I have a 2003 2500HD 6.0 and a what is supposed to be a 4.10 rear end. Ive always understood that they didnt even offer the 3.73 rear end in the 03+ HD models. Cruising at about 60 im turning about 2300 RPMs which isnt too bad. Im just wondering if i really have 4.10s or not because if i hammer it from a stop, i can go about 40 in first gear, 78 in second gear, and close to a 100 in third. Just doesnt seem right to me that a truck with 4.10s will go 78 MPH in 2nd gear. I dont know anyone with the same truck as me so i dont have anything to compare mine to. Just wondering how my truck is compared to you other guys'

Newbie here. Just bought my first truck (ever). That motor sounds soooo good! Anyway, I have 3.73 gears and at 2000 rpm, I am doing about 71 mph. hth

I have a 2003 2500HD 6.0 and a what is supposed to be a 4.10 rear end. Ive always understood that they didnt even offer the 3.73 rear end in the 03+ HD models. Cruising at about 60 im turning about 2300 RPMs which isnt too bad. Im just wondering if i really have 4.10s or not because if i hammer it from a stop, i can go about 40 in first gear, 78 in second gear, and close to a 100 in third. Just doesnt seem right to me that a truck with 4.10s will go 78 MPH in 2nd gear. I dont know anyone with the same truck as me so i dont have anything to compare mine to. Just wondering how my truck is compared to you other guys'

1) Open your glovebox
2) If you're like me, take all of the crap out of the glovebox so you can see the RPO tag
3) Look through the codes..They are in alpha-numeric order GT4 = 3.73 gearing
GT5 = 4.10 gearing..

Hope this helps..

I have a 2003 2500HD 6.0 and a what is supposed to be a 4.10 rear end. Ive always understood that they didnt even offer the 3.73 rear end in the 03+ HD models. Cruising at about 60 im turning about 2300 RPMs which isnt too bad. Im just wondering if i really have 4.10s or not because if i hammer it from a stop, i can go about 40 in first gear, 78 in second gear, and close to a 100 in third. Just doesnt seem right to me that a truck with 4.10s will go 78 MPH in 2nd gear. I dont know anyone with the same truck as me so i dont have anything to compare mine to. Just wondering how my truck is compared to you other guys'

I have 4.10's and I'm turning about 2400 RPM at 65-70 MPH on stock 245's. It definately sounds like you have 4.10's

GT5 code in glove box = 4.10