3.21 vs. 3.92 gear ratio - Ram 1500

[clinebarger]

Originally Posted by IndyIan
https://www.ramforumz.com/threads/3-55s-vs-3-92s-with-8-spd.146873/

I'm very surprised to see the top gear ratio is the same on the 6 and 8 speed, seems crazy the 8spd is that much more fuel efficient.
3.92 puts the final drive ratio about the same as my Outback, which pushes much less air but hasn't got a whole lot of torque at 1500rpm either. I think with the 8spd there's not a whole lot of reasons to go with the 3.92 unless you are towing heavy alot. I'm pretty sure my Dad's 2018 6spd has got the 3.21 and unloaded it does 60 mph quite happily in top gear. Its not like the engine sounds terrible if it downshifts either, so I'd rather get good mileage most of the time and then have the odd downshift.


This is a little off topic......The 1500 Ram never actually used a true 6 speed! It's still the same 545RFE with Two 2nd gear ratios. FCA just renamed it 65RFE for marketing reasons as GM & Ford had true 6 speeds. It never uses the 1.50 & 1.67 ratios in succession.

 

[Skippy722]

Originally Posted by clinebarger
Originally Posted by IndyIan
https://www.ramforumz.com/threads/3-55s-vs-3-92s-with-8-spd.146873/

I'm very surprised to see the top gear ratio is the same on the 6 and 8 speed, seems crazy the 8spd is that much more fuel efficient.
3.92 puts the final drive ratio about the same as my Outback, which pushes much less air but hasn't got a whole lot of torque at 1500rpm either. I think with the 8spd there's not a whole lot of reasons to go with the 3.92 unless you are towing heavy alot. I'm pretty sure my Dad's 2018 6spd has got the 3.21 and unloaded it does 60 mph quite happily in top gear. Its not like the engine sounds terrible if it downshifts either, so I'd rather get good mileage most of the time and then have the odd downshift.


This is a little off topic......The 1500 Ram never actually used a true 6 speed! It's still the same 545RFE with Two 2nd gear ratios. FCA just renamed it 65RFE for marketing reasons as GM & Ford had true 6 speeds. It never uses the 1.50 & 1.67 ratios in succession.


I hated that transmission. The jump from 1st to 2nd is entirely too big. Though I believe the 65RFE allowed you to use all 6 forward gears IF you used electronic range select, where the 545RFE would lock out 2nd prime.

 

[samven]

If you are getting taller tires or the 20" rims go with the 3.92. It ends up being the equivalent of the older 17" rims and 3.55. If your not going to haul anything or tow anything why get a pickup truck.

 

[gfh77665]

Originally Posted by xxch4osxx
My Ram has the 3.55 gears and cruises along at 60mph at around 1700rpms. Works for me.


THIS ^^^

I bought my RAM last June. The local dealer did not have my choice with the 3.55 gears, but he found one at a another dealership and traded for it. The 3.55 is the best choice. Far better towing capacity at 7,320 lbs and same MPG as the 3.21's.

 

[clinebarger]

Originally Posted by Skippy722
Originally Posted by clinebarger
Originally Posted by IndyIan
https://www.ramforumz.com/threads/3-55s-vs-3-92s-with-8-spd.146873/

I'm very surprised to see the top gear ratio is the same on the 6 and 8 speed, seems crazy the 8spd is that much more fuel efficient.
3.92 puts the final drive ratio about the same as my Outback, which pushes much less air but hasn't got a whole lot of torque at 1500rpm either. I think with the 8spd there's not a whole lot of reasons to go with the 3.92 unless you are towing heavy alot. I'm pretty sure my Dad's 2018 6spd has got the 3.21 and unloaded it does 60 mph quite happily in top gear. Its not like the engine sounds terrible if it downshifts either, so I'd rather get good mileage most of the time and then have the odd downshift.


This is a little off topic......The 1500 Ram never actually used a true 6 speed! It's still the same 545RFE with Two 2nd gear ratios. FCA just renamed it 65RFE for marketing reasons as GM & Ford had true 6 speeds. It never uses the 1.50 & 1.67 ratios in succession.


