[AT] JD 4020 lift problems

[John Hall]

When we try to lift something really heavy with the 3pt hitch with dad's 
4020, it has become a struggle lately. You have to rev up the engine a bit 
and then it will start letting it back down instead of holding it. I don't 
suspect the pump since we have no trouble lifting equipment with cylinders 
on it. We really notice it when we have the boom on it. So you can 
understand, this boom is made out of the tongue of a log cart, to put it in 
size perspective. We always knew when we were lifting too much as the 
tractor would lift it's front end off the ground.

Anyway, does this sound like a valve with an issue or possibly bad rings on 
the lift cylinder? Maybe something with the load and depth control?

John Hall