New transmission, and now a different problem???

Took my 2007 Freightliner 26,000 GVW Rollback to an Allison automatic distributor/service center and had a new transmission installed. My PTO works, but now just tried to load a heavier vehicle, and the winch pulls the car on, but there is not enough power to pull the bed back up onto the truck frame. seems to be slipping or bypassing somehow. Wasn't that way before. I once got a chain caught and didn't notice it soon enough and broke the cable with the 8000 lb winch. plenty of power - now wimpy? PTO has a clutch pack and air operated engagement. I was thinking pressure was bypassing from an incorrect over pressure setting.
I believe you screw in a 4000 lb. gauge on a tee to set this, but I don't have one over 2000 lbs.
I have an appointment to take it back Tuesday 8 AM. I'm afraid they will say they see nothing wrong.
They wouldn't put a new transmission in with my old torque converter, would they?
What could be wrong here?

 

Thanks!
I checked all that, and AOK, New hyd. filter, too.
Check the simple stuff first.
They took the PTO off totally, and had to remove hyd. lines from old tranny,
so I hope they removed the correct plugs on the new one to put those hoses back on?
Seems funny it works empty or light load, but not real heavy load.

I even greased the ways on the bed rails, Poor truck said "What's that stuff?"

 

Copy that, I have a 2000 lb. gauge, but don't know the range of pressure coming out of tranny.
Buddy of mine that is more hydraulic savvy than I am said you need a 4000 lb. gauge first to verify the range.
Don't know. I would think 2000 lb.range would be sufficient for a transmission?
If i knew where the relief setting was, I would just bump it up.
Keep watching the gauge and screw it in.
I believe its only a spring and plunger you would screw in to increase system pressure.

 

I agree, I have an appointment with service Tuesday 7 AM.
It's a warranty job now!!!
You engage the PTO switch and increase idle to 1200 RPM.
Transmission port puts out power to push 3 rods into the PTO clutch pack, to engage the main pump for that separate main hydraulic system.
You hear a rumble as pressure increases, but not enough to move the rollback bed forward 6' off the ground.
I think the small hose is transmission fluid that exits out the inside of the pump casting, draining back into the transmission body, after compressing the clutch pack.
I think there is a way to increase this pressure; hope they can do it with programming from a scanner, IDK?

 

Thanks Brian, for the reply.
I filled the hydraulic tank, it's full. (ask me how I know?)
I pulled the bed back up to cab, and the added volume
from the 6 foot cyl. overflowed the tank a little.
On billing the mechanic made a point to add "the backlash was checked and within spec."
I can see the hoses from the pump and no kinks are visible.

I notice that when engaged, it makes no sound, until I increase the idle.

That leaves torque converter, (I sure hope not,that means it has to come out again,)
relief or bypass valve stuck or broken - not probable; as it works marginally,
or low pressure from trans. to operate the wet clutches inside hyd. pump to engage,
that I hope can be turned up with their laptop or scanner.