MPG effect of 3.92 rear end

[RAM 5 times]

I average about 8000 miles a year. When I traded in my 2016 Ram it only had about 16,000 miles on it

when i was still working i would take turns with my wife's jeep and my truck and averaged about 7,500 per year on it. now a little over 4,000. when my truck comes in i'm planning a trip to go see the pittsburgh pirates baseball stadium. used to go to the old stadium back in the early 90's. i'm in southern new jersey so a good 6 hour trip. i'm looking forward to driving the new truck.

 

[John813]

I was stuck between the two. Week days 31 out of 35 miles are highway, mostly uninterrupted flow.

Found a truck with the options I wanted(minus one, shown below) and it had 3.21 gears. At 80-83mph it'll get 20-22mpg with no mds. Think it actually hurts fwiw.

Been debating on adding 3.92s to the bucket list when I go for an anti slip diff.

Didn't buy this truck for MPG, but at the same time I do like going long distances without having to stop for gas every ~250 miles like in the old truck.

 

[firecadet613]

I put 58,000 miles on my 2016 F150 crewcab 4x4, 2.7 EcoBoost that I ordered with 3.55s, in two years. Lifetime mpg average of 17.8mpg with that truck. I have a lead foot and drive about 8-9 over on the highway.

Ordered my 2019 with 3.21s to help with mpg. I drove a 3.21 and 3.92 back to back and it wasn't a big difference. IIRC, final drive ratio of the 3.92 in 8th gear is equal to the 3.21 in 7th gear.

Reading all of this thread and others has made me second guess not getting the 3.92s but either way it's a slower truck than my F150. With 1800 miles I'm at 15.2mpg but it's going up.

I'm expecting better than my F150 once its broken in. I only tow my 8,000lb boat and really haven't done that with the Ram yet.

About to take a 1,000 mile trip so we'll see how she does.

 

[Jus Cruisin]

I went with 3.21's and I tow a 24' enclosed car trailer. I've got 3.55's in my F150 Ecoboost. The Ford has a 6 speed transmission. I don't care what rearend is in the Rams, they'll be kind of pokey compared to half the vehicles on the road. I'm not the least bit concerned.

This is the trailer.... Along with my current truck.

 

[NortherLee]

I do 99.9% city driving and I have the 3.92 on my 2019 Ram. My MPG is approx 13.5mpg right now but I am only at 220 miles so the engine isn't even broken in yet.

I've got the 3.21 axle ratio. At 240 miles I was getting 15.1 MPG on a trip up to Mt. Rainier going from 250 ft. elevation to a mile high and back. At 700 miles: completed a similar trip up Mt. Rainier and overall mileage for the full 700 miles improved to 17.2 MPG. This is on a 2019 Laramie, 5'7" bed, 20" wheels, 4x4, 5.7 hemi. MPG was what was indicated on the dash panel. Acceleration is better than expected but I typically drive with adaptive cruise control (ACC) active.

 

[RAM 5 times]

I went with 3.21's and I tow a 24' enclosed car trailer. I've got 3.55's in my F150 Ecoboost. The Ford has a 6 speed transmission. I don't care what rearend is in the Rams, they'll be kind of pokey compared to half the vehicles on the road. I'm not the least bit concerned.

This is the trailer.... Along with my current truck. View attachment 1348

see a truck doesn't have to be a ram to look good. ( even though they do look better! )

 

[MALO]

I live in Northern VA and commute about 30 miles into work 3 days a week in a fair amount of stop and go. My truck has a 3.92 Axle and for the first 1300 miles I’m averaging around 17.5 which I am quite pleased with.

Mine is getting 12.7 mpg I hope it gets to atleast 15 mpg ... it only has 300 miles on ot

 

[tonyplants]

First time trailering my 7x12 aluminum single axle open trailer (~1000#) with Honda Pioneer 1000-5LE (~1800#). Mainly highway between 65 and 70mph. Pulled smoother than my 2014 Silverado. Real test will be 25' aluminum enclosed with three long tracks in trailer and a fourth shoved in bed.

 

[th3duke]

First time trailering my 7x12 aluminum single axle open trailer (~1000#) with Honda Pioneer 1000-5LE (~1800#). Mainly highway between 65 and 70mph. Pulled smoother than my 2014 Silverado. Real test will be 25' aluminum enclosed with three long tracks in trailer and a fourth shoved in bed.

