gear changes for better towing

I feel your pain....I had an 05 GMC hd 2500 2wd that I bought used. The prior owner put on Hummer wheels and huge tires....looked cool but towing was awful. I first changed to a set of stock size tires and wheels and I was going to change the gears from 3.73 to 4.10, but just swapping the wheels and tires made a huge difference.

I was amazed at the difference and did not bother with the gear change...my daily mpg improved a bunch also....I have learned that the factory engineers are smarter then I am when it comes to designing a vehicle....haha