Winch motor or battery problem?

I used my winch to pick up the front of a parts rig to move it to another location in the yard. When I triggered the winch to pick up the the other jeep the winch seemed really weak. I was just picking up the front of the jeep which has everything but the guts of the front axle( this is why I was moving it this way),motor, tranny,t-case, etc.still in parts rig. I picked it up to where I could move it but when I was finished I went to roll up the exccess winch rope and the winch seemed like it was being bound by something,
It would roll around and slow down then speed up again then slow down again and speed up again, etc.I was wondering if anyone has experienced this too and know weather its the winch or the battery.I do know when you get winch cable all piled up on one side the winch it kind of binds up but this is not the situation here, the winch rope is rolled up neatly with plenty of space.
Any thoughts or suggestions?
Thanks

Mark, I'd look at all the connections... (Trail rig yes?) maybe replace the batt if it tests bad? but I'd check & clean all the connections first, and replace any suspect cables.