Who has 4.56 Gears in there 8 speed transmission?

[NEMESIS-A/T]

Im scheduled to have my gears installed in 2 weeks by East Coast Gear Supply, and I have decided to go with 4.56 gears. I have a 2016 GMC 4x4 with a 10" lift and running 38" tires. I currently have 3.42 gears and it does "OK" as long as I keep it in tow haul mode.

I was hoping someone who has the 8 speed transmission and 4.56 gears could chime in and give me some feed back. I also considered 4.10 gears, but I think 4.56 is the way to go for my set up.

[Nosaves]

What a monster of a truck lol awesome. 

[NEMESIS-A/T]

Im really hoping someone has some RPM data to share. Id like to know what there real world feel is for 4.10 and the 8 speed transmission.

[Jacoby]

You won’t find anybody with that setup in here. A few folks have talked about wanting to regear with 8 speeds but then they disappear and nobody hears from them again

 

im sure there is a calculator out there you can plug in all the numbers and get pretty close rpm to mph

 

i have a 7” lift on 35’s with 6 speed and 4.56’s and my rpm at 75mph is 2200.

 

I figure with 2 more trans gears and a lower rear gear ratio your rpm will be lower than that. Maybe even a lot lower. With those big ass tires of yours I figure your 3.42’s are essentially acting like a 2.93 give or take. A 4.10 might get you back to a 3.42 ratio but not exactly sure. From what I’ve read with the 8 speed you don’t have to go as big in the rear like you do with a 6 speed but what I read was not from folks with gears and 8 speeds but from guys just doing the math. 

[NEMESIS-A/T]

Your right, I noticed a few good threads that went no where. No fallow up or review. My final drive is .65 and I have punched in the numbers. It says with 4.10s I will be at 1,700 rpm doing 70 mph. 4.56 gears put me at 1,800 rpm at 70 mph. I like the 70 mph mark for gauging the highway drive ability. Might be wrong. Im unsure at the moment and hope to get more good feedback. Thanks for your input.

[Slizzo]

Let us know how this ends up.  Do you have ability to tune for the new rear gear?

[Jacoby]

3 hours ago, NEMESIS-A/T said:

Your right, I noticed a few good threads that went no where. No fallow up or review. My final drive is .65 and I have punched in the numbers. It says with 4.10s I will be at 1,700 rpm doing 70 mph. 4.56 gears put me at 1,800 rpm at 70 mph. I like the 70 mph mark for gauging the highway drive ability. Might be wrong. Im unsure at the moment and hope to get more good feedback. Thanks for your input.

Yeah at 70 I think im right at 2000 rpm.  Around here if you're going 70 then you're going to slow lol. 

[imiller1974]

What's your plans for gear break-in, since you're in SC? I'm in Lancaster, SC, East Coast is in Raleigh, about 162 miles, one way.

[3tspapat]

IMO, I think it will feel boggy with 4.10's. At minimum i would go 4.56s. 

[NEMESIS-A/T]

2 hours ago, Slizzo said:

Let us know how this ends up.  Do you have ability to tune for the new rear gear?

I will not do what most have done with there gear threads. After I have gotten a feel for the temperament of the gears, I will post MPH and RPM comparisons. 

[NEMESIS-A/T]

11 minutes ago, 3tspapat said:

IMO, I think it will feel boggy with 4.10's. At minimum i would go 4.56s. 

Your right.. I changed my order with them this morning for 4.56 gears. 

[NEMESIS-A/T]

41 minutes ago, imiller1974 said:

What's your plans for gear break-in, since you're in SC? I'm in Lancaster, SC, East Coast is in Raleigh, about 162 miles, one way.

Not sure what you mean. East Coast Gear told me I would be good to go. I do plan to stay the night in Raleigh so I will be driving around and letting the gears get heat cycles.

[pewterliftedz]

IMO 4.56s are a better idea for that big of a tire, and since you have 3.42s already, I'm going to assume you have a 5.3.  A 4.10 ratio would put you equivalent to stock tire height, but will not account for the extra rotational mass you're carrying now.  Is your truck tuned, or do you have a programmer to recalibrate your speedometer?  Also your 8th gear ratio is 0.67 and a 6L80e 6th gear ratio is 0.65, so your cruising highway RPMS would be the same with either trans.

[3tspapat]

I think he has the 6.2. 

 

8 speed 5.3 only with the tow package or eAssist no? 

 

 

[pewterliftedz]

1 hour ago, 3tspapat said:

I think he has the 6.2. 

 

8 speed 5.3 only with the tow package or eAssist no? 

 

 

The only way to get the 6.2 with 3.42s is with the Max Tow, which isn't compatible with the All Terrain package.