My 2005 GMC Sierra 1500 has the 5.3L (300hp) with 3.23 gears. I'm towing an 18' TT with a stated dry weight of 3215 pounds and I realize that this number is only a starting point for what I will be towing. I haven't towed it for any long distances since I just purchased it 3 days ago. It was about a 60 mile drive on relatively flat highway against a 16 mph head wind and it was a miserable experience. Transmission was constantly hunting gears and gas mileage cut in half. I'm not as concerned about the gas mileage as I am about pushing my truck too hard.My question is has anyone replaced their running gears. I'm interested in ballpark figure on costs, effectiveness and feasibility. I'm pulling it back to Corpus Christi, Texas from Kansas City, Missouri and eventually will be living in it in Terlingua, Texas (close to Big Bend National Park) with an elevation of about 3500 feet so there will be some long grades.Thanks!

Does your truck have a tow/haul mode? If so use it.

I have a 2006 Ford F350. I use an SCT tuner. Simply plug into the trucks computer port below the steering wheel and change your tranny to what ever gear ratio you need at the time. Anything from gas economy to sheer power. Best $400.00 I spent in a while. Even tho you drive a Chevy...I thought maybe this could be of some help! :B

It should have the tow/haul mode. Engage it when towing and it will increase the shift points to keep the engine in its powerband. Not sure if the 05 has the 6speed trans. I thinks it's a 4speed. If it's a 4speed then 3.73's will really wake it up and make it tow exceptionally well.

I use the tow/haul mode but it only changes shift points and does nothing for the torque band. The 2005 has the 4 speed auto. I even considered a swap for the newer 6 speed but it's quite an ordeal since the newer tranny is longer.

dodge guy wrote:If it's a 4speed then 3.73's will really wake it up and make it tow exceptionally well.I talked with a guy that did my brakes a few weeks back and he suggest the 3.42 saying it would perform as well as the 3.73 would with my tire size of 17". Not sure if he knew what he was talking about or not.

Changing running gears | Good Sam Community

corvettekent
Explorer
Apr 16, 2017
Does your truck have a tow/haul mode? If so use it.
cruiseruser
Explorer
Apr 16, 2017
I have a 2006 Ford F350. I use an SCT tuner. Simply plug into the trucks computer port below the steering wheel and change your tranny to what ever gear ratio you need at the time. Anything from gas economy to sheer power. Best $400.00 I spent in a while.

Even tho you drive a Chevy...I thought maybe this could be of some help! :B
dodge_guy
Explorer II
Apr 16, 2017
It should have the tow/haul mode. Engage it when towing and it will increase the shift points to keep the engine in its powerband. Not sure if the 05 has the 6speed trans. I thinks it's a 4speed. If it's a 4speed then 3.73's will really wake it up and make it tow exceptionally well.
roadjunkie
Explorer
Apr 16, 2017
I use the tow/haul mode but it only changes shift points and does nothing for the torque band. The 2005 has the 4 speed auto. I even considered a swap for the newer 6 speed but it's quite an ordeal since the newer tranny is longer.
roadjunkie
Explorer
Apr 16, 2017
dodge guy wrote:
If it's a 4speed then 3.73's will really wake it up and make it tow exceptionally well.

I talked with a guy that did my brakes a few weeks back and he suggest the 3.42 saying it would perform as well as the 3.73 would with my tire size of 17". Not sure if he knew what he was talking about or not.
roadjunkie
Explorer
Apr 16, 2017
I'm also reading that gear changes can be expensive and problems can occur down the road. I suppose the best way around that would be to swap rear ends from a wrecked vehicle but I'm also reading about tuners. Can a tuner significantly improve my towing?

My 5.3L is rated at 295hp. I've added a catback system with Dyna-Flow mufflers and a CAI that would push it a hair over 300hp. What I lack is the torque. Can a proper tune add torque or the benefits of more torque?

In a perfect world, I'd be able to afford to buy a big diesel but that's not an option for me. I've put a ton of money and parts in this truck because I plan on keeping it until I die so I don't want to abuse it.
ScottG
Nomad
Apr 16, 2017
Gas tuners dont add power a lot of torque. You may get around 10% and that will be up high in the rev band. It will require premium fuel.
I really dont think a tuner and gearing will do what you wan't it to do. To get the performance you desire, you need to increase torque by about 40% or more.
You have run into the experience that so many of us have; not enough tow vehicle. The good news is you will never let it happen again.
I honestly think you'd be much happier with the results if you traded it in on something else.

JMHO, best of luck to you,
Scott
Busdriver
Explorer II
Apr 16, 2017
Do you have a tranny cooler, if not you need one, if you do a gear change go to 4:10 will not hurt your fuel mileage muck over 3:73, the 2500 chevys with a 6.0 come with a 4:10
roadjunkie
Explorer
Apr 16, 2017
Busdriver wrote:
Do you have a tranny cooler, if not you need one, if you do a gear change go to 4:10 will not hurt your fuel mileage muck over 3:73, the 2500 chevys with a 6.0 come with a 4:10

I'm sure it has a factory cooler but I'll be adding something better. I've even considered replacing the 4L60E tranny I have now with the 4L80E that comes in the HD 4WD models. I can buy a new one for less than $2k and a lot cheaper than a rebuild. I spent $2500 on a rebuild job on a Jeep Grand Cherokee.

I had a 3/4 ton GMC Sierra 2500HD 4WD and 4.10 gears that I traded for my current truck because of poor gas mileage and I didn't think I'd ever be towing anything larger than a utility trailer to take my zero turn mower in for service.
time2roll
Nomad
Apr 16, 2017
Go 4.10 and don't look back. You should be cruising down the highway at about 2700 rpm.