Gear ratio

cliobogger · June 18, 2013

How do I look up what gear ratio I have without taking the dif cover off and doing it that way? Is there a code in the vin or anything?

blackout07 · June 18, 2013

RPO code. I think there's a lookup on the forum homepage.

Chris · June 18, 2013

GU4-3.08

GU5-3.23

GU6-3.42

GT4-3.73

GT5-4.10

Carder09 · June 18, 2013

There are codes in the glove box I believe. At least in my truck there is.

cliobogger · June 19, 2013

Ok, I'm picking it up tomorrow, I'll check then. Thanks all for your responses.

cliobogger · June 20, 2013

I have the GT5 and G80 codes, I like.

pm26 · June 22, 2013

If you cannot find the code for some reason, you can jack up the truck by the rear differential until both rear wheels are off the ground and support the axle with jack stands. Then put the truck in neutral, climb under the truck and turn the drive shaft by hand until you see a complete 360 degree revolution of one wheel. The number of turns of the drive shaft it takes to spin a wheel one complete revolution is your gear ratio.

Edited June 22, 2013 by pm26

pm26 · June 22, 2013

Concerning the axle gear ratio on HD trucks, why is it that the optional 4.10 ratio is so rare on dealer's lots? Tow rating is drastically reduced with the standard 3.73 ratio and it seems odd that even most dually pickups with the gas engine are ordered with the 3.73 ratio. Gas mileage should not be of primary consideration when buying a heavy duty truck. And I believe that the 4.10 ratio will actually give you better mileage in city stop and go traffic. There will be some penalty at highway speeds, but nothing drastic. But anyway, I would definitely go for the 4.10 ratio because tow rating is about 3,000 lbs higher, which is significant. Also, with the 4.10 ration you get about 10% more torque at the rear wheels in all gears. This helps move heavy loads from a standing start.

therink · June 22, 2013

In order to get 4:10, I had to factory order my current and prior HD. It is very rare to find 4:10 on any dealer lot. I don't get it either. It is a $150 factory option. 4:10 is a must with the 6.0 for hauling anything over 10,000 lbs IMO.

cliobogger · June 23, 2013

Yeah, thanks pm26. I knew that method, I was looking how to get around doing all that, its about 110-115 every day here, so the less I have to do outside, the better. As well, I was very happy for the above reasons to find out I had the 4.10 gears.

gudde1251 · June 24, 2013

I am also curious about the WHY ? In the rural areas of the country, the 4.10 would be a great selling point. It must have something to do with GM meeting the government mandated MPG for their fleet....

davzog · June 25, 2013

I had the 4.10 on my last truck and thencurrent ride has the 3.73. My gaa mileage is about the same but it does not tow as well...my next rruck will most certainly have the 4.10, unless it is a diesel

sdeeter19555 · June 25, 2013

When I was looking, about 50% of the bare bones WTs had 4.10s...I will definitely hold out for, or order, 4.10s for the next truck.

2017HD · June 27, 2013

For 2014 your prayers are answered - the 4.10 gears will be standard on the 6.0L gas - the DMax will still have 3.73's

brainpause · June 27, 2013

I dare suggest that in areas such as Tennessee where we have rolling hills that 4.10's would probably yield better gas mileage. My 3.42 truck is constantly downshifting, even on interstate.