This problem was actually pretty common with my Woods BB60 (and all of the other Woods brush hogs I've seen). You've got nothing more serious wrong than a lack of grease on the shaft that the rear wheel pivots around. That cured my problem. If you look at the manual, I think it says to grease that shaft every 8 or 10 hours of operation (going from memory here). There is no bearing in that joint, just a shaft through a sleeve. It doesn't take much to lock it up. Grease also tends to work out of it pretty easily (or wash out if you left it out in the rain). If you get tired of greasing it that often, find a good waterproof grease and it will last a bit longer.
I would definitely try greasing it up before you try anything more drastic.
BTW... your toplink should not be carrying any weight when you are mowing, except in unusual circumstances. The Woods brush hogs have a short swinging link that the toplink attaches to. You leave a little slack in this, so the deck rides on the rear wheel. The slack lets the deck ride up and down a bit and follow the contours of the ground.
John Mc