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Discussion Starter #1
Hey guys,
Well I have now driven a 3.55 rear and a 3.92 rear Ecodiesel and I have to say for the type of driving I do ( only time I go over 60 is on the highway which isn't often) I think I will be getting the 3.92 it just felt like it worked the truck way less on hills and on the back roads. I was able to get 27 mpg on the 3.92 rear and on the 3.55 it got 25mpg. What is your guys opinion on the two rear ends?
All the Best
 

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I ordered 3.92 because i do a lot of city driving and i plan on getting larger tires than stock
 

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The forum is mature enough that this topic has been discussed in depth. Just browse subjects or do a search for "ratio." At this point we are waiting for more real-life reports with both ratios to better judge power response, shifting and fuel economy. My own opinion is that they are close enough together that differences will be subtle. The basic design is optimized for 3.55 with 3.92 intended for pulling heavy loads.
 

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Discussion Starter #4
Apologize for not searching first, feel free to shut this thread down.
Thanks!
 

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Maybe I've missed an earlier thread but yours is the first comparision I've seen where both trucks were actually driven.Just what I wanted to hear.I drove both ratios with Hemi and also think there's a big differance.Thats why I'm getting my EcoD with 3.92's
 

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I agree with TMorgan there has been many threads of this topic, but this is the first real comparison that I've read. If this is an issue maybe make an official stickyed ratio thread
 

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Judging fuel economy is tricky because it depends on so many factors. Without identical test circuits, conditions and trucks (except for axle ratios) as well as an accurate measurement (not the average readout from the EVIC) comparisons such as made by the OP are almost meaningless. We really need some detailed, long-term results from owners. Also, transferring results from a Hemi to an EcoDiesel is very questionable because the engines have completely different power curves.

The best data point I have so far is a Ram rep who drove the trucks thousands of miles and preferred the 3.55 for its economy and shift points. He thought the 3.92 did not match the power band as well and served little purpose unless the truck was towing at max capacity or had oversize tires (>33 inch). Time will tell.
 
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Apologize for not searching first, feel free to shut this thread down.
Thanks!
No worries, not everyone has time to search forums thoroughly. It's quite informal here, anyway. :p
 

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The guys at Diesel Power preferred the 392 for day to day driving. I am sure either will run fine, with the tremendous 8 speed making up the difference in all but the top gear....
I'll probably go with the 392... I drove the 355 last week at a dealer near home, about 30 miles North of Pittsburgh.. the truck had 355s and 20" wheels. At 80 mph the motor was not even turning 2000 rpm...
It's personal preference.... 355 probably better all around economy.
392, better drivability, little more performance, better towing... and on the economy, just slow down a little and it will do fine.
 

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This debate will go on forever. I don’t sustain anything over 75 on the highway for very long; it is no fun getting pulled over for speeding. I’m leaning towards the 3.92s since I want to run 17’s with 33”-34’s. A lot of my other driving is mixed, stop and go traffic, 2 lane roads, off road sometimes etc. The .67 ratio in 8th is pretty tall.
 

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Some western interstates are now posting 80 mph sections, Utah has a pretty long stretch around 80 miles or more. Nevada is also considering or has increased sections to 80 and last I heard Wyoming was considering 80 for some sections. Actually for some drivers these are just guidelines for speed, just like anywhere else.
 

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1374513132000-XXX-12182012-HWY130-469-1307221314_4_3.jpg

In Texas we've got some 85 MPH limits and traffic does 90 MPH so 3.55s for me
 

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Damn! Doing 90? That must be a thrill. But then again, fuel mileage must take a dump, gearing or no gearing.
 

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90 is 150km/h they take your vehicle away for that here!! And your licence for a week! That's so awesome you guys have that limit yet another reason America is better than canada!
 

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View attachment 431

In Texas we've got some 85 MPH limits and traffic does 90 MPH so 3.55s for me
There's a reason Texas had 3000 traffic fatalities in 2010. That's nearly 12 per 100,000 people. About 42% involved alcohol. Speed and alcohol are a bad combination.

Wyoming is the worst state for fatalities at over 27 per 100,000 people. On the theory that faster is safer, they are raising some posted speeds to 80 mph in July.

As they say, it's all fun and games until...
 

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Germany which had no speed limits on some sections of its highways is one of the safest roads in the world. It's about the drivers not the roads. The speed limit around here is 60 and there's at least one fatality every week.
 

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Let's hear it for lcr!! Couldn't have said it better myself! Here in the toronto area almost 50 percent of people have been born outside canada, no jokes Google it! And the driving is unreal some of the stuff I have seen would give you night mares! Lol a lot of people used to driving in countries with no real laws methinks....
 

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I personally have never driven on the autobahn but I have been in a car when on it and I never saw any tailgating everyone stayed to the right except to pass, always left lots of room around other cars. You could look down the left lane on the hwy and it was empty except when a car went around us....just amazing courtesy, flying along at 200+km/h was no big deal at all
 
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