I have a 2006 Quad cab with Hemi 17" wheels 2 Wheel Drive 3.55 Ratio. I drive to work around 55 MPH, the problem is that it kicks in and out of over drive and MDS all the time. I need a different gear so it will stay in OD and MDS at road speeds between 45 to 60 MPH so I can get better MPG. Also When I buy new tires I will go 2" taller. What Gear Ratio do Ya'll think.

4.11
4.56

Also for the people that have done the gear change does this have adjusting nuts or Shims for the carrier.


Thanks

 

Depends on the overall OD of the new tires. Mine has the 20" wheels and tires that are about 33" tall I think and mine has 3.92 gears, so I would say 4.10.

 

I don't understand how it can be kicking in/out of overdrive and MDS at 55mph. That just doesn't make sense. The rpoblem is that you are constantly changing your foor position. seriously. MDS will not kick in unless there's flatland, your foot is still or your going down a hill. There's no way overdrive can kick in/out under those conditions. Overdrive kicks in/out when you put you speed up or slow down. MDS isn't active in either scenerio. I just think that by you going to a different gear, voiding the diferential warranty and what ever they come up with along with the added cost of doing that, woun't be worth it in the end. Think about it, your talking about putting numerically higher gears which in return will increase gas consumption. Bigger tires which will increase gas consumption. Yes the pair together will be effective, but still worse than you are off with mileage right now.
Now, I must say I think that the MDS causes your vehicle to seem like it's in/out of overdrive more than the truck actually is. eliminating the mds will probably yield you better gas mileage in around town. I actually get better mileage on the highway in tow.haul mode than I do with mds kicking in because I have to press the gas much further to even move which causes the truck to downshift constantly. Bigger tires and keeping your stock gear size will yield the best MPG's and will put you into a diff. MPH shifting pattern. I would try the tires before your gear change. Since you will need a programmer for the gear change and maybe some other reasons, get it and turn that mds off and see how your truck acts.

 

I went from 3.55 to 4.56 not only will MPG get better, but you feel like you have a lot more power. Best mod yet.

 

ANY change in tire size larger than stock and I'd go straight to 4.56's and not even consider the 4.10's...

 

I went from 3.55 gears to 4.56 gears with the stock 31.5" tall tires and gained 300RPMs@60MPH and 3-4MPG...

Also it does NOT void your drive train warranty and if anything it will extend the life of your transmission by moving the stress from the transmission and adding mechanical advantage to the rear end...

Also, you do NOT need to reprogram for changing gears... the speed sensor is located on the housing. One revolution will always be one revolution... and that's what it counts.

BUT you could get the Superchips 3815 and adjust for tire height... and add some POWER to boot!

DONT FEAR THE GEAR!

SPEED SAFE, AIR RAM

 

4.56... Dont even look at the 4.10's

 

OK First off. How can you possibly gain MPG's going to a numerically higher gear ratio? 2nd, if you gain rpms, then you altered the revolutions of the driveline. You do need to correct the speedometer because one revolution is not one revolution! You have this whole thing backward bud. Going from 3:55's to 4:56's will make your engine rev at a higher rpms and cause your mpg's to go down. It's simple physics! I gunno where you and OEfootball got your information from.

For example, my mustang had 3:55's stock. At 80mph it ran 2250rpms. I installed 3:73 gears and at 80mph it ram 2650rpms and my gas mileage went down 1-2mpg on the highway. I also had to change the speedo gear that was installed in the transmission.

Ohh, also, you will void your warranty on anything associated with the rear end. Guaranteed!
And why, please tell me why....You would possibly need to change for tire height if one revolution is one revolution???? Because it changes the gear ratio! A taller tire lowers your gear ratio! If you had 3:92 gears with a set of 20's and then put on some 15" rubber with the same profile, you have just simulated 4:56's with 20's. I know you don't understand, but it's the truth.

 

Dog, you are all wet on this one!
First: NO speedometer recalibration is needed on a Dodge Ram, because unlike your 'stang, which reads speed off a gear in the transmission, in the Ram, it's calculated right off the ring, so the final drive ratio does not affect the speedometer. Changing tire size is the only reason to change the speedometer calibration. Trust me I've done it and verified with a GPS!

Second: Everyone I know with a truck, be it Dodge, Chevy or Furd who has done a gear swap, has reported a positive mpg gain, at least in city driving conditions. This is because when the engine rpm's are higher, it is not necessary to give as much gas when starting from a dead stop or accelerating from a slow speed. Contrary to opinion, even highway mileage is not drastically effected (unless you cruise at say 75 mph or more where you will see a minimal mpg loss) because the Hemi seems to have a "sweet spot" from about 2100-2300 rpms where mileage seems to be a tad better than just below those rpms.

Third: Taller tires DO effect your gear ratio or at least your "effective gear ratio". When putting 35" tires on a truck calculated to run at a ratio of 3.92 with 31.5" tall tires from the factory you would need 4.56 (well 4.45 to be exact, but the closest made would be the 4.56s) to maintain that "effective ratio" of 3.92 and still retain any semblance of factory acceleration and power with those bigger meats.

 

Thanks Everyone, sound like the 4.56 gear set is the right one. 95% of my driving is in back country roads and pulling a trailer for my Baja. where is the best place to get a 4.56 gear set ?


Thanks