Gears 2014 GMC 6.2L 6SP 6" Lift 35" Tires - 4.10 or 4.56??

shuckeba · April 28, 2015

I have a few questions about what size gears I should get for my truck. Currently I have 6.2L 6SP, factory 3.42. I just got a 6" lift, 20" wheels, 35" Toyo Open Country tires, magnaflow catback exhaust, S&B cool air intake, & an edge evolution programmer. Of course before I got the lift and tires, my truck was a beast. Loved the new found power and torque. Now since the lift & tires, it still has power, I can feel it dragging much more and MPG went to crap. I was expecting some MPG degradation but I lost much more than I anticipated, about 7 MPG. Although I'm good with it, its a truck and you don't buy it for MPG, its the drag I don't care for too much.

I drive about 18K miles a year, much on the highway 70MPH+. I also tow a boat on many weekends, a 8000lb camper on weekends, & sometime both at the same time b/c you can't go camping at the lake without a boat.

I have did some research and finding mix reviews. The max towing package, which I don't have, for my truck comes with a 3.73. Looking at the charts, converters, and reading comments, I should go to a 4.10 or 4.56. I was leaning towards the 4.56 just for the pulling power but what I've read, I should get a 4.10 b/c of the 6SP. 4.10 will also get me better MPG but I will lose the torque. Since this project isn't cheap and I want it done right the first time, which gears would be best with my current setup? 4.10 or 4.56? I want the best bang for my money and to get it back to at least, if not better than factory.

Jon A · April 28, 2015

The question that probably needs to be answered first is what gears are available. I don't know of any 4.10 or 4.56 R&P sets for the 9.76" rear yet. 3.73's are, but I don't think they're worth the hassle. I'm waiting for somebody to make 4.10's.

LifeisthePits · April 28, 2015

They have gears up to 5.13 now, Yukon makes them for sure I talked to them a while back. I am running 3.42's with 37's right now. It has a good tune on it and it still gets up and goes like a champ.

I was going to go to 4.88 as I have done in the past with 37's but that seems like aggressive overkill with this powertrain. After looking at it I think I am just going to go with the factory 4.10's and to be honest if I had 3.73's I wouldn't even bother upgrading.

I wouldn't go above 4.10's with this powertrain for 35's and if it were me I would just do the custom tune and call it a day.

shuckeba · April 28, 2015

Don't get me wrong, my truck has a lot of power. I just want to be able to pull my camper like I did before I got the the tires and lift and have the little bit of luxury of a big engine with decent MPG, something I lost with the tires and lift. Although I am leaning to a 4.56, my gut tells me to stay at the 4.10.

LifeisthePits · April 28, 2015

Don't get me wrong, my truck has a lot of power. I just want to be able to pull my camper like I did before I got the the tires and lift and have the little bit of luxury of a big engine with decent MPG, something I lost with the tires and lift. Although I am leaning to a 4.56, my gut tells me to stay at the 4.10.

I am right there with you, my natural instinct is 37's with 4.88's but overgearing is just as bad as undergearing, especially for highway driving. For you 4.56 would be about the same as me going the 4.88 route. With labor so pricey on install you want to do it right the first time. With 4.10's and a good tune you will be on the power side and have more than enough to pull a camper. Only reason I would go to 4.56 is if you were planning on doing a good amount of offroading where you will need it.

Jon A · April 29, 2015

They have gears up to 5.13 now, Yukon makes them for sure I talked to them a while back.

That's good news. I wasn't able to fine anything on their website, I guess it might not be updated yet.

Stoddard · April 30, 2015

That's good news. I wasn't able to fine anything on their website, I guess it might not be updated yet.

Yeah, they show 9.5" online but no 9.76". I know the carrier and axles are the same but the housing is different so you couldn't just throw in the 9.5".