I'm about to get a new Duramax 2500 Z71 LTZ. This will be my 3rd. I see that most of them are either 3.73 or 4.10 Ratios. I'm not sure what mine is, and the door edge sticker codes aren't clear. I'd like to get the same that I presently have. I typically am pulling my boat, but occasionally a 38' travel trailer, and a 20' trailer with a 75 hp Deere tractor. Will be pulling the travel trailer more as time goes on, but still most of the time just my brief case. I'd like to figure out what mine is. Can anybody tell what code indicates the gear ratio? I'm leaning towards a 3.73 for the better mileage. Thanks for your help.

http://www.crawlpedia.com/rpo_axle_codes.htm


To find the axle gear ratio of any GM vehicle, locate the RPO sticker (typically located in the glove box) and write down any codes starting with F, G, or H. Then, find those codes in the table below.

I don't believe GM has ever made a duramax with anything other than 3.73 gears. 4.10's are an option but when you select the duramax engine that option goes away and you get 3.73's as the only available offering.

Thanks for the link Samson. Looked it up, and mine is a 3.73 Red, 3 of the 8 2500 Duramax's at my local dealer are 4.10's. Might be an 18' thing. I'm going to stick with a 3.73. Unless you pulled a backhoe I can't imagine needing 4.10's. That 75 hp. Deere, or a 70 hp track skid steer are easy enough for mine with 3.73's.

Are you looking online? I bet its an error or typo.

Just looked on their website, with the duramax comes 3.73 gears only way it comes.

There's 3 18's at PArkway with 410's on the spec sheets. Maybe they special ordered them. I'm going 3.73's anyway

I just bought a Duramax it has the 373 gears would not get anything else. Had a 97 with 373 then a 2009 with a 342. The 373 ran circles around the 342 in all as specs.

GM doesn�t and has never produced the duramax with anything but 3.73�s. The duramax is an option. 4.1:1 gears will be listed as standard equipment and along with the duramax under optional will be 3.73�s.

Wish one of the gm dealers would respond lol none of them have 4.10�s

As far as I know, when you add the duramax option it switches from 4.10s to 3.73. Only the gas engine comes in 4.10s.

All you need is 3.73 in any diesel. I had 4.10 in a Power Stroke and mileage sucked my 3.73 Duramax's way out towed and worked the 4.10 Power Stroke plus Top Speed was 82mph and it was rmp'd out.

Transmissions are little better nowadays with more gears and higher o/d gears. Low axle ratios don't bother me.

The �18 duramax is one bad motha, and it can pull wayyyy over 82 mph....

Duramax only used 3.73 as far I as know. Best diesel put in a pickup. Paired up with that Allison transmission, bad son of a gun

I�ve got a 2018 with the 6.6 duramax, I will NEVER own another gas burner as my main truck, maybe for a 3rd vehicle.

x2. I've driven/towed with gassers mostly. Got the Duramax, never again a gasser. Those new L5P's are power houses!

The night and day difference between towing with a gasser and a diesel even with my light of a boat (~4,000) is completely incredible. RV weighs around 6500lbs and I will say, my favorite part about going camping now is hauling that trailer through the hills of East Texas and the hill country. Best part is going up a grade with the cruise on 70, that Allison sticks in 6th gear and you hear that Duramax grunt and groan and chug on along over the hill. Gasser would drop 2 gears and hit 3500RPM.....

D-max ain�t grunting with 6500 lb travel trailer!

By grunting I don't mean struggling lol. I guess another way of saying that is "mean sounding"

You're mostly correct but because of so many option levels, mid year changes, and customer custom ordered espcially on work trucks we don't go by the thinking that this is the only way they come. It's best to know what they have by looking up the vehicle build on our special GM website. When we order parts for vehicles we don't tell the parts guy what gear ratio we need or what color a part is. We tell them what we need like a "ring and pinion" or a "door panel" and give them the last 8 of the VIN. They then look up the parts by that vehicles build sheet and give us the part it was built with.

If you want to know what your vehicle was really built with call your local GM dealer parts department and ask them. They will need the last 8 numbers of your VIN to look it up.

redchevy is correct. Every 2500 or 3500 with a duramax (since 2001) will have 3.73's. In this unique case it is very cut and dry. There were no mid year changes, no custom ordering for a different ratio, nothing other than the buyer changing them after purchase.

The only exception in regards to the Duramax would be the Kodiac (top kick?) medium duty trucks. I believe they were available with 4.56 or were all 4.56 not sure.

I pulled up the 8 that where at the dealer the OP said... 3 of them list 4.10 gears and a 6.0 L gas v-8.

You can even get on Chevy's "Build And Price." As soon as you add the Duramax in the truck, it takes away your 4.10's and adds 3.73's.

Wonder why GM doesn't allow 4.10's on the Duramax..?

Because you don't need extra torque. It would just be a useless gas mileage hit.

3.73 = 6.6L Duramax Diesel
4.10 = 6.0L Gas

Nice to hear so much positivity on the duramax. Never owned one but always wanted one. i have the 5.3 and was thinking about upgrading to the duramax but constantly hear ppl dogging it. too many powerstroke guys with too many opinions i guess!

Honestly think you would be hard pressed to go wrong with any of them these days, they are all solid trucks. Ours have always been good. Most people are just brand groupies and don't know much about anything.