I am about to get my tax money back and i'm looking at getting some lower gears and adding a eaton posi. Here is my question. I'm sure i don't want to go with a 4.10, and i know i would be happy with a 3.73, but do you think the 3.90 would be a good choice or would i even be able to tell the difference? I have a 3.42 right now and i know i want to go lower. Would the 3.90 have any noticable gain over the 3.73's?

 

The 3.90's would have a slight edge on the 3.73 down low. I would do 3.90 on mine.

 

Well how tall are the wheel and tires you have now?

 

When I was debating on a gear install, people kept saying "with 4.10s your gas milage is gunna suck" "your RPMS are gunna be way up there" .. etc..


all that info is FALSE. dont be discouraged with 4.10s too low of a gear. My city driving isnt really effected at all, and i cruise around like at 1200rpms-1600rpms around the city. at 75mph on the highway, its around 2500rpms.

But between those 2 choices, id go with 3.90s

 

Damn, I must be the only person that drives like 65-70mph on the freeway!

 

I went from 3.73s to 4.10s and only knocked about .15 second off of my quarter mile time, and made it that much harder to hook up, if you are gonna do further mods in the future, than the 4.10s might be too much. I am running 20" rims and tires, and have stuck with the same diameter wheels. I usually drive 80 mph on the freeway, and I do a lot of freeway driving. My gas mileage dropped about 2 to 3 mpg. When doing a lot of freeway driving, I used to get about 18mpg, and now, about 15.2 at the best. I do not notice any change in local city driving, and this is where the 4.10s come into action. If I would do it again, I would have left my 3.73s alone, especially since I am saving up for a Turbo on my truck! Now I run at 2600rpms at 80 on the freeway, and the truck feels like it is really running now at those rpms. I used to run at 2250 at 80 with the 3.73s. If I was to keep my truck stock for the most part, I would happily keep the 4.10s, but I am definately going back to 3.73s with the future upgrades.

 

When I changed from 3.42 to 3.90 I felt a difference when it would shift, but it didn't really show on the track. Maybe .05. I might have been over reving. But my truck was stock. Now i know they are working. I say go with it.

 

well i have the 4.10 gears and get 19.5 to 21 on the hwy going 80 mph and i went from 3.42 gears to the 4.10 and droped 1/2 second of my 1/4 mile times. Now traction can be a issue with stock tires but my 18x9 and kumho tires i can leave at 1200 rpms and no spin. hope this helps and if not go with the 3.90 lol later, kevin

 

Totally agree with Deckhand, i went from 3:42 to 4:10 and i really didnt notice any difference in gas milage and my highway rpms are fine right about 2000 at 70mph, but the down low acceleration was definitly better. The one thing you got to remember as far as the 3:90's go is the only way you are going to be able to calibrate your speedo is with a custom tune, as far as i know simple hand held tuners dont have the 3:90 setup as an option, but either one would be an improvement.