I currently haul a 34' horse trailer, 6500lbs unloaded and 14,000 loaded, with a Ford 350 V10 dually. Almost from the beginning of using this truck to haul I experienced problems with the slip differential on the rear axle. The axle has been replaced a number of times, the "special" oil has been used, and every and all other possible fixes have been done to this truck to no avail. What I get is a serious thunking through the rear end on turns - tight and not-so tight.

I've given up trying to fix this one and am about to purchase a new truck -- possibly the GM diesel. I see there are is an option called a lock differential - is that what I need? Or will I always have this rear end problem after hauling a heavy load?

My second question is "do I need a dually? or can I get away with a simple four wheel truck? I always assumed the added back wheels were for insurance against rear tire blowouts.

Thank you,

Rollopg

Hi, when you changed the diff oil, did you use the additive for limited slip differentials? Limited slip differentials have a clutch that joins both axles and needs an additive to make the clutch work properly. With late model GMs, there is a locking differential option that is more of a mechanical solid joining of left and right axles.

In this forum under "Trailers 101" in the post, Duallie vs single wheels, I give my opinion on duals. With the weight of trailer you tow, I would get duals.