I really like the 3.92. You definitely can't go wrong with the 3.92 if you're towing - the extra 3000# of towing capability makes it a no brainer IMO. I had a 2017 Sierra and really love the way this pulls compared to my GMC as well - it just feels peppier and better planted.

 

[meltedcheez]

I average about 8000 miles a year. When I traded in my 2016 Ram it only had about 16,000 miles on it

Yikes! I put 8,000 on it in the first four months. I do a lot of driving for work but I also haven't said no to any out-of-town weekend trips. ;-)

 

[Smashy71]

I just went over 3k miles on my rebel. I’m averaging 15.3. When I drove it loaded down with a 20ft trailer hauling a 97 Tahoe amongst other stuff in the bed I weighed easily 12,000 pounds including the ram and got 9.8 total from start to finish 1800 miles. Albeit some tanks were only at 7.5 and 8.5ish because of the mountain passes through Wyoming and Montana. My average speed was 70 and 60 through the passes the truck pulled very strong.

 

[Reduxalicious]

So before I had this Rebel I had a FX2 F150 Tremor


2 door truck, 3.5 1st Gen EcoBoost with a 4.10 rear end, it was a fun truck, this was my average MPG at well you can see



That truck hovered between 16.8 and 15.9 depending on if I was in a headwind and doing 80,.

Enter the rebel



The truck is considerably heavier or being 4wd with a 5.7L N/A V8

Here's my average so far



Now that was actually a week ago, and my average is actually around 15.8 and slowly climbing, my mds is actually kicking in at 70 MPH even

60 vs 60 this truck actually gets better MPG

Over all considering the larger engine and weight difference and the 30+ more HP (Rebel) between these two trucks I really can't complain about Fuel

 

[lasstss]

I would think that if you have 3:92' in the diff, Chrysler would have a corresponding higher 7 or 8th gearing on the trans to make up for it on the highway. Not sure this is the case though. otherwise the 60-70 mph rpms would be a good bit higher.

 

[alacombe]

Mine is getting 12.7 mpg I hope it gets to atleast 15 mpg ... it only has 300 miles on ot

I'm at 2,800 miles at 12.1mpg with the 3.92

 

[Smashy71]

I'm at 2,800 miles at 12.1mpg with the 3.92

Mine did pretty much the same. My first two tanks were 12-13 mpg not I’m a constant 15-18

 

[dutchman187]

I'm at around 1,200 miles and sitting at around 11 average. Mainly in town and a lot of stop signs. I do drive very conservative though. When I take a highway drive it shoots up to 16-18. Still expecting some improvement as I get more miles.

 

[Horkn]

Is that the case, or do the gear ratios in the transmission stay the same regardless of the axle ratio? If they did alter the transmission depending on the axles, that would make up the difference between 8 and 10 speeds that the competition has.

 

[ExcursionDiesel]

I was stuck between the two. Week days 31 out of 35 miles are highway, mostly uninterrupted flow.

Found a truck with the options I wanted(minus one, shown below) and it had 3.21 gears. At 80-83mph it'll get 20-22mpg with no mds. Think it actually hurts fwiw.

Been debating on adding 3.92s to the bucket list when I go for an anti slip diff.

Didn't buy this truck for MPG, but at the same time I do like going long distances without having to stop for gas every ~250 miles like in the old truck.

You'd be lucky to get 16 mpg at 80 with the 3.92. Your getting 20+ mpg. That's a 25% improvement over the 3.92. People that say there is little difference aren't driving on interstates or aren't watching their economy closely. With the 3.92, there is a significant difference with higher speed driving. Economy decreases over 63 mph based on my observations driving on flat ground.

 

[fastarget]

I agree with the above. Anyone know which gears were used to determine ave consumption? Different models with different gears cant have the same consumption as per window stickers.

 

[troutspinner]

You'd be lucky to get 16 mpg at 80 with the 3.92. Your getting 20+ mpg. That's a 25% improvement over the 3.92. People that say there is little difference aren't driving on interstates or aren't watching their economy closely. With the 3.92, there is a significant difference with higher speed driving. Economy decreases over 63 mph based on my observations driving on flat ground.

I definitely agree with this. Most people who purposely build / buy their trucks with 3.92s, do not care or pay attention to gas mileage, they purposely get those gears for other reasons, be it heavy towing, get up and go or to compensate for larger tires.

Personally, I buy trucks equipped with higher gears because at one time I towed heavy and like to put larger tires on my trucks. While I do not tow those weights anymore, I want to maintain that capability and to be quite honest, test driving trucks with 3.21 you can definitely feel the difference and prefer 3.92s.