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3.21 vs 3.92: The Last Word

nc_beagle said:
My 2013 Mazda shows my rolling average fuel economy but it also shows a rolling average MPH, which is kind of handy for seeing if I'm trending towards more city driving versus highway. When I first got the car we took it on longer trips and I think my average speed was about 35mph. Now its like 31-32mph on average and my mileage is down a little bit. Would be a handy feature to have on the truck and pretty simple to add to the system.
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All of my Silverado’s had this. I do a lot of freeway driving so my average speed for all driving was always right around 52 mph over many years and multiple trucks. Didn’t change more than 1-2 mph. Most of my driving is at 80-82 mph.

That’s the only reason I went with 3.21’s.
 
J-Cooz said:
Everybody takes this so personal.

My ecodiesel has 3.92s and gets 28+ MPG easily on the highway. I generally drive around 70mph, not much faster. If I lived in the USA where speed limits are 75+ (it's 62mph or 100kmh) in most of Ontario Canada, I'd probably get the 3.21.

Ideally the old 3.55 rear end would probably be ideal.

I do tow and I like the 3.92 combined with the ecodiesels torque. It gets heavy loads moving with very little effort.



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3.55 might be a good compromise for a Hemi. But, the ED has so much low end torque, I really can't see it needing anything shorter than the 3.21. The ED has WAY more than enough grunt from a stop to get anything it's even close to rated to tow moving.

But, if you're going to drive one of those weