Steering woes

[Thrawn]

Same truck I just did the rear work on, '01 RD 688, we had in the shop awhile back repairing a beat up fuel tank from an accident, while it was in here I replaced the power steering hoses due to them starting to leak pretty bad. After it was done I noticed some hard spots in the steering on occasion. I thought I still had some air in the system and kept working it, but it never cleared up. The driver said it's been doing it before I replaced the hoses. Any easy way to single out where the problem is exactly?

[Swishy]

this may help..........may not

cya

§wishy

Edited October 24, 2011 by Swishy

[slpwlker]

When I replaced my steering boxes I had 1 hard spot and that was if I turned left and went quick right it bound for a second then turned. Ended up having air in the right side box. for whatever reason it never bled out. Now it works better no stiff spots,only problem I have is it isn't as fast as I would like. I have never driven anything with 2 steer boxes before and I don't know if they are alittle slower then a single box or if there is still a problem still lingering. But it is drivable.

[Rob]

When I replaced my steering boxes I had 1 hard spot and that was if I turned left and went quick right it bound for a second then turned. Ended up having air in the right side box. for whatever reason it never bled out. Now it works better no stiff spots,only problem I have is it isn't as fast as I would like. I have never driven anything with 2 steer boxes before and I don't know if they are alittle slower then a single box or if there is still a problem still lingering. But it is drivable.

What you experienced there is typical of air in a hydraulic system. From basic physics it is understood a liquid cannot be compressed yet a gas can. This is what makes hydraulic systems work by the movement of fluid under pressure. The steering gear didn't actually "bind" in your scenario but rather the air in the system compressed until such a time as the pressure build was satisfactory enough to push the fluid though the rotary spool valve allowing the gear to have hydraulic assist.

Almost always a power steering system is open to atmosphere someplace above fluid level which is usually in the storage reservoir. This is where you add fluid and the there should be a vent in the cap, or lid. Typically when the system is first filled, the engine is started with fluid circulated by a positive displacement pump. The circulated fluid contains entrained air bubbles which eventualy dissapate through the reservoir vent. Foaming fluid is indicative of air entrainment in a hydraulic medium, and is not good due to shock loading of parts it can cause. Most large applications enlist a hydraulic accumulator to control and limit the damage this can cause, but most automotive applications do not.

Binding steering gear assemblies can be a multitude of things. Often overlooked in a system that is consistently ran low, or out of fluid is the wear on the internal valves, balls, rotary screw, (worm) or sector gear, (attached to pitman shaft). When these are run without lubrication they wear quickly internally and gall easily. This is especially true with TRW/Ross steering gear designs. The gear loading is tremendous is these gears. Double steering gears lessen the load each gear must carry, but they are usually incorporated only in heavy spec chassis. However, there should be no difference in the way the truck drives or behaves given one, or two steering gears. They are both actually actuated by the hydraulic medium of fluid. The mechanical effect serves to start the process by opening ports in the spool valve internal to the steering gear which then assists and reduces the effort needed to turn the wheels.

The best way to bleed a difficult steeing system is to leave the return lines from each steering gear slightly loose while allowing it to bleed at idle into a bucket. After the gear is satisfactorily bled, then move to the return of the reservoir. Usually it is a high spot in the hose routing that makes it difficult to bleed hydraulic systems as is the cause with hydraulic brakes also.

If you steering is slow it is either a function of fluid flow, or steering gear ratio. Hydraulic pressure has nothing to do with the speed at which you can turn the wheels; hydraulic flow does this. Hydraulic pressure is what factors in on how easy it is to turn the wheel. For instance a 27:1 steering gear ratio will turn the wheels much easier than say a 14:1 ratio, but it will take many more turns of the steering wheel to turn the tires through this reduction. Most hydraulic steering sytems operate at about 5-6.6 gallons per minute flow rate. The pressures vary by application with 900-2000psi relief pressure being common. Of course the higher the expected weight rating, the higher the pressure. It also takes less pressure to accomplish the task of turning the wheels with greater gear reduction through the steering gear.

Learned everything I know from Other Dog, with Randp's assist.

Rob

[slpwlker]

Both boxes are new, both pitman arms are new. Pump is 2 years and is the same or has the same pressure as the ones on a 2 box system. it is putting out 2200psi when you bottom it out. We'll get it figured out. just gets aggravating when i need to manuver fast i got to either get in a real low gear and keep the rpms up alittle and it helps. or push the clutch in and rev the motor to help turn. This truck is not factory duel box system. But Pete ran the vin and the new axle vin and came up with the solution for the duel boxes.

