GM and Gearing

They are around 10% apart...meaning about 10% torque multiplication difference...more if going up numerically and ditto going down numerically

Factored by the transmission gearing & number of gears...this includes tire revs per mile being the same

Of course gasoline vs diesel factors

What will you will tow, how much will you use the truck without a load and where will you be going with a load?

It sure I’ve seen that tall of gears in a GM HD gasser since the 80s models.
They’ve only offered 4.10s for several years now.
Regardless of all that, if you’re towing anything substantial get the deepest gears you can. Mileage will s uck just the same.
If you’re only hauling heavy loads like firewood and don’t really tow , then the pavement princess gears will be fine. Idk where you’ll find them though in anything built in the last 20+ years or more.

Be less vague with your question.

Which transmission? I don't think you would want the 3.42 if it's a 6 speed.
Mark

What year 2500? Earlier model 3.73 was standard, and then about 14 4.10 was standard. IDK if 3.42 was an option?

Jerry

jffnkrn, come in....you gotta copy?
What mystical model do you have?

NVM, figured it out. 3.42s were offered in K20s or K2500s between 1984-1987, with the 350 or the mighty 6.2 diesel.


What do I win?

Grit,
You win nothing!

For the rest of you, I guess grit too! Not sure why......

For 2021 the two GR options are 3.42 or 3.73 behind the 6.6 gasser. I don't recall looking this up las week if that motor has the 6 or 8 sp auto behind it.
If the 6sp, I'd be ok with the 3.73. would have to do some number crunching on the 3.42.
Need to look up gear ratios on 8sp to see if first is lower than the 4.10 1st gear in the 6sp. Is so, then a 3.42 could work on all ends, possibly get you some decent mpg's on freeway empty at 60-65 mph.
I do a lot of 0-50, a bit at 60. Almost none at 70!. So 3.73 generally speaking is best for me. Would prefer 4.10s even with the 6sp.

Marty

Now that I look it up. the 3.73 is gas only, 3.42 is a diesel option, At least pricing a building a gas version. Gas has the 6 sp auto, diesel the 10 sp.

marty

You can get the 3.42 connected to the 6.6 gas - just need to buy the Express van.