From what you describe and the history the problem is still in the centering system. This diagram is from the parts book and here's a link if you want to zoom in or need to order something.
New Holland Parts Catalog Lookup. Buy New Holland Parts Online & Save!
www.messicks.com
I'll start by explaining how this works because anything loose in here can cause jerkiness.
- Bars 6 & 10 are connected to the bottom of your control handles at the front. At the back they are connected to the blocks 2.
- Control arms 2 are clamped (and keyed) onto on the control shafts of the hydro pumps. They directly control the oil flow direction and speed, thus steering.
- Shock absorbers 5 are meant to help dampen/limit jerkiness in the handles.
- Now the more complicated part - the bearings 1 are bolted into the top of the control arms 2.
- When assembled, the bearings 1 ride against the sides of the blocks 11.
- The angle of the blocks 11 position in the slots (angle when looking from the top down) in plate 12 controls the neutral position of the hydros so it stops and doesn't move when you let go of the handles.
- The plate 12 slides on bolt 25 at the rear and slide pins 8 via plastic blocks 9 at the front. Spring 14 returns the plate and system to the neutral position.
Clear as mud?
I think bolt 25 may be the one you said came loose.
Anything loose in here could be the problem.
I've had problems with the screws 23 holding the plastic blocks 9.
Also the angle of the blocks 11 sets the neutral, but they also have to be snug against the bearings 1. These are tricky to get set. It's best to have the loader up on blocks when adjusting them so you can see if the tires are turning while adjusting for neutral.
If everything looks correct, I'd want to make sure the key between control arms 2 and the pump shaft is there and in good condition.
This should be a good start.
