Clark 668c winch issues

[Glenbrae123]

Hi there,
I have a clark valmet 668c with some winch problems. 
When we first Brough it, the winch wasn't working at all. And if you tried to drive it anywhere when it was warm it would loose drive. So we cleaned out the pressure regulator valve on torque convertor and now the winch will free spool and it doesn't seem to loose drive anymore, however we haven't taken it for a good run yet. The winch brake works good as well. It just does not pull in under load, but will pull in the rope with nothing on. Ive checked the trans pressure today and have 250psi at high idle. 
Just wondering if anyone has run into something like this before and has an easy diagnosis. If not what should be our next step.
Thanks