Is the 3.55 rear end with a 5.7 hemi and factory 20's adequate. And it that the best mix for top MPG?

 

yes on the mpg's.

 

2wd or 4wd? If 2wd then the 3.21's are your best bet for milage. Rated at 20 highway with the Hemi and 3.21's.

 

^^^ What he said.

3.21's are proving to be the best. The proof is around in this forum.

 

3:55 gives you enough to pull a trailer and is still faily good on gas on the highway and city as far as I am concerned, mine is doing well. Now that gas prices are going up again I guess we will all start second guessing our dumbass selves for buying a HEMI

 

Even though the sticker gave the 4.7L's a 1 mpg advantage over the Hemi's across Chyrsler's range of vehicles, I had several friends with 4.7L Commanders and Hemi Commanders where the Hemi's got better 'real world' mileage than the 4.7L's. The same goes for Durangos and Grand Cherokees. I believe the 4.7L was recently redesigned and got a HP and torque increase as well as the Hemi though. I'd be curious to see if the real world vs. sticker mismatch continues on in the new Rams... Anyone know someone with a 4.7L Ram?

 

Yeah, I have a 4.7 09 Ram. I'm getting 20mpg with 3.92 rearend. My commute is 80 miles roundtrip on mostly two-lane country roads. Recently towed my 74 Duster to MD and back to NC getting 13mpg.

 

I believe both the 3.21s and 3.55s were rated at 20mpg hwy, however real world numbers are definitely proving in favor of the 3.21s. So, if you have a 2wd and don't plan on towing, the 3.21s are the way to go to improve mpgs. The 3.92 or 4.10s are for off the line acceleration or 4 wheeling and the 3.55s are a good compromise in between for a 2wd that occasionally needs to tow.

 

n00b question alert:

what gears do i have in my 09 1500 sport?
its a 5.7, 4wd, dual exhaust. not sure if any of that matters.

 

I've got the 3.21's and plan to tow. Tow rating with the 3.21 is only 5700lbs, but that is fine for what I tow. Funny thing is that my wifes little v6 sorrento is rated for 5K.