I hated that transmission. The jump from 1st to 2nd is entirely too big. Though I believe the 65RFE allowed you to use all 6 forward gears IF you used electronic range select, where the 545RFE would lock out 2nd prime.


It's a .17 difference between the 2, How would you even notice? It's a large 1-2 ratio jump regardless. GM got ridiculed for years over the 4L60E having a 3.06 to 1.63 1-2 ratio jump.

 

[Skippy722]

Originally Posted by clinebarger


It's a .17 difference between the 2, How would you even notice? It's a large 1-2 ratio jump regardless. GM got ridiculed for years over the 4L60E having a 3.06 to 1.63 1-2 ratio jump.


I'm not following, it's almost half? It felt like it would just fall on its face shifting from 1st to 2nd, the spacing of the ZF8 is so much better.

 

[clinebarger]

1.67 to 1.50 isn't much of a difference is what I meant.....Why not use 68RFE ratios which would have been easy enough?? Like they did on the gas powered 5.7L/6.4L 2500 trucks.

 

[DuckRyder]

Looks like electronic locker requires 3.92, so i'd get 3.92.

You can get a no spin in 3.21

 

[supton]

Originally Posted by clinebarger
1.67 to 1.50 isn't much of a difference is what I meant.....Why not use 68RFE ratios which would have been easy enough?? Like they did on the gas powered 5.7L/6.4L 2500 trucks.

I think Skippy is saying 1&2, not 2&3. Looks like 65RFE Is 3/1.67/1.5/1/0.75/0.67 but never uses both 1.67 AND 1.5, unless if using range selector mode. Upshifting from 1.67 to 1.5 would be minor, but upshifting from 1.5 to 1:1 must have been quite noticable.

But not as bad as going from 3:1 to 1.67:1! That's 4L60 territory, as you mention.

I get why GM kept that trans around for a long time but I liked to joke that it was a modern day Powerglide in the trucks. Put it to work and "you were not supposed to use overdrive while towing". 1st was so deep it was only a takeoff gear. That meant it was banging between 2 gears while working. Voila! a Powerglide.

 

[GMBoy]

I have a 2016 Ram Limited with Hemi and 3.21. Runs strong and mpg is very good. Rear axle ratio doesn't make as much as a difference as years past with the 8 speed transmission offering so many ratios.

 

[Snagglefoot]

Originally Posted by GMBoy
I have a 2016 Ram Limited with Hemi and 3.21. Runs strong and mpg is very good. Rear axle ratio doesn't make as much as a difference as years past with the 8 speed transmission offering so many ratios.


Exactly, plus you can electronically set the gear you are towing in.

 

[TheBattman]

A couple of thoughts having just purchased a new 2020 Ram 1500 HEMI... trading a 2017 in similar trim (Big Horn), which followed a 2014 Big Horn with the 5.7:

My 2017 had the 5.7HEMI, 8 speed trans, and the 3.92 gears. My overall mixed MPG was 16mpg average. My 2014 with same engine (but the older transmission), and 3.21 rear end got overall average MPG of 17.5+.

My new 2020 with the 5.7, 8 speed and 3.21 is currently at an overall calculated MPG of close to 18mpg.

I did a little towing with the first two, with trailers as heavy as 6K lbs. PUlled my horse trailer today (unloaded) that weighs about 1500lbs. I can barely tell the difference in towing between the two gear ratios and the 8 speed trans. I'm sure if I were to max out the rated towing capacity, then the 3.92 might be desirable. But this transmission is pretty incredible.

As to raw, unloaded acceleration - while I don't go to a track or do any serious timing of 0-60, the sensation is just slightly different. The 3.92 was easier to break the tires loose on dry pavement.

IF you are considering the small Ecco Diesel... I would strongly encourage you to do some serious research. While most owners are really pleased at purchase, there are some pretty significant issues with that engine that so-far have not really been rectified. While a portion of owners have no major issues - many do.

