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-   -   Order 3.55 or 3.92 (http://www.ramforumz.com/showthread.php?t=155041)

ElRushmo 10-06-2013 09:36 PM

Order 3.55 or 3.92
 
Hey guys,

Thanks so much for all the info so far. I've learned so much in just a few days. I'm going to be ordering a 2014 1500 ecodiesel (longhorn Laramie edition) and was wondering whether to get the 3.55 (standard) or 3.92 gear ratio? The majority of the time I won't be pulling anything, so gas mileage will be my main concern (majority of the time). I'd like to buy some toys (looking at a 21 foot camping trailer and maybe some quads), so I'm also taking that into consideration. Just not sure which way to go. Some have said 3.92 whether you're going to be towing or not. Some have said the 3.92 has no affect of the gas MPG.

Appreciate the help in advance!

mmateri 10-06-2013 09:41 PM

i have 3.92's, on the hwy i avg 24mpg imperial, i love the fuel economy and the power

Arth 10-06-2013 09:45 PM

I have had both and honestly I prefer the 3.92. The truck doesn't gear hop as much loaded or unloaded. My MPG's seem to be roughly the same. I would go as far as to say the city MPG's are a bit better.

GTyankee 10-06-2013 10:00 PM

If you live in the hill country, you may want the 3.92
flat land i would think the 3.55 would be fine

the difference is about 1/2 turn on the driveshaft
the driveshaft rotates 3.55 turns per single tire rotation

i know there is some way to figure it out using math

1 tire rotation per 3.55 turns of the driveshaft is known
how many engine RPMs does it take the engine to make the transmissions highest gear (0.67) turn enough to make the drive shaft rotate the 3.55 rotations ?? at a given speed & including the vehicles weight
when it comes to math i suck

Arth 10-06-2013 10:04 PM

This whole math thing drives me to drink...

Quote:

Originally Posted by GTyankee (Post 1215830)
If you live in the hill country, you may want the 3.92
flat land i would think the 3.55 would be fine

the difference is about 1/2 turn on the driveshaft
the driveshaft rotates 3.55 turns per single tire rotation

i know there is some way to figure it out using math

1 tire rotation per 3.55 turns of the driveshaft is known
how many engine RPMs does it take the engine to make the transmissions highest gear (0.67) turn enough to make the drive shaft rotate the 3.55 rotations ??
when it comes to math i suck


Gantman 10-06-2013 10:13 PM

Well, since you're going with the 2014 EcoDiesel, coupled with the ZF8speed tranny, I would say you would be very happy with the 3.55 in this situation. Just like some owners with the 8speed with a 3.21 were saying they were very surprised how well it launched. That first gear of a 4.71 ratio is just crazy impressive. :smileup:

the persuader 10-07-2013 10:57 AM

I'd look at the 3.92 if you plan on towing with the Ecodiesel.

AzDusty 10-07-2013 03:11 PM

I love my 3.92s except how fast it launches me from a stop :)

Canadian Hemi Pride 10-07-2013 03:16 PM

if you have the option.. 3.92's are the way to go.. Especially if you do have future plans of a camper.. It never hurts.. Any milage gain from 3,55's will be off pure highway driving where it is perfectly flat. The only problem I have with my truck is the 3.55's.. It is noticible in city driving especially with my tires.. But not bad at all. If I owned a camper and didn't "borrow" a used one for a weekend from my dealership the odd time.. I would have definitely looked for 3.92's over 3.55's just because the small benefits here and there will all add up after a year or 2 of hauling.

Rygi 10-07-2013 09:47 PM

I always choose the steeper gear but not in this case. The 8 speed's tranny ratios make a 3.55 rear perform like a much much lower one. The exception would be if you were towing massive amounts. Happy with my 6 speed/3.92 because the rear gear is needed with the much taller tranny ratios.


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