New owner, old 960

[HughF]

So, I bought an old 960 from a tractor dealer here in the UK... £6k delivered, which seemed the going rate for a skid steer over this side of the pond. Tyres are good, bucket is usable, starts and drives. 3800hrs.



It spent it's early life driving a road planer so has Hi-flow hydraulics on an electrically driven solenoid valve under the footplate. Regular 3rd spool valve outlets also piped up:



Within 24hrs of taking delivery I had got it sunk up to it's belly in my field, which then necessitated some work with a tractor, a tirfor winch and a few evenings to haul it out:
I have since purchased some McLaren over-tyre tracks for it.




I've fitted a new fuel filter, sorted out the wiring which was a mess, and given it a general going over. Seems like an honest machine. Hoping to put it to good work in the confines of my barn where I can't get my tractor.

 

[HughF]

OK, so using this a bit and I've discovered a bit of an issue. It seems to lack power in forwards when it gets warm. The stick come up hard with quite a bit of resistance, so I'm not sure if it's drive motors or pumps that are the problem. It still has tons of power in reverse.

Video showing the issue:



I suppose I need to get a pressure gauge on the lines to the motors and verify I'm getting 4500psi? I notice that the charge oil filter hasn't been changed, would that cause the issue?

I'm mechanically very competent but haven't had any experience of hydrostatic transmissions before, skidsteers being rare as unicorn fart here in the UK

 

[Firefighter]

Try the filter, the motors may need rebuilt, if the drive is ok in reverse but not forward it would seem as
an issue with the motor, if its in both directions, then it probably has damaged or scarring on the valve plates
both the pump & motors would need disassembled, easiest way to check the reverse is back up against a stationary object or wall etc,

 

[HughF]

The way I see this:

1. Pressure test charge pump
2. Pressure test forwards/backwards pressure on both pumps (to validate relief valve performance)
3a. If above fails, swap relief valves between forwards/backwards and see if the machine now has power in forwards and lacks power in reverse
3b. If above passes, look at the motor being the issue.