3.55 vs 3.92

DurangoV8 · Apr 19, 2018

I have an 03 Durango SLT with the 4.7 and 3.55s, and I'm looking for better performance and towing capacity. What kind of acceleration and towing improvements can I see, and is it worth the price? Also, I don't mind the slight change in mpg.

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MWeed · Apr 19, 2018

3.55's are great for mileage. The 3.92's are better for low end grunt work. If your D is a 4x4 you'll need to do both axles at the same time. If your trailer is real heavy you will see an advantage. The real towing guys will chime in for sure on this. You will loose some gas mileage with this change. You will also have to get your PCM reprogrammed for the gear change so that your speedo will be correct.

Don Fox · Apr 20, 2018

DV8:

To add to the good info from Mike, the down side to such an upgrade (especially with 4x4) is that you will pay in the $1.5-$2.2K range to have the work done labor and parts. You can probably cut that by a half to three quarters if you were to find assembled axle units from a salvage Durango and install them yourself. It would not be a job for a lightly skilled person. I understand that the front axle is not much fun to remove/install.

Don

Chase300 · Apr 20, 2018

On the 4.7L FE hit will be minimal IMO.
Actually quite a few 4X4's will put in 4.56's....though I feel the 3.92's are the perfect gear for the 4.7L especially 2wd.
Gives good punch off the line, I've pulled over 7,000 lb. boats with ease and yet still can get close to 20mpg highway if I keep it around 75.

Chase300 · Apr 20, 2018

Oh, you might have the 5-45 RFE which runs a taller overdrive than the 45RFE in mine.
You could go 4.56's.
But to give you a reference with 3.92's, with OD off my RPM's are right at 3100 rpm's @ 70mph...which is peak TQ for the 4.7L so towing at highway speeds is great with 3.92's.

Don Fox · Apr 20, 2018

I don't think the 4.56 gear is an option for a 4x4 01-03 D. As far as I know, the only gears available for the front axle are 3.55 and 3.92.

Don

Chase300 · Apr 20, 2018

Factory yes...but aftermarket you can get 4.56's for the 9 1/4 rear.
Almost needed on 4X4's if also installing larger diameter off-road tires.
But stock size wheels, 3.92's work really well.

Chase300 · Apr 20, 2018

Don Fox said:
I don't think the 4.56 gear is an option for a 4x4 01-03 D. As far as I know, the only gears available for the front axle are 3.55 and 3.92.

Don

You could be right Don...forgot the front axle is a bit smaller.

MWeed · Apr 20, 2018

You really can't run larger than 31's without the risk of having to trim the front bumper, although some have gotten away with some 32's. Plus the axle thing for the front.

3.55 vs 3.92

DurangoV8

MWeed

Don Fox

Chase300

Chase300

Don Fox

Chase300

Chase300

MWeed

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