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Custom Dodge Ram Performance Mods - Engine - 3.6 Liter Pentastar V6 Discuss modifying your Dodge Ram with Performance Parts and Accessories!
Factory Spec: 3.6-liter V6 engine - 305 horsepower, 265 lb-ft of torque.


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  #21  
Old 01-31-2013, 08:23 AM
xmanofsteel xmanofsteel is offline
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Originally Posted by snrusnak View Post
I'd suggest 3.55 or 3.92. I have 3.55 and easily get 20+mpg. I hauled ~1200 lbs in my quad cab from FL to TN to AR and back to FL last july in 110 deg F heat, cruising at 75mph most of the trip(through all the mountains) and got 20mpg avg over the 2600 miles. Best I've done is like 22mpg unloaded at a slower speed on flat ground. Like I said I am switching to 4.10's because I almost never cruise above 70mph and NEVER cruise above 75-80mph and from the experimenting I've done it won't effect my mpg. I just won't be able to get 22mpg at 75mph anymore. But my city mpg will improve.

If I were getting an 8 speed I'd still choose 3.92. At the least 3.55. I wouldn't even consider 3.21, just doesn't make any sense, it's like shooting yourself in the foot.
Thanks for your input. I'll probably end up going with the 3.55's, just because I don't really plan on towing, so the extra few MPG may be better for just my daily drive.
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  #22  
Old 01-31-2013, 10:03 PM
rpinsc58 rpinsc58 is offline
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mine came with 3.21 and it has plenty of pickup. i haul around 300-400 pounds of tools and ladders and drive 70 mph for 4-5 hours straight. i get anywhere from 21.5-22.5 mpg. my last truck was a 2012 4x2 4cyl tacoma 5speed manual and it got 20-21 mpg under the same conditions. so just to be clear.... the dodge ram, with twice the horspower, 2 extra cylinders, and 50% more total weight, gets BETTER gas milage than the Toyota.

and thats why i bought it
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  #23  
Old 01-31-2013, 10:36 PM
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mine came with 3.21 and it has plenty of pickup. i haul around 300-400 pounds of tools and ladders and drive 70 mph for 4-5 hours straight. i get anywhere from 21.5-22.5 mpg. my last truck was a 2012 4x2 4cyl tacoma 5speed manual and it got 20-21 mpg under the same conditions. so just to be clear.... the dodge ram, with twice the horspower, 2 extra cylinders, and 50% more total weight, gets BETTER gas milage than the Toyota.

and thats why i bought it
You have a hemi?

Yeah my ram gets like 16-17 city and 20+ hwy with ~340hp and my s10 4 cylinder manual trans with 120hp got like 18 city 24 hwy. I'm pretty happy with my mpg.
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  #24  
Old 02-02-2013, 02:42 AM
mikennrg mikennrg is offline
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Quote:
Originally Posted by snrusnak View Post
I'd suggest 3.55 or 3.92. I have 3.55 and easily get 20+mpg. I hauled ~1200 lbs in my quad cab from FL to TN to AR and back to FL last july in 110 deg F heat, cruising at 75mph most of the trip(through all the mountains) and got 20mpg avg over the 2600 miles. Best I've done is like 22mpg unloaded at a slower speed on flat ground. Like I said I am switching to 4.10's because I almost never cruise above 70mph and NEVER cruise above 75-80mph and from the experimenting I've done it won't effect my mpg. I just won't be able to get 22mpg at 75mph anymore. But my city mpg will improve.

If I were getting an 8 speed I'd still choose 3.92. At the least 3.55. I wouldn't even consider 3.21, just doesn't make any sense, it's like shooting yourself in the foot.
I realize you probably haven't seen the gear ratios between the two.

65 rfe 1st 3.00 2nd 1.67 3rd 1.50 4th 1.00 5th 0.75 6th 0.67 Reverse 3.00
8sd 1st 4.71 2nd 3.14 3rd 2.10 4th 1.67 5th 1.29 6th 1.00 7th 0.84 8th 0.67 Reverse 3.30

At your 75 MPH figure the eight speed with a 3.21 would turn approximately 2866 RPM. With the 3.55 it would be turning 3150 RPM. Now with the 6 speed a 3.55 would turn approximately the same 3150 RPM. This is all using this calculator. http://www.csgnetwork.com/rpmcalc.html

Now for 1st gear in both at 15 mph the 3.21 8 speed is turning 2875 rpm making towing easier with the 6 cyl and that rear end. The 6 speed with the 3.55 is turning 2025 rpm at 15 mph

I've towed over 2000lbs. often with a v-6 dakota that had much less HP than the Pentastar and a terrible first gear ratio. If he's only towing a couple jetskis every once in a while the 3.21 will be fine. If he got the 3.55 his computer would skip 1st for most driving from what I've heard.

