Hi I have a '06 3.0 5 speed regular cab
Have noticed when driving 70mph my engine rpm is 2750
I have stock tires and everything else is stock
The tag on my rear end says I have 8.8 with 3.73 gears
Would my mileage improve if I changed gears to say 3.27?
would it b worth it? Or would it just turn my truck into a dog like the 4cyl?

 

It wouldn't be worth it.

 

U think it would just b underpowered
Seems like the truck was made to just go 55mph
Instead of 70

 

I used to drive extensively over the highway with my 3.0 and found that anything over 65 decreased my mileage.Generally lost 2mpg at 70 and about 3mpg at 75.The air just doesn't flow well over these trucks at those speeds. I would average 25 mpg at 65.
Keeping the paint clean and well waxed made a bigger difference than I thought. Mileage always went down from Monday after cleaning and waxing on Sunday , To ending on Friday with a filthy truck.I was averaging ~300 miles per day.By Friday It was down to 22mpg at 65.

 

Otrtech what gears does your rear axle have?

 

looks like i need to wash the truck again, and slow down on the freeway...

 

Speed is te killer. Also laying into the throttle is another huge thing people don't think about. With a stick you might be pushing harder and not notice when shifting. Try low speed take offs and shifting clean and smooth at lower rpms rather than let it rev out.



* I tried this with with my stang and it showed improvement. But anyone that knows me would know it killed me to try and do it for a full tank.

 

the real killer is changing speed. obviously acceleration, but braking too. braking causes loss of momentum. not saying don;t brake, just brake smarter.

 

Your right these truck were built for slower speeds like 55... if plan to keep going 70-75 then I'd suggest investing in aero mods before gearing.

 

that's why i can't bring myself to slow down on the freeway... but i did get a mileage increase... changed the fuel filter and now i run the entire interstate at 3000 RPM in 5th instead of needing to use 4th and 35-3800... of course i still lose speed on the hills, but not nearly as bad

EDIT: and i do take off not very hard, shift at 2000 RPM and i am gentle about 85%of the time

 

4.10 limited slip.

 

Get a scangauge / ultra gauge and you'll know what really works driving and speedwise on the hiway.

 

oh... i know it would really benefit me to slow down on the highway... i had to follow someone to get somewhere and they drove like 60 on the interstate... on that tank of fuel i averaged 25.6 mpg... i just can't take going that slow... we got passed uphill by a UPS big truck with two trailers on... and i thought a Prius was gonna rear end me at one point...

 

I usually go close to 70. I agree with getting an ultragauge too, my eye is always on my mpgs.

 

No one has ever been passed by a UPS truck driver. They are paid by the hour will not speed.

 

he wasn't speeding... i was going less than 60 when he passed me... limit was 70... i didn't enjoy going that slow, but i got great mileage...

 

Man that is embarrassing


FWIW, I will get better mileage if I beat on it till over drive. Especially in the city.

 

i was following my friend's grandfather to his graduation from the MCA and couldn't pass due to not knowing where i was going... we went between 50 and 65 on the interstate where i usually go 75 to 80... i was embarassed to be going that slow... the 25 mpg wasn't worth the embarassment, so on the way home i passed him and traveled at my usual speed...

 

I am going to change out the gears in my rear end
I have done the math and currently with my 29in tires
3.73 @ 70mph runs at 2900rpms
3.08 @ 70mph runs at 2400rpms
Should get me better than my current 21mpg (on a good day)

 

Ok FYI
My 3.0 sport had 4.10 gears @ 19mpg
Changed them out to 3.55 after three long highway trips to test it
now I get 25mpg
Best 200$ ever spent

 

Thanks for the update that's a great improvment

 

I've got an 06 sport with 4.10 gears in the rear. How difficult is it to change them out to the 3.55? Will it affect towing much? Thanks for the help

 

I got mine from jegs $150 + $40 for 3qts synthetic gear oil
took about 2hrs to actually do it however I had to take the pinion to a machine shop to have the bearing pressed off n put on the new one for $25. It's kind of a guessing game to determine which shims u need
Might b better to have a shop Doit if u have never messed with gears b4
Requires a special tool to check the free play between the gears, I didn't have this tool so its not exact n it makes a little high pitched tone at 45mph - 60mph with the radio all the way down

 

Ended up just rearranging the shims n got lucky as for towing I pulled a 12ft flatbed trailer b4 I changed the gears with 10mph head wind 65mph top speed lol. I havnt tried it since I put the higher gears prolly is gonna suck but I had the truck 4yrs now and only towed something 2x ever. keeping the gears on the shelf in case I ever wanna put em back in, next is gonna b underdrive pulleys n exhaust, see if I can get the pulling power back

 

yeah, you aren't gonna have pulling power with a 3.0 and those 3.55 gears... even if you do headers, a superchip, airbox mod, an exhaust, those u/d pulleys, and an e fan... but all those will help economy as well and will give a little back