I am thinking about getting a new QuadCab with the Hemi since my '02 Ram has over 162,000 trouble free miles on it. The Ram 1500 4X4 I have now has the 3.55 gears and I want that in the new one. Is that the best choice for the best fuel mileage with the Hemi with Multi Displacement or would 3.73 or 3.92 be better?

 

3.55 IS THE WAY TO GO FOR BEST MILEAGE PER GAL. UNLESS YOUR DOING ANY TOWING.I THINK MOST HEMI'S COME WITH 3.92'S

 

I disagree with that through my own experience and that of others proves otherwise. 3.55 will get you worse fuel economy than the 3.92's... This is because of the weight of the truck. 3.55's are not enough gear to get 6,000+lbs going from a rolling start efficiently. And you will consume more gas just getting rolling. Another issue the owners with 3.55's are having is the fact that the 3.55 is so high that it can not hold overdrive going up a slight incline... this causes the engine to down shift out of OD to get the needed power to do the job... but with 3.92's this will happen less often.

I personally had 3.55's in my 2002 dodge Ram with the 45RFE. I swapped from the 3.55's to the 4.56's and saw an average gain of 2-3MPG with most of the driving being done at 65MPH.

On a NON overdrive vehicle I would agree that 3.55's would be best... but since your new truck will have the 545RFE with the .67 overdrive you would be better served with the 3.92's... AND it would be wise of you to take it in to your local gear shop to have 4.56's installed!

SPEED SAFE, AIR RAM

 

That is some good points Air Ram. Just wondering if the Multi Displacement will shut the four cylinders off at a given rpm or at some point when a load on the engine is reached. I looks like to me that turning more rpm's with less load on the engine would give better fuel economy. I sure would like to get some reports from those that are running the'06 Hemi with Multi Displacement.
Thanks

 

And dont forget about the "FUN FACTOR" the 3.92's will have over the 3.55's.... there is no good reason to get the 3.55's unless you like driving a slug and poor fuel economey.

SPEED SAFE, AIR RAM