[Rob]

Both boxes are new, both pitman arms are new. Pump is 2 years and is the same or has the same pressure as the ones on a 2 box system. it is putting out 2200psi when you bottom it out. We'll get it figured out. just gets aggravating when i need to manuver fast i got to either get in a real low gear and keep the rpms up alittle and it helps. or push the clutch in and rev the motor to help turn. This truck is not factory duel box system. But Pete ran the vin and the new axle vin and came up with the solution for the duel boxes.

You do not have enough flow for the job you are asking of it. 2200psi is your relief valve setting and is adequate. However, the flow rate at the relief setting is considerably less than operating as some fluid is bypassed to keep the system from blowing itself apart. I would go with a larger pump with 1/8" longer gears, or vanes internally. Most power steering pumps are Vickers V20 series and are easily acquired aftermarket. This again has nothing to do with pressure, nor will increased flow detract from normal driving habits. The steering wheel will be a bit easier to turn rapidly no matter the loading.

I had to consult Other Dog only as Randyp was indisposed at the time to ensure I was accurate in my information relay.

That Other Dog, he's my hero you know.

Rob

[slpwlker]

You do not have enough flow for the job you are asking of it. 2200psi is your relief valve setting and it adequate. However, the flow rate at the system setting is considerably less than operating as some fluid is bypassed to keep the system from blowing itself apart. I would go with a larger pump with 1/8" longer gears, or vanes internally. Most power steering pumps are Vickers V20 series and are easily acquired aftermarket. This again has nothing to do with pressure, nor will increased flow detract from normal driving habits. The steering wheel will be a bit easier to turn rapidly no matter the loading.

I had to consult Other Dogonly as Randyp was indisposed at the time to ensure I was accurate in my information relay.

That Other Dog, he's my hero you know.

Rob

I forgot what the flow rate was. I know it was not a small pump. i think it was 6 or 7 gallons a min when they checked the flow might of been a tad less

[Rob]

I forgot what the flow rate was. I know it was not a small pump. i think it was 6 or 7 gallons a min when they checked the flow might of been a tad less

On a dual steering setup you do not need exactly double flow rate as a single gear but about 70% additional is adequate.

Couldn't make contact with either of my heros so hopefully I'm correct in my analogy.

Rob

[bobo]

whens last time king pins were greased? bobo

[slpwlker]

whens last time king pins were greased? bobo

Every week when I am under a load. I grease the whole truck. If I just run empty, light, or sit I'll wait till I get a heavy load which is 99.9 % of my loads

[bobo]

I had an older fella offer me a job not to long ago, cause I greased my roll off bed, as he load the box on the trailer. Said he cant remember the last time he saw a "kid" with a grease gun! even told me he'd buy the RB off me and let me drive it! kinda made me feel funny inside!

Ive seen it before where the grease hardened in the adj. king pin and made it fell like power steer was dead. bobo

[Rob]

I had an older fella offer me a job not to long ago, cause I greased my roll off bed, as he load the box on the trailer. Said he cant remember the last time he saw a "kid" with a grease gun! even told me he'd buy the RB off me and let me drive it! kinda made me feel funny inside!

Ive seen it before where the grease hardened in the adj. king pin and made it fell like power steer was dead. bobo

Yes but they typically don't do that if the joint is exercised occasionally. Let a truck sit a few months without use and the soaps that thicken oil to make grease start to harden.

Rob

[slpwlker]

This when it was a single box was faster I just had problems turning the floats at a dead stop off road. or depending how heavy I was on the steers when i picked the pusher up. Empty It turned alittle better but it gave you a work out esp trying to manuver in a tight spot and turn turn turn ugh

[rhasler]

Thrawn,

if it's binding every 90 degrees look at the u-joints in the steering column, if it's every 180 degrees check the timing on the steering shafts. Another place that sometimes causes a bind is the carrier bearing on the steering shaft.

Here's a bulletin that may help. The information is specifically for a CV chassis, but the principles should carry over.

And another thing, is that a baby smoking a pipe or a leprechaun?

SB 412-007 Steering Shaft Troubleshooting - CV713 - Equipped with Sheppard M110 Steering Gear.pdf

[Thrawn]

Light bulb went off when you said check the steering shaft timing. We had it apart awhile back when it was broke down for something else and I had to rob the U-joints for an emergency repair on a truck elsewhere. I'll check that out.

Looks like a real pipe, dunno, seen it on the internet and thought it would make a good avatar pic.

[Thrawn]

Brought the truck in the other day to check out the steering shart and the steering was working fine, checked the alignment of the joints anyway and everything seemed lined up ok. Must've been air that finally just worked it's way out.