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Discussion Starter · #1 ·
Well we bought a 01 D with the 4.7 and the 45rfe tranny . 82000 miles , 3.55 gears and apparently , stock size tires (265/70x16). Factory tow package with the factory tranny cooler.

The engine and tranny seem very smooth , and we have noticed nothing out of the ordinary with our local driving.

Over the weekend , we took our first road trip in the D to Omaha for a wedding . Going south we were bucking a 30+mph headwind , and with 5 people in the rig it was really sucking gas , around 12 mpg . But what concerned me was , running on perfectly flat ground with the cruise set at 70 , I notices a few times it seemed like the tourque converter was partially unlocking . The engine would rev up a couple hundred rpms whilst the speed appeared to remain constant .

On the way back north the next day with about a 20 mph tailwind , we knocked down a good 17 mpg , that felt alot better ! But we were gettin with the program and running 80 mph on I-29 , once we got back in god's country (SD). There are some moderate hills , and the tourque converter would definately unlock easily if you gave it enough throttle to maintain speed . It would rev up 400 rpm or so , then lock up again after the hill was cleared.

Does this sound like normal operation for this transmission under those load conditions ? Or are we looking at something that neeeds attention ? As far as I could tell , nothing got hot , and the tranny fluid stills looks nice and fresh . No check engine lights showed up.
 

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Your talking about the truck dropping down to third rear and then resettling in OD after a short stint right? If so, then the extra load inside and the 3.55's leave your tranny searching for the right gears to keep you at speed. Do a search on 4.56 gears and you'll read a bunch on the same topic.
 

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Keystoner
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there's a couple of sensors that get dirty that could be doing that also
TPS
IAC

both sensors on the throttle body.

make sure your transmission fluids are topped off also. Your bands might need adj.
Just a few things to look at
 

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Discussion Starter · #5 ·
Thanks for the hints

JT.......I don't believe it was dropping into 3rd on the hills at 80 . It was coming up maybe 3 or 400 rpm which I don't think was enough to be getting all the way into 3rd. Seemed like just enough to unlock the tourque converter (on some of the hills).

Interesting about no bands in this transmission . I didn't know that either .
 

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Keystoner
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JTquint said:
45 RFE's are fully electronic...., no bands.
thanks quint. Didn't know that....
 

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JTquint said:
Your talking about the truck dropping down to third rear and then resettling in OD after a short stint right? If so, then the extra load inside and the 3.55's leave your tranny searching for the right gears to keep you at speed. Do a search on 4.56 gears and you'll read a bunch on the same topic.
Agree, its the 3.55 gears.....you'd be much better off with the 3.92's. I think the 4.56's are too much for a Durango, which is quite a bit lighter than a 4door Ram. I'll bet you'd see better mileage as well. I can tell you mine gets better mileage than what you stated. Plus with the 3.92's the truck has some decent acceleration and won't kick down out of overdrive for small hills.
 

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Perfectly normal. Our does that too. The 3.55s are tall with the .69 O/D ratio. The 4.7 likes to run. We get 20mpg consistantly running 70mph but only 12mpg in town. Definately a hwy gear. After four Cummins diesels in my Rams, I like the ability to downshift and "run" when it needs or wants too. My Hemi powered '05 Ram does the same and will do it from 3rd while towing our 5th wheel. It unlocks the torque converter for about 400 more rpm. If it downshifts to 2nd, it'll run 4200+rpm and man does it sound good!
 
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