I'm about to swap from 3:42 to 3:73 gears. Does anyone have personal experience with this? Or anyone knowledgable enough to guess how this will effect my gas mileage? I do 75/25 highway/city driving. Mods and tire size in sig.

 

I did the same swap and lost 1mpg, and picked up 2-3mpg pulling a load..

 

Not worth the swap. go 4.10's . If its tuned right in town milage will be better.

 

Hotrod, was that with the 6.0? And how much highway driving do you do?

Slowec, 4:10s would be to much for me 75% of my driving is highway with no load.

 

3.90's ?? You are running a 31'' tire..

 

I already have the 3:73s. I don't race or anything like that. I'm doing a posi swap and just wanted something a little more peppy than the 3:42s.

 

Oh well then slap them puppies in.. Your not going to notice it much..

 

I had the 4.8 @ the time.. Only did the swap to help out with towing.. I was making 300plus trips to work & back.. Went from 20mpg to 19mpg empty
10mpg to 12mpg loaded..

 

Thanks for the info hotrod.

I was planing on doing a underdrive pulley next. So maybe I can pick up the 1-2 mpg loss from the gear swap.

 

Engine won't be under as much load with numerically higher gears. This alone will help to increase MPG.

3.42 to 3.73 won't be very noticeable, but an improvement nonetheless.