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Discussion Starter #1
OWNERS OF RAM 1500 WITH 392 RATIO:

(this is not intended to claim that 355 is better than 392, or 392 is better than 355)

I test drove a Ram 1500 today here in the Pittsburgh Pa area. The truck had 355 rear and with 20" wheels.
At just under 2000 rpm, the truck was doing 80 mph. I will test drive a 392 when the dealer gets one in, and am thinking of 392 for here in hilly Pennsylvania.

I saw the postings on mileage, and some of the mileages were just phenomenal, and others were in the 27-28 mpg range.

I am curious as to the fuel economy on the 392 rear end trucks is..... with both 17 and 20 inch wheels.

Doing the math, the 20" wheel gives you 3-3.5 mph for the same RPM vs the 17" wheel, with the 392s.

Marsman
 

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What dealer had an ED in stock?
 

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If the circumference of the wheels is different, That would mean Ram has to use a different speedometer gearing to be accurate. Interesting to put a GPS in and see if it's correct.

For 80 mph mine does 2100 rpm with the 17's and 3.55's.
 

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The speedometers are electronic. So if you change wheel or tire size you can have the ECU flashed so that the speedo is still correct. Most after market programmers give you the option to adjust for wheel and tire size.
 

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Tire and gear size were a concern of mine when I bought my '98 Chevy diesel. The best gearing option they had available for the 16" wheels was the 3.42, in my opinion. The standard one was 3.73. I chose the higher gearing for fuel economy purposes. I'm hoping I made the right decision with the 3.55 on the ED.
 

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Discussion Starter #7
Spark, if Ram offered a 373, I would get that in a second. the 17" wheel tire is 31.6 inches OD, and the 20s are 33 inches OD.

So if I get the 355 I will run 17s, if I get the 392s, If I get 17s, I may down the road get 20s to run in the summer.
 

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Is there anone who got 3.92? I thought I ordered 3.92, but truck came with 3.55 and 20 inch. I live in a very hilly the area and I found that I like how it is geared. Sure 8th gear is long, but truck determines grades pretty well and downwhifts and holds the gear on uphills. We have speed limit of 50mph here, so when driving 50-60mph truck is mostly in 6th and 7th gear. Also as you might know you can lock out higher gears by pressing Gear -. After 120 miles, mpg has been 21-22mpg without trying to be efficient.

I
Overall I find its pure joy to drive this truck abound. It handles really well and rotates in corners with less understeer than my Legqcy GT with sti rear sway bar, rce springs and Bilstein shocks!
 

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Discussion Starter #9
Andrey congrats on the truck, and I am waiting for someone with 3.92s to weigh in with their fuel economy. Also good point about the tranny gearing handling the hills/grades. Interesting and really if I end up with 355 and 17s, I will be more than satisfied. I took at 20 mile test drive yesterday, on a truck that had only 17 miles on the odometer... my observations was the ride was superb, the handling over rough roads/potholes was good, and the steering felt well balanced.
The motor weighs 500 some pounds.... I know the Cummins 5.0 with fluids will weigh in at 900 pounds.....and may be nose heavy.
This little V6 felt about perfect...
It was the best riding truck I ever been in.

Marsman
 

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Agree they do ride well. I'm not used to that from a truck and is an issue for me.

Must learn to get used to comfort.
 

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I am not hauling or towing anything right now but I live here in the mountains of Somerset county, Pa and the 3.55 are more than adequate for going up and down the hills and I have gone up the mountain from Ligonier on route 30 and had no problem. I have also climbed the mountain on the PA turnpike and it had no problem with going 72 up the mountain. I can't wait to see what this truck does when we visit my flatlander inlaw's in the state of Indiana. Everyone makes the mistake and uses there experiences with a gas motor and think that they need this with a diesel and it is just not the case. I remember Dad had a Cummins with 4.10's and all that it did was rev and rev some more. The Cummins that I traded in on this Ecodiesel had 3.42's and was just fine up here in the mountains. I would not mind driving one of these with the 3.21 and see how that does personally.
 

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With a turbo engine I personally believe it's more about reducing the load than it is reducing RPM. If you are doing mostly urban driving or hilly/twisty roads you will likely find the 3.92s as good or better for economy as you'll be loading up the motor less and spooling the turbo less, and vice versa, if you live in the country and it's mostly flat, go as low as you can get away with. IMHO

With the 8 speed I think I'd go 3.92 regardless.
 

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^^^ exactly ^^^

I get the worst gas mileage staying in higher gears and loading the motor, it loads the motors increasing boost and dumping fuel to burn in all the extra air. Along with that EGTs skyrocket. Where as If I let it down shift the RPMs shoot up but it's less load on the engine so it stays out of the boost. One of the reasons in tow/haul mode transmissions down shift earlier.
 

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Discussion Starter #14
Sean Holman editor of Diesel Power Mag said in the one article that for combined driving the 392 may/will actually get better mileage.

Penndy, I like the area you are in, we had 181 acres outside of Ligonier, beautiful, long story, but my brother owns the last 50 acres now. it was a slice of heaven up there, many fond memories. And those mountiains with the 3-5 mile grades, if the Ram is performing well, then it will perform well just about anywhere.

I am hoping folks with the 392 post their fuel mileage.

a heck of a package... after my 2006 Ram Cummins, modified motor, and suspension.... Riding in the Ram 1500, the dear wife will think she is in a Caddy !
 

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It is a beautiful area up here on the mountain. Driving this truck I forget sometimes that I am in a truck unless I come to a stop and get my whiff of diesel exhaust and the wife likes getting in this better. That being said I am not sure that it is running at peak efficiency yet and once I get this leak fixed it should be even better or I hope.
 

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Really interested in this thread. I'm waiting on my Laramie Crew cab 6'4" with a 392 rear end. Wanted the extra tow numbers vs the 355. Post those numbers folks! Mine won't be here until July 1st ish...
 

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I ordered my truck with 3.92's. I do not tow much if I do it is to tow my trash trailer to the dump. I live in Colorado and it is hill there and I want to lift my truck a little maybe 4" and run 35" tires. I believe with running 35" tires the RPM's will be around a 100 RPM's high that the 3.55 gearing would be at.
 

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You guys that ordered 3.92's. What trim and tires were you able to order. Tradesman or Outdoorsman with 17's?
 
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