fld120 steering problem ! pls someone help me !

That is the only external adjustment. Keep in mind while making adjustments that you need to steer completely from lock to lock then back to center to see any change from the adjustment you made, otherwise you will think you made no change until later when you drive the truck and internals get seated from steering load.

 

Make sure your 5th wheel is lubed, dry spots can cause this also.

 

See, your doing all this messing around, taking things apart and just guessing. Take your truck somewhere and have the caster measured!

 

Sounds to me like a kingpin is binding up on you.

 

Well, for it's worth, I thank you for at least listening to me and getting your caster measured, I appreciate that. I am sorry to hear it isn't the problem, but at least now we know it is good. We just had a truck in for something like this a couple of days ago and we found the slip joint in the steering shaft was seized and causing the steering to be stiff and not return to center. The shaft needs to slide in an out a bit as the ujoints turn and the seized shaft prevented this and caused the problem. Simple check, remove the steering shaft at the input of the gear and just try to pull it out and push it in to see if it will move freely. I understand your frustration, I'll try my best to help out.