like you I have been in pursuit of the best steering possible.

I had an "alignment" guy who supposedly knew what he was doing tighten the gearbox without telling me. It makes the coach steer very badly with exactly the symptom you describe. Did you adjust using trial and error, or some other technique.

TRW says the correct way is to remove the box and adjust the screw to achieve a given torque on the input shaft.

Others have said to remove the drag link and adjust to just remove the play.

How did you do it?

Using heavier PSF is something to try. Did you notice any difference in the "on center" steering as well?

77newell 08-03-2010 02:38 AM

Richard: the adjustment was done by Champion Frame and Alignment near Chicago and I wasn't present when it was done so I don't know how it was done. However they did it was very quick as the time charge was minimal. Based upon that I can't see how they disconnected anything. My suspicions are that they had someone gently rock the steering wheel while loosening the adjustment until slop began to appear, but that is just a guess.

Since the adjustment was made the wheels tended to return to center pretty well, but I would say the wheel has better feel since the Gunk was added. The steering feels somewhat tighter, maybe slightly heavier since the Honda ATF. It is so cool now to go for awhile without even noticing I'm steering since the wheel movements are so much smaller than they used to be, just tiny movements of the wheel create steering.

If you need more information or specificity let me know. I'm happy to share what I've experienced but realize I'm no expert (I'm less than 25 miles from home)

77 Coach

Richard and Rhonda 08-03-2010 11:34 AM

Thanks Jon

James Tuckness 08-03-2010 04:19 PM

Mechanical adjustment of steering gear is used to "set center" the gear. This is when the gear touches and slightly binds in the center position. This keeps you from having to constantly chase the ball with minor adjustment of wheel position. Power steering fluid for each type of system is specified by manufacturer, use only what they specify. Any other fluid will not work in the system properly. To remove "slack" from steering gear loosen the lock nut and tighten set screw in to take up slack only. There is a slot for a screw driver in the set screw because the force to set the slack adjustment is so small no other tool is needed. Usualy it is a small adjustment 1/4 or 1/3 of a turn will remove slack, another term for adjustment is "high centering of the gears" they just need to touch in the centered position no tighter. Steering box rebuilder instructed me on how to adjust centering on the coach. He also directed me to install heave "tube" grease in my manual box. The seals dry and shrink causing the box to lose gear oil and run dry. Grease will not run out and will not affect operation of box. My Garrison system had ATF in it when I purchased the coach. Steering was not smooth in operation. Proper fluid solved this problem, shake and some "shimmy" in left turn was caused by valves opening and closing on a fluid that was thinner than the proper fluid. Viscosity has a large affect on flow of fluid in system.


71-30" manual steering box with Garrison power steering system.

GORDON HUMMEL 08-04-2010 12:53 AM

Is it possible some caster was added? That would explain the quicker on center filling& tighter feeling but not the quicker response. All my previous Gas motorhomes were set at the Max caster setting & back in the 80's when I went to the new wider 70 series Pilots, even more was needed!
Just my 2 cents

Richard and Rhonda 08-04-2010 12:01 PM

Yep increased castor will do that. However changing the castor is not for the timid. You are not supposed to shim the axle the way big trucks do it. The way to change the castor is to rotate the eccentric bolts that the radius arms pivot on. The bolt heads are tack welded to the frame to prevent them from rotating. Plus the nuts for those bolts are hidden in the generator bay. The nut is 2.25 socket size, and torqued to 750 ft lbs.

You have probably figured out by now that I have played with the castor on mine.

Castor might have changed but in my own experiments the tightness of the gearbox is a dramatic effect compared to a change in castor.

77newell 08-04-2010 05:04 PM

Steering Solutions
Hey all: great discussion. No caster was added to my 77 coach by Champion. If you look at the bolt heads that secure the front end of the tubes running forward from the front axle you will see arrows. My top bolt arrow points to the rear and the bottom points toward the front. This is the maximum caster this system will generate.

According to TRW for my HFB64 steering gear ATF, power steering fluid and engine oil up to SAE 40 are all approved. They clearly advise that mixing fluid types can produce big problems. However, for clarification I checked with Valley Truck Parts, the local experts on steering gears, and they said it was OK to mix ATF and power steering fluids, but don't mix either of those with engine oil as tar will result.

Given the inexpense and near zero risk of trying the higher viscosity Honda PSF I decided to give it a shot and it did make a difference.

I agree that adjustments take very little force and that is were most people go wrong and produce the kind of sticking or hanging up that I was experiencing. On this gear tighter is not necessarily better and small adjustment carefully tracked as someone above suggested is what I would do if future problems develop.

Given the sloppiness of reaction to large and/or fast steering inputs that had occurred I wondered if the supply pressure was dropping at the higher volume required for these steering inputs. I suspect dropping pressure due to insufficient supply would also produce the symptoms I had but after the surprize following the Gunk addition I decided to try higher viscosity fluid prior to the far more complicated and expensive process of checking dynamic supply pressure.

77 Coach with Civic toad

77newell 08-08-2010 04:27 PM

One Final thought on the steering improvement following the addition of Gunk PSF noted above. The Gunk contained a "conditioner" that could have improved the performance of the seal on the actuating piston in the steering gear. I'm still trying to reason out whether some leakage through the seal would be better or worse with small steering wheel movements versus bigger faster ones. Just a thought

77newell 09-22-2010 07:30 PM

Yesterday I took a short trip in the coach and noticed the steering was more precise and reactive than previously. Therefore I suspect that the improvement in steering performance with the addition of Gunk PSF was due to the "conditioners" not the higher viscosity. Otherwise there is little to explain the improvement over time with no other changes being made recently. If this is true, it would suggest that the internal seals on the steering gear are not sealing well due to age and I'm due for a new gear sometime in the not real distant future when the "conditioners" no longer are effective in helping the seals swell up. An overhauled gear is about $750 plus labor (if I don't do it myself) so it's not a hugh expense.

1977 35' coach with Civic toad

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