[sweetk30]

i tow with a GMT-400 1.5 ton 3500-hd truck . its a 8.1 bbc vortec and nv4500 combo with 4.63 rear gears . the trailer i pull every day is 10k loaded full .

i would not go lower if you have any hills . if its all flat land and no hills to climb maybe go better gearing . but its a work truck let it eat and just work .

my truck was ether 4.63 or 5.13 gear . i live in a lot of hills and long climbs and wish i had the 5.13 for that stuff but the 4.63 does good so i just run it .

make sure tire height is correct and bigger = lower rpm but more work for pulling loads . and changing gears = lots of money and unless BIG change its only a few 100 rpm change per jump .

if what you have is working but want more i say go bolt on over drive to let you split each gear to make it a 6 speed . but yes lockup conv on a 4L80-e is nice . but if pulling BIG / HEAVY loads do NOT pull in O/D as it will kill the clutch pack and clutch in the conv faster . years ago i had a truck with a vac guage and it got better running performance in 3rd than overdrive when pulling a loaded trailer . it was a vortec 350/4L80-e / 4.10 combo .

good luck and plan correctly as most changes take for ever to pay you back unless you use it that way every day .