Mud Hog is a brand of RWD axle for combines. They are one of 2 manufacturers that I know of. The Tuthill Corporation purchased Mud Hog's name and company in 1999, combining the manufacturing of Mud Hog hydraulic axles with its current line of integrated suspension systems. When Mud Hogs popularity expanded, Tuthill made the brand a separate line of business, calling it Tuthill Drive Systems. They are located in Brookston, IN. They are great bunch of people. We had a wheel motor on the Mud Hog on our 8010 blow a seal this fall, and they rebuilt it for us. Got us going in about 6 hours. Mud Hog designed the factory RWD axle for John Deere then at the last minute John Deere refused to sign the papers for them to produce the axle. John Deere instead took the design to another company to manufacturer the axle. So Mud Hog does have a axle for your 9660. In fact John Deere is the only OEM manufacturer that Mud Hog doesn't make the axle for original equipment. As far as cost call (219) 279-2801, and ask for RJ. I can tell you it's cheaper to go direct. A new wheel motor for our 8010 was $14,000 form CaseIH and $12,000 direct from Mud Hog. We opted for them to rebuild ours for $4,500.