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Questions for Ecodiesel owners

Ninety-9 SE-L

Well-Known Member
Apr 23, 2021
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I'm new to the Ram and EcoDiesel (about to buy). I'm trying to understand why everyone here is obsessed with the 3.92 v. 3.21 when we talk about cruising speeds.....

Below is an approximation of the final gearing ratios (red 3.92, Blue 3.21), based on the 'Engineer's Ultimate Guide' thread....and by the way, THIS Engineer has some disagreements with some info in that thread.

The 3.92's full range is 0-23.8MPH, the 3.21's full range is 0-29.8MPH (on factory tires). Right up until the 2.92 has to shift into 2nd gear (dropping it down to 12.31:1), the 3.92 has the torque advantage.

For the record, between 23.8 and 29.8mph, the 3.21 has the torque advantage (15.12 v. 12.31), and it technically keeps switching, but the bottom line is that the 3.92 will accelerate faster...particularly under 23.8mph at full throttle.

With or without a trailer, you're basically looking at the same exact truck after 23.8mph, with the 3.21 FD having just a little more reach at the top end. The 3.21 will have to drop a gear down to reach about the same final G/R as the 3.92, but otherwise you'll be at the same RPM, delivering the same amount of torque/power at the wheels. If you want the 3.21 to drive EXACTLY like the 3.92 at 75mph, just lock it out of 8th....or better yet, don't lock it out of 8th and let the computer decide, then you still have the advantage of that lower gear ratio.

The EcoDiesel reaches peak torque at 1600rpm...fun fact, that's 71mph at 2:15:1 final drive on factory tires.

The 3.92 shines in stop+go traffic, when you have to keep accelerating from 0-24mph, or when you have to climb hills under 24mph.
Again, even on highway grades, the 3.92 won't give you any advantage, unless you're under 24mph, and technically, the 3.21 will give you the advantage from 24-30mph.

Having driven a 2020 Hemi Classic, the only thing I can say for sure is that the transmission is touchy, especially above 6th gear. Move your foot in the slightest, and the trans is just ITCHING to drop a gear or 3. It takes a lot of pedal discipline to prevent that from happening. I've joked many times about the Pedal commander being a ******** accessory that does nothing more than save you from yourself, but in the case of the 8-speed Ram, I can see there being a case for that product to help 'numb' the accelerator pedal on the highway and keep the transmission from dropping down.

I'm curious if there's a product that gives me more control of the transmission, because I really don't see why you couldn't sit in 8th gear for very mild acceleration or headwind. You're not exactly bogging down the 480ftlbs or torque the EcoDiesel is able to put out at 71mph.


Feb 10, 2022
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Good looking rig! Do you have a level or is that stock rebel height?

Dealer quoted me 5 to 6 months, would have been quicker if I wanted a hemi.
My dealer quoted 6 months as well - I ordered 2/7 and it's currently on a train to TN.


Active Member
Oct 28, 2021
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Great choice!

How do you like that bike rack set up? We have some camping trips planned and tried the bikes on the back of camper last year; didn't work. Then I moved them in the bed but that really limits ability to haul anything else.

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