I own a 02 Chevy D/A 3500 4X4 and pull a 6 horse trailer with it. The truck has alot of power but it does not like to stay in 5th gear when it hits a small hill on the highway. I run around 70-75 mph to try and coast up the hills but sometimes the hill is too long and it has to shift to 4th to maintain 70 mph.I feel that 4:10 gears would be able to stay in overdrive like my powerstroke i traded in had.What would I need to do to adjust my speed gauge and would the allison shift correctly or would that need changed too. Also i want to install a exaust brake. What needs to be changed on the allison to run ok with that. And one last thing, can the dealer scan my truck for these adjustments or will it just void my warranty.