[GreenD]

I have a 3.55 rear end on my '01. I'm wondering how it compares to having the 3.92 in terms of general driving and highway driving. I'd move to the 3.92 to increase the tow capacity but don't want to lose the smooth, quiet ride at highway speeds.

I noted that I'm turning 1,800 rpm at 60 mph and 1,950 rpm at 65 mph. Is it simple math, just divide the rpm's by 3.55 and multiply by 3.92? If so, with the 3.92 it'd be 1,988 rpm at 60 mph and 2,153 rpm at 65 mph. Is this right?

I'd be interested in hearing from anyone with the 3.92. I routinely drive 75 mph (not towing!) on the highway and would like to know if it'll run as smooth as my current D.

 

[tomk]

Yup, that simple! Math works.

 

[MWeed]

ratio

It runs just as smooth. This is basically the same engine Dodge has made for almost 50 years. It likes rpm's. You'll notice a difference in gas mileage, as to be expected it goes down. It'll start off a little easier due to the lower gear. You could go 4.08 for towing and help it a lot more as far as throttle response on the highway is concerned. Remember, if you have 4x4, you have to change the gears in both diffs or you'll blow out the t-case.

 

[GreenD]

Thanks for the reply. When you say same engine for 50 years, I assume you mean the 5.9? I'm going around and around this, am I OK with the 4.7 and taller gears or do I want to go to the 5.9. I like the 4.7 but my best bet is probably to go to the big engine and tow package.

 

[Kevin_Rants]

Depends on how much you tow and how often? The 4.7L will have better mileage than the 5.9 and has grunt a little higher in the RPM band than the 5.9 so, if you get the 4.7L and some taller gears, you may get what you're looking for (as long as the weight you're towing isn't exorbitant.)

 

[IndyDurango]

Thanks for the reply. When you say same engine for 50 years, I assume you mean the 5.9? I'm going around and around this, am I OK with the 4.7 and taller gears or do I want to go to the 5.9. I like the 4.7 but my best bet is probably to go to the big engine and tow package.

I believe you're correct and that he was referring to the 5.9L. Before the "Liter" craze, our 5.9s were called 360s because the engine displacement was 360 c.i. (cubic inches.) The 360 arrived in 1971 and was based on the 318 (5.2L) which started in 1967 and the 340 which arrived in 1968. The 318 shared many things from the 273 which which goes back to 1964.

If you can, get the 5.9 over the 4.7. Inbetween those on the Gen1 Ds is the 5.2. The Hemi in the newer Gen2 Ds is a 5.7 while performance HEMIs, like in the 300C and Charger, are 6.1. The 6.1 has yet to be offered in a D. I thought the limited edition '06 Durango NightRider would have got one, but it didn't.

IndyD

 

[BigRick01R/T]

Outta curiosity, has anyone installed a new Hemi in a Gen1 D? Would it fit with some modding of course. Something to think about.

 

[FSTDANGO3]

Not that I know of but there's a guy over at Dakota Durango that installed one in a Gen 3 Dak and it's completely functional, and awesome to boot!
Steve
DOC Pres

 

[GreenD]

IndyDurango, thanks for the history lesson! I guess those engineers 40 years ago had some idea what they were doing for an engine design to last that long.

I had a '98 Grand Cherokee that had the 5.2. It was an awful setup, it felt like a bad match of engine and transmission. OK on the highway, but around town it had bad shift points and was slow in roll-on acceleration. Because of it I wouldn't buy a D with a 5.2, probably not a fair comparison but I wouldn't want to find out.

I guess at this point I'm looking for an '03 with 5.9 and tow package. If I find the right deal on a 4.7 with 3.92 rear end I'll consider it as well. Thanks for all the comments.

 

[IndyDurango]

I guess at this point I'm looking for an '03 with 5.9 and tow package. If I find the right deal on a 4.7 with 3.92 rear end I'll consider it as well. Thanks for all the comments.

I have an '00 with the 5.9L, 3.92 and the tow package I'll sell ya. Everything's for sale for the right price, just know going in, my price is gonna be high!

IndyD

 

[greg]

Outta curiosity, has anyone installed a new Hemi in a Gen1 D? Would it fit with some modding of course. Something to think about.

Unless they moved the motor mounts I don't see why it shouldn't. However, that's not the end of the story. You'll need to change the brakes (you'll note that DC finally provided 4 wheel discs instead of the drums we all love from 40 years ago), suspension needs to be revisited, probably change the setting on the torsion bars, is the tranny the same 46RE on the Hemis? If I was going to do all that I'd consider trashing the auto and putting in a manual from the Dakota and by the time I'm done I could pick up a used Porsche :?

Adding more power without regard to how to control it is a recipe for disaster. But they do sell the Hemi in a crate?

Just my 2¢

greg

 

[GreenD]

I have an '00 with the 5.9L, 3.92 and the tow package I'll sell ya.
Everything's for sale for the right price, just know going in, my price is gonna be high!

IndyD

I took a look at your D, that's a nice looking setup. I'll pass for now, hopefully I'll find something more local, but will keep it in mind. Hopefully I'll find someone with a less-high price!

 

[Silver Ghost]

The Hemi tranny is a 5-45RFE - same as the 4.7. As you pointed out, the 5.9 has a 46RE.
Ignition is different - coil on plug vs rotor/cap/wires/coil and, because the Hemi has 2 plugs per cylinder, I'm sure the PCM is different or would need major reprogramming.
Of course, if there are $$$ available, anything is possible.
The 5.9 has been around since 1971, but has undergone changes through the years. There's a good discussion of A and LA motor development here http://www.allpar.com/Mopar/318.html

Joe

 

[tomk]

As a non-tower, other than utility trailers, and someone who's owned both a 5.9 and a 4.7, I have to say the 4.7/RFE is a better setup for general driving about.

But, if you tow, I believe the RE transmission (5.2/5.9) with a Martin Saine valve body is the better rig. I think the RFE tranny is at least as good as anything the competition offers, but in severe duty service, I think the shifts are too soft. The question becomes whether you want a jolt in your butt or a jolt in your wallet.

 

[SinCity R/T]

If you're going to swap up from 3.55's I'd recommend going to 4.10's instead of the 3.92's. The previous owner of my 03 BW RC R/T had some 4.10's installed and there isn't much of an rpm difference, but I can feel the low end grunt and I'm sure that would be beneficial in a heavier Durango.