I have a 1982 pickup 4x4, 22r with a weber and 3.91 gears front and rear. Right now I'm running 235/75R15 and would like to go to 31/10.50R15. Has anyone run the 31's with the 3.91 gears. If so how did it work out and how was the gas millage if you know. If anyone has a good lead on a decently priced set of 4.10 of 4.11 I would also be interested. Truck is being used for a DD so decent gas millage is needed, or as good as these trucks can get. But I also would like to use the truck for mild off-roading, that's where the 31x10.50R15 come in. In all reality I would like to get some 235/85R16 but don't want to get rid of my original chrome SR5 rally rims.

 

I ran 31s and 3.91s in my 81 and it was ok but when I went to 4.56 and 31s its was great for city but on the high way they were a little tall

My dad ran 4.11s and 31s in his 82 and he liked how it worked and got better gass mileage overall then I did with ether set up he has since gone to 32s and 4.56s

so I have a pair of 4.11 3rds out of my dads 82 I am selling PM me if interested asking $200 for the pair plus shipping (one is spooled the other is open. I still have to original open carrier and can swap it back out if interested)

 

Personally I don't think the cost and time swapping from 3.90's to 4.10's would make it worth it

Are you positive your 82 has 3.90's? Always thought they were only in 82 unless someone swapped gears

So some math with this gear calculator

 

http://www.grimmjeeper.com/gears.html