Outer Limits 4x4 Board

hello,
I have got a problem with the power steering on the hilux which seems to lock up after a couple of minutes of working. The hilux is a single cab 4x4, v6 conversion, lifted and running 37" wheels. We have had the pump rebuilt, changed both oil lines, changed steering boxes. When the steering locks up with load on the wheels, you can jack up front end and steering seems to be correct again. We have checked rod ends, swivel hubs which all seem to be fine when there is no load on them. Front locking hubs were disengaged also.
Has anyone had a similar problem and if so, what could the fix be.
Thanks, John.

blown cv even with the hubs out this may affect it

Hello,
Would a blown cv afect the steering if the hilux is sitting still aswell, and if so, could it bind up in any position (left, right and straight as that is what this is doing)
Thanks, John.

yes . have even herd of people blowing them and driving home then get half way and it binds up a 100 in 2wd and the hubs out.
if the broken pieces move the wrong way it will jam