Dump bed removal

I have done it several times with dump trucks and a dump trailer.
I used a backhoe bucket against the barrel of the hydraulic cylinder on the side the cylinder is leaning towards, when the body is in the raised position the cylinder will most likely be leaning towards the back.
I also tied it off in both directions with 2 ratchet straps.
Then used the backhoe to remove the cylinder
The body needs to go high enough for the cylinder to retract past the underbody of the dump bed.
If the body has a raised position stop do not use it to keep the body up until the cylinder is removed, block it across the frame with either a steel beam or hard wood blocking chained to the frame in case it slips.
You are going to have to lower the body and remove it with something that has enough lifting power, i welded 4 chain hooks on the upper inside of the body and used a 75K lb excavator.
Just did this last year to a dump trailer that snapped the kingpin that was directly under the cylinder.
Note: if it is a inverted cylinder "older Brandon-Beauroc Canadian Body" etc you can take the top retaining nut off before you raise the body up but you should secure the female cylinder retainer so it doesn't tip out towards the cab when lowering the body.
On a dog house set up you will need to remove the retaining pin at the top of the cylinder with the body raised while being secured with the steel beam or hardwood blocking.

 

I usually pick them up with a loader, or two, depending on what style the bed is and how much I care about it.

I've used 2 loaders with one on each side, that time was to pull the truck in the shop and change wheelbase, put the truck where I wanted the body in my yard, one loader on each side, drive out and put some cribbing on it and set it down. it had a good heavy bottom outside rail on a square body.

Pulled an elliptical off that I knew I would never use again, but wanted to not damage it too bad for resale, got a loader bucket on the back end and ran a chain up to the doghouse and pulled it off that way.

I've likely got to pull one off in a couple weeks for some major maintenance. I'm feeling a little lazy, and have a friend who runs a crane, so I'll probably just have him set it off and back on for me.