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Discussion Starter #1 (Edited)
Fourwheeler had this to say about a test of a Crew Cab ecoDiesel pulling a ~7300 lb trailer:

"Our 3.0L backed with the eight-speed transmission and 3.55 axle gears was always able to maintain a minimum of 55-60 mph on our brutal test route. While ascending the steepest areas on the route, which included the 6 percent grade of the Grapevine, we had our foot to the floor and the V-6 was spinning at 4,000 rpm for several minutes in order to maintain 55 mph. On less steep sections the little diesel quietly motored along between 2,000 and 3,000 rpm, and still had enough reserve power to make passes."

When Fast Lane Trucker tests the ecoDiesel next month on the Ike Gauntlet, at higher elevation and slightly steeper 7% grade, I have doubts that the Ram will hold 55mph. This won't look good vs. the F-150 ecoBoost which easily maintained >60mph on the Ike Gauntlet. The higher altitude may not be too bad, because the single turbo will compensate some for the lower oxygen levels. It's the lower horsepower of the Ram that might hinder high-speed towing at the extremes.

Question: Will switching to the 3.92 only help low speed (0-50mph) acceleration and towing power, or will it also help to maintain speed at say 60 or 65 mph? If so, let's hope the 3.92 is used on the Ike Gauntlet for a real test of this truck's capabilities. The answer may not be easy, and may depend on how Ram has programmed the ecoDiesel to stay in its power band in combo with the 8-speed transmission and the different axle options.
 

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im not super smart when it comes to this stuff but wouldn't a higher number mean longer gears overall? or do i have it the other way around?
 

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Other way around. They're really 3.55:1 so With 3.55 the motor turns(crank shaft) 3.55 times to the wheels 1 revolution. With 3.92 the motor spins 3.92 times to the wheels one so for a given road speed (number of tire revolutions) the higher the engine speed.
 

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Then throw in what tire size can do (17" vs 20")

I've been trying to decide on right combo, and came across this:
Tow Ratings for Dodge Ram 1500 with 20" OEM Wheels

Still trying to figure this out. At first I was thinking 17" and 3.55, but I do like those 20" filling out the wheel well--so I might have to think 3.92.

Thoughts?
IF there is any real de-rating for 20" tires I think the reason would be the load rating of the tires.
I'm not sure what load range is for the 17 and 20's but the 17's are available up to load range E.
Also one other item to consider is the limited choices in 20" tires when it comes time to replace them. I know I can replace my 17's for about 2/3'rds the cost of my dads 20's.
 

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IF there is any real de-rating for 20" tires I think the reason would be the load rating of the tires.
I'm not sure what load range is for the 17 and 20's but the 17's are available up to load range E.
Also one other item to consider is the limited choices in 20" tires when it comes time to replace them. I know I can replace my 17's for about 2/3'rds the cost of my dads 20's.
But the 20" look cool!
 

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load ratings is a very important metric. Especially if you're going to be a regular tower, low pro 20's are going to wear much faster than a thick walled 17. Not to mention the significant price gap between tires for a 20 inch rim and tires for a 17...

Just another additional cost to think about...
 
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