one thing with these creatures is the big bearing between the upper and lower drive unit will go bad and cause harder then normal steering. If you replace it you must put entire weight of machine on the ground before you try and readjust the encoder.

Swoop,

I have changed the tire out to a poly tire. I also noticed some resistance in the steering motor. The bearings seem a bit worn. I swapped that out with a used one in had on the shelf from another stock picker.

After changing all that out everything was working excellent (for me). So I put it back into rotation and let a novice operator take onto the floor. He immediately had several issues.

!. it would wrench out when he would turn to far to the right. this only happened if he was not in motion.

2. when this wrench came on and you cycled off and back on the steering would not move unless you had it in motion (forward or reverse).

I have checked all connections associated with the steering and have found nothing at of the ordinary. You mentioned before that I should take readings on the steer/tiller encoder. What are the readings that I should see when checking this?

Do you think this could be due to a bad bearing in the drive unit?

I appreciate the feed back.

Thanks.

yes i would look into the tire issue then
one other thing to consider is you are still dealing with an electronic controlled steering, it is not truly manual like the old units that used a cable to control the drive unit position so taking that into consideration you may not get an exact split in revolutions in the steering tiller between right versus left from center steering directions. Being it is still relying on the electronic signal from the wheel tiller encoder it may still be getting a signal to move the wheel, but taking the resistance of the drive tire and steer gearbox 'true center' position it is possible that it may not move the wheel exactly as you are turning the wheel/tiller.
My guess is the rubber tire is probably causing alot of your issue mainly because you said it turns fine when the load is taken off of the tire.

Swoop,

Thank you for the outstanding information. First off the truck is a manual steering truck. It use to auto guidance system, but was removed before we obtained it. I did take that into consideration with my troubleshooting. I found the auto system to not be an issue. Secondly, I did ohm out every wire in the mast cables. I read them at different lift heights and had no inconsistencies. I did not check the output signal of the encoder behind the steer wheel/tiller. One thing I did do though is disconnect that encoder and hooked up a new one I had on the shelf. I still had the same issue though. As far as the status of the steer module; I watched it as someone operated it and did not see the service light come on. I also checked all the connections associated with the steering on the distribution panel. I did not find any bad or loose connections there. And after reading the voltage output on each wire; it all corresponded to what the book was telling me. Unless I was misunderstanding it. But it does make sense that the poor connection could cause inconsistent revolutions of the hand wheel. I will have to check that again.

The truck does have a rubberized tire on it. All my other ones are poly. I will check the tire status on this as well.

Thanks for all the info. I will let you know what I find.

Sorry for this long post but before you just go slapping on a steering controller please heed the following, there are just too many things to consider before jumping to conclusions.

before you go replacing the steering module there are things that need to be known before a definitive diagnosis can be made
- is this a manual steering truck or a automatic guidance steering truck?
The reason i ask this is a manual steering truck has the steering encoder signal going through the dash display module and then in conjunction with the steering module it tells the drive unit which way to turn. With Automatic guidance steering everything is wired differently, it still communitates with the display module but the encoders are connected directly to the steering module.

- have you checked the wire harness cables going through the mast? according to the parts diagram there can be up to 4 cables, one of them deals with the steering system.
- have you checked the output signal from the steering encoder at the encoder, at each point in the wire harness till it gets to it's destination on the tractor unit? (this is the encoder behind the steer wheel/tiller)

-what is the status of the steering module when operating the unit? it has an led power indicator and a status or service indicator on it. If there is an issue with it the service indicator light will be illuminated the power on indicator light should always be on when the truck is turned on. This truck may also have a distribution panel connecting all the components from the platform to the base unit down on the tractor unit, there are many connections there that need to be considered as problematic.

The reason i ask these questions is because a faulty wire in the harness can cause an intermittent signal or a poor signal creating the inconsistent directional movement under a load in the one direction of steer.

One other thing to understand is the steering "feedback" encoder on the drive unit is only there to report the position of the drive unit so it can display that onto the display screen on the dash, it has nothing to do with the speed of the movement of the steering unit. Now the "steering encoder" (on the steering wheel/tiller) is what you need to be checking. This is like a tach generator and it generates a signal in positive signal or negative signal to report to the steering controller on which way the motor needs to move.
If there is a problem with the steering tach generator or its associated wiring that can indeed cause the problem you are having. The manual labels this as an encoder ECR1.
And last but not least the tire itself, if this has a rubber tire on the truck a rubber tire can cause all sorts of issues with steering, the rubber grabs the floor and puts a great strain on the steering motion and if it binds up too much it can make this very thing happen with the steering movement. Now generally you would experience this movement restriction noticed in both directions but who knows, it could be something going on with the shape of the crown on the tire (if it has any crown left on it). The wear of the tire needs to be considered as well) ;o)

So you have to more troubleshooting to do before you can make a decision on what to repair.
So don't just go out and buy a steering module without knowing the full picture first, they aren't cheap ;o)

Good luck

Steer module