Last edited by mikennrg; 02-02-2013 at 02:48 AM.
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  #25  
Old 02-02-2013, 07:08 PM
xmanofsteel xmanofsteel is offline
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Quote:
Originally Posted by mikennrg View Post
I've towed over 2000lbs. often with a v-6 dakota that had much less HP than the Pentastar and a terrible first gear ratio. If he's only towing a couple jetskis every once in a while the 3.21 will be fine. If he got the 3.55 his computer would skip 1st for most driving from what I've heard.
Now I'm torn...

My drive is pretty well all highway / country roads, so I'm rarely going slower than 100 km/h, usually closer to 110 or 120. I do have some pretty big hills, and what I thought I had read before that the 3.21's wouldn't handle the hills as well and would actually cost me more money in gas than the 3.55's. That's kind of what I was going off of, but I assumed that it was for the 6 speed transmissions. So I wanted to know about hte 8 speed to see if there was still this issue or not...
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  #26  
Old 02-02-2013, 11:34 PM
rpinsc58 rpinsc58 is offline
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i just spent 3 hours cruisin back roads at 55-60 mph without any added weight and averaged 27.5 mpg no drafting
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  #27  
Old 02-02-2013, 11:54 PM
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LOL at rpin...

mike...your math is not correct. I am very familiar with the ratios of the 45rfe/545rfe/65rfe, the 66rfe, the 68rfe, and the new 8 speed. I don't really know what your point is, I understand the rpm differences at different rpms. The problem is that people think lower rpm = higher mpg, which is only true to a certain point. Try cruising at 600rpm and see how your mpg is with the engine lugging. I have personally verified that I get he same mpg at 70mph in 5th or 6th gear with 3.55's.

And your math is way wrong, BTW. For your calculations to be correct you need to assume a tires size of ~26", which isn't even remotely close to what's on these trucks. At 70mph in 5th gear I am at ~2,000 rpm. At 70mph in 6th ge I am at ~1700rpm. I get the same mpg either way.

Yes 3.21 will be ok, but you won't get better mpg if you don't cruise over 75mph. So why shoot yourself in the foot? Just get 3.55 or 3.92 and get the same mpg(better in the city, actually) and have more power on demand(and less strain on the drivetrain).
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  #28  
Old 02-03-2013, 10:51 AM
xmanofsteel xmanofsteel is offline
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Quote:
Originally Posted by snrusnak View Post
Yes 3.21 will be ok, but you won't get better mpg if you don't cruise over 75mph. So why shoot yourself in the foot? Just get 3.55 or 3.92 and get the same mpg(better in the city, actually) and have more power on demand(and less strain on the drivetrain).
Now I'm thinking of getting the 3.92's just because...lol
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  #29  
Old 02-03-2013, 11:32 AM
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If I may.... I got a call from my dealer on Friday, so to let me know the 3.92 was no more available for my order (4X4 Outdoorsman w/ V6). Mind you, I placed that order way back in early November

Now it seems the choices are either 3.21 or 3.55 only, so I went with the 3.55... No need to chug w/ moderate towing when coupled with 3.21. I believe optimum torque will be more easily exploited with the 3.55...
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  #30  
Old 02-03-2013, 03:43 PM
mikennrg mikennrg is offline
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Quote:
Originally Posted by snrusnak View Post
LOL at rpin...

mike...your math is not correct. I am very familiar with the ratios of the 45rfe/545rfe/65rfe, the 66rfe, the 68rfe, and the new 8 speed. I don't really know what your point is, I understand the rpm differences at different rpms. The problem is that people think lower rpm = higher mpg, which is only true to a certain point. Try cruising at 600rpm and see how your mpg is with the engine lugging. I have personally verified that I get he same mpg at 70mph in 5th or 6th gear with 3.55's.

And your math is way wrong, BTW. For your calculations to be correct you need to assume a tires size of ~26", which isn't even remotely close to what's on these trucks. At 70mph in 5th gear I am at ~2,000 rpm. At 70mph in 6th ge I am at ~1700rpm. I get the same mpg either way.

Yes 3.21 will be ok, but you won't get better mpg if you don't cruise over 75mph. So why shoot yourself in the foot? Just get 3.55 or 3.92 and get the same mpg(better in the city, actually) and have more power on demand(and less strain on the drivetrain).
It's not my math it's from the site I listed in my post. It doesn't take into account overdrives from either transmission, but you get the point.

You obviously haven't looked at the gear ratios. The 8 speed gear ratios make a 3.21 like the 3.55 with the 6 speed. If you think the truck is going to lug in 8th all the time you're an idiot. 8 speeds give better mileage because you always have the optimum gear for every situation. The 3.55 will most likely make 1st obsolete and possibly make highway MPG less at higher speeds.

I've towed many miles with a 210 HP V6 and terrible gear ratios compared to the 8 speed/3.21. A lot of it with hills. He'll be fine with the 3.21 trust me.
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