The 770 is a great little tractor. It replaced the 750, which was bulletproof. I had a 750 and never had a problem with it. I now own a 4300, and although it's a great tractor, I think the 650-1050 series tractors were superior (simple design, fewer problems).
I think the 770 was the predecessor to the 790, maybe just a few less hp. I have a 790 and love it. Depending on your needs it should be a fine tractor for you /w3tcompact/icons/smile.gif
1988 John Deere 750, 1938 McCormick-Deering (Farmall) F14
Jump on it. I've got a 750, which as stated below, is bulletproof. I'd move up to a 770 in a heartbeat for the power steering and the full synchro transmission.
I have had one for the last 4 years, i pull a 50" tiller and a 6' backblade without a problem. The tractor has never missed a beat, my only want would be 4wd (which yours has /w3tcompact/icons/smile.gif). I would definitly recommend any of the "70" series tractors (670,770,870,970,1070), I'm told the "55" series hydros' are just as good.