hey guys i was thinking about putting in new gears into my truck but i wanted some sdvice first. i was doing some research and i think i want to go with either 4:10's or 4:56's, but my question of concern is what will that do to the tranny and would it affect the speedo ?

 

There is a guy on Dodgetrucks.org that went from 3.55s to 4.56s in his 02 QC and swears he has more performance and gets better mileage to boot. I would attempt it, but my 04 4x4 already has 3.92s and would be pretty expensive swaping two sets of gears.
If you go to that site, his name is Air Ram and posts quite frequently.

This is a quote from him....

"BUT I must say HANDS down if I had to chose ONLY ONE I would chose the 4.56 rear gears... They get me off the line in a hurry, tow like there is NOTHING behind me and get 2-3 MPG better over the 3.55's..."


Also, the computer senses the gear change and compensates, so your speedo will be fine.

 

How would that give him better gas mileage? At freeway speeds he would be revving higher, right? Do the gears make it that much easier for the engine under acceleration?

Any explanation for this?

 

I would think that at freeway speeds you would get worse MPG, but if you drive alot of street I think it would help some because you are able to get moving off the line with less effort.

 

Guys, from 3.55's to 4.56's I gained 300 RPMS at 60MPH... Its not RPMs alone that determine fuel economy, as a matter in fact the RPM’s have a SMALLER role on fuel economy than everyone thinks. Its the load on the engine at any given RPM that WILL determine how much fuel is needed. The 4.56's get you rolling off the line with LESS effort/load which means less fuel. And because of the .67 overdrive and 30"+ tall tires DC has blessed us with we are able to travel on the highway more efficiently with less effort/load which means less fuel. At 65-70MPH your will have approximately 350-400 more RPM’s BUT less load on the engine at that speed... so you will consume less fuel.

As for top speed I have been WELL over the 120MPH on the Speedo with the 4.56's installed. If I had to guess I would say over 140MPH... or "L1" and I was only about 4200RPM@140MPH that speed when I let off the gas. The 4.56's are a WIN WIN mod and there is NO good reason not to get them installed.

Do your homework and listen to those who have done the 4.56's... The only people who will tell you NOT to do the 4.56's or that they are too much gear are the ones who have no experience with 4.56’s in the 3rd Gen Ram. The 4.56's in our 3rd Gen Ram are not the same as 4.56's in a NON overdrive Car/truck with short 26" tall tires... The ONLY reason 4.56's are PERFECT for the 3rd Gen Ram is the .75/.67 overdrive and 30+ inch tall tires.

And the fun factor alone is worth the price of admission.

SPEED SAFE, AIR RAM

 

air ram where did you get your gears at ? and if you dont mind me asking how much did it cost to get them installed ? thanks
this is one of my next mods along with headers, bigger tb, and power wire and scoop.

 

getting ready to put some bigger tires on my truck as well ... guess i'm gonna have to look into some gears too

 

Is this an accurate statement? How does the computer sense the gear change?

 

Speedo on our trucks is affected by tire rotation, not gear rotation, as a result, the changing of gears makes no difference. By contrast, the change in tire diameter will require a speedo adjustment.

Also, the performance difference in going to 4.56 gears is night/day. You will achieve better mileage in town as you will not have to give it as much throttle to get the same acceleration/speed. It's usually a given that you lose mpg's at highway speeds, but most modern V8s have a "sweet spot" where there is a perfect balance between performance and mpg's. Not sure where it is in the 4.7s, but the Hemi's are in this zone between about 2100 & 2500 rpms. So in almost every instance I get better mileage cruising at 70 mph with my 4.56s at 2200 rpms than when I had 3.92s and was at 1900 rpms at the same speed.
Also in my case, 3.92s were not cutting it whan I lifted and went to 35" tires...

 

Yeah, I put 4.56 gears on and my highway millage went up. And I added a lot bigger tire. So I would guess on a truck that was just doing the gears with no lift and no bigger tires your looking at getting 3-4 maybe 5, mpg on high way. I know I get 3 mpg better on highway with the gears when I baby it.