Either way - good luck on making your decision.

Originally Posted by Snagglefoot
Originally Posted by GMBoy
I have a 2016 Ram Limited with Hemi and 3.21. Runs strong and mpg is very good. Rear axle ratio doesn't make as much as a difference as years past with the 8 speed transmission offering so many ratios.


Exactly, plus you can electronically set the gear you are towing in.

 

[The Critic]

Originally Posted by TheBattman
A couple of thoughts having just purchased a new 2020 Ram 1500 HEMI... trading a 2017 in similar trim (Big Horn), which followed a 2014 Big Horn with the 5.7:

My 2017 had the 5.7HEMI, 8 speed trans, and the 3.92 gears. My overall mixed MPG was 16mpg average. My 2014 with same engine (but the older transmission), and 3.21 rear end got overall average MPG of 17.5+.

My new 2020 with the 5.7, 8 speed and 3.21 is currently at an overall calculated MPG of close to 18mpg.

I did a little towing with the first two, with trailers as heavy as 6K lbs. PUlled my horse trailer today (unloaded) that weighs about 1500lbs. I can barely tell the difference in towing between the two gear ratios and the 8 speed trans. I'm sure if I were to max out the rated towing capacity, then the 3.92 might be desirable. But this transmission is pretty incredible.

As to raw, unloaded acceleration - while I don't go to a track or do any serious timing of 0-60, the sensation is just slightly different. The 3.92 was easier to break the tires loose on dry pavement.

IF you are considering the small Ecco Diesel... I would strongly encourage you to do some serious research. While most owners are really pleased at purchase, there are some pretty significant issues with that engine that so-far have not really been rectified. While a portion of owners have no major issues - many do.

Either way - good luck on making your decision.

Originally Posted by Snagglefoot
Originally Posted by GMBoy
I have a 2016 Ram Limited with Hemi and 3.21. Runs strong and mpg is very good. Rear axle ratio doesn't make as much as a difference as years past with the 8 speed transmission offering so many ratios.


Exactly, plus you can electronically set the gear you are towing in.

This is very helpful - thank you!

 

[The Critic]

I drove trucks with both gear ratios. The 3.21 was a bighorn 2wd while the 3.92 was a 4x4 with off-road tires (built-to-serve edition). The 3.92 was a bit more responsive but the difference was not enough for me to justify the increased fuel costs.

My 3.21 is delivering very good fuel economy so far. A highway run at 65mph today yielded 23mpg per the computer. From my experience with the computer it is about 4% optimistic. Even if it was 10% off, 20mpg+ is very good for a HEMI and I rarely see 3.92 trucks achieving this.

 

[demarpaint]

I'd skip the diesel. With the 8 speed AT I'd take the slight MPG hit and go with the 3.92, and have the extra power if/when I need it. And the electronic lockers are nice if/when you need them.

 

[4WD]

Didn't he buy a truck already ?

 

[Quattro Pete]

I love that instrument cluster!

 

[GMBoy]

Originally Posted by Quattro Pete
I love that instrument cluster!


You should see the Longhorn and Limited clusters! Even better!

 

[The Critic]

Just passed 1200 miles on my Ram with the 3.21 gear ratio. In mixed driving with 89 octane, the computer is showing 18.0 mpg. My manual calculations have found the onboard computer to be about .5 mpg high so I think it is reasonable to say that I am averaging 17-18 mpg.

For my use, I have no regrets about choosing the 3.21 and the fuel economy is very reasonable for an older port-injected V8. The start/stop is definitely helping though. On average, I spend 5-10 min per trip at stoplights and being able to have the engine off has to be helping.

 

[JTK]

Critic, sorry if I missed it, but what factory tires came with your Ram and what do you air them up to?

I'm hand calculating 21mpg average with my 2019 Ram 1500 classic, w/ hemi and 3.21s. My truck has the 17" wheels with GY Wrangler SRAs that I have aired up to ~41psig.