Yazoo YR60 counterweights/traction problems

I am having traction problems with my YR60 on small hills. Seems whenever I hit any hilly terrain in the yard, the tires break loose and the only way I can get them to grab is to either stand up, or throw it in reverse until the ground levels out.

I have seen several of these mowers on Ebay recently and some have a large boxy looking thing hanging off the frame in the very back of the mower. Are these weights, and do they act as a counterbalance for the heavy deck? Are they used to get more traction on hilly ground? Anybody have an idea of how much weight I'll need back there?

Thanks in advance,

Kurt

Thanks for the reply. I don't think the terrain here is too hilly. Last night I was looking through the exploded diagrams looking for one of the arms for adjusting the belts on the deck, and saw a part number for a 90 lb weight that attaches to the tailframe under the seat. Only guess I have is the outfront mower decks of the 60's and 76's changed the weight balance of the mower too far forward and the weight was needed to allow better traction at the wheels. I'm not sure of this, but the mower I have (60") does very well on flats and very slight inclines, without the weightset in back. Starts to slip when ground is damp on the inclines, and on steeper hills when it's dry. Standing up does help. I'm just trying to work through this traction problem, aside from a terminal case of belt adjustments, the mower does a great job.

Kurt