I towed a 10K GVW 5th wheel for ten years in the west coast mountains with a 2001 auto with no exhaust brake including a trip from the west coast to Newfoundland back. As long as you are careful about speed control on hills, it isn't an issue. The 48RE's should be better as I believe the torque converter locks in second gear which it didn't with the 47RE. That said an EB would have been very nice and I love the one on my present truck. Some early 48RE's had an issue with thrust washer wear when using an EB. You might want to check that out.