Thank you all for your responses as they have been very interesting with a lot to think about and hope to seemore results. I can see the points on both sides. Another part of this equation is whether one should go with the 3:73 or 4:30 rear axle and will mmog be affected much with the 4:30. We only get 7.5-8.75 mpg at max now and hope to get better with a new truck. We do occasionally pull a large horse trailer to Colorado and hay and equipment trailers but maybe not enough to have to have the diesel. We only have a 3:55 axle which will has done the job but very slowly in the mountains of Colorado.