Regearing to 3.21 Like the RAM for best MPG

[dcmdon]

So I may owe you an apology.

I was about to write. " Yes, but still you are talking about a completely different engine with a completely different torque curve". Since normally aspirated engines tend to run most efficiently at their torque peak RPM. (gal per hp per hour)

But then I realized you may be talking about a Ram with a pentastar engine.

If you are talking about a ram with the same engine with the same transmission ratios then you may have a point.

Though I still think that the transmission may just compensate by running around in 7th gear if you try to use a 3.21 rear end.

But then again, if you put the transmission in 8th and lean hard on the throttle you will probably improve fuel economy at the expense of very lethargic performance.

But again, IF you are talking about a Ram with a pentastar, I apologize.

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[Ericshere03]

So I may owe you an apology.

I was about to write. " Yes, but still you are talking about a completely different engine with a completely different torque curve". Since normally aspirated engines tend to run most efficiently at their torque peak RPM. (gal per hp per hour)

But then I realized you may be talking about a Ram with a pentastar engine.

If you are talking about a ram with the same engine with the same transmission ratios then you may have a point.

Though I still think that the transmission may just compensate by running around in 7th gear if you try to use a 3.21 rear end.

But then again, if you put the transmission in 8th and lean hard on the throttle you will probably improve fuel economy at the expense of very lethargic performance.

But again, IF you are talking about a Ram with a pentastar, I apologize.

I am talking about a ram Ecodiesel, they have a 3.21 rear gear, 32” tires, same transmission and same engine, larger and heavier but more aerodynamic.

If I were to take my ecodiesel and install 37’s with factory 3.73 gears, my “effective” ratio will be nearly EXACT (well almost 3.23) to the ram above. BFG K02 tires are only 12 lbs heavier than the 32’s.

Aerodynamics and tire weight aside, they two should be equal.

 

[dcmdon]

I am talking about a ram Ecodiesel, they have a 3.21 rear gear, 32” tires, same transmission and same engine, larger and heavier but more aerodynamic.

If I were to take my ecodiesel and install 37’s with factory 3.73 gears, my “effective” ratio will be nearly EXACT (well almost 3.23) to the ram above. BFG K02 tires are only 12 lbs heavier than the 32’s.

Aerodynamics and tire weight aside, they two should be equal.

Ok. well, either way. Now I get it. Same engine, transmission, and gear ratio.

You aren't crazy. Ha. Are you comparing numbers with 4wd ram? or 2wd?

 

[Ericshere03]

Ok. well, either way. Now I get it. Same engine, transmission, and gear ratio.

You aren't crazy. Ha. Are you comparing numbers with 4wd ram? or 2wd?

Either is available with 3.21

 

[Hootbro]

There is a point where trading in on a Prius will make sense. Just enjoy what you have.

 

[Shoebox]

I'm confused as to why this is even being asked. You act as though nobody has run 37s on the diesel. Your mileage will go down. Almost every change you make will decrease your mileage. Just going from stock Rubicon bumper to stubby reduced my mpg by 1-2.

 

[mx5red]

Haven’t plenty of people posted their mileage after putting 37s on?
I don’t pay attention to this but I’m assuming always lower.
Sits higher/aerodynamics, I wonder if the difference in rotational mass makes a difference.. even if tire weighed the same, the bulk of that mass is spread out further from the center.

 

[Ericshere03]

There is a point where trading in on a Prius will make sense. Just enjoy what you have.

I definitely enjoy it, very impressed as a whole, I didn’t want to destroy its most impressive feature, the MPG.

Also, I am trying to justify 37’s when I know 35’s are all I’ll ever need. I’m not rock crawling a 60 thousand dollar vehicle.

I have wanted a diesel Jeep since I was a teenager driving a 4.2 liter YJ, when AEV made the brute, I listed for that too… Now Jeep finally stepped up and made it all happen! It’s not perfect but it a very fine package … is it sick that I still see a JK brute and want one?

 

[Dougstdig]

You are missing one of the most important part of fuel efficiency of which can not be changed on our trucks. If you have an identical powertrain and weight between the Gladiator and Ram the ram will get better mileage because its not a brick in the wind.

Not sure what everyone else is getting, but Saturday driving from Jacksonsonville to Gainesville, FL after getting the bed sprayed…I got the following on an engine with less than 1.000 in the odometer…

 

[Jefe1018]

Not sure what everyone else is getting, but Saturday driving from Jacksonsonville to Gainesville, FL after getting the bed sprayed…I got the following on an engine with less than 1.000 in the odometer…

That’s impressive, but I take it stock 33’s + Florida really helps!

I have 37’s in Nevada, still get 22 highway though!

 

[Dougstdig]

That’s impressive, but I take it stock 33’s + Florida really helps!

I have 37’s in Nevada, still get 22 highway though!

True. I done expect mine will remain in its current form for long. I suspect the 29’s will be a thing of the past for sure…but far better than if it were the 3.6.

 

[Terminus33]

True. I done expect mine will remain in its current form for long. I suspect the 29’s will be a thing of the past for sure…but far better than if it were the 3.6.

35's and 4.11 on the 3.6 the best I get is 20-21 mpg. makes me a bit jealous of the diesel. but that premium for the diesel is just too much for me. and my trips are usually short.

 

[WXman]

The 3.21 gear does seem to be the sweet spot for this powertrain. Traditionally vehicles with gas and diesel options have always come with numerically lower axle ratios if you select the diesel because the power output is totally different and you need to keep RPM in a different range. I was shocked when Jeep used 3.73 with the diesel. The 3.45 from the JL would have been a much better fit.

 

[Gren71]

God I wish the diesel was out when I got my jt

 

[Jefe1018]

God I wish the diesel was out when I got my jt

Im glad I waited, but almost didn’t. I love the truck and everything about it, but that Bosh injection pump and DPF might keep me up at night some day.

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