The 4500's, 5600's and g56 all have issues to one extent. Standard has remedies for them all and has the updates done on the units they sell. I believe any of them are an improvement over what you have. Depends on how much you want to spend. Of the 6spds, the 5600 is the best with their gear fix. Check out the website. My truck is a 04.5 h/o with the nv5600 in it. Great unit. Run Amsoil in it with the 1-2 qt overfill done through the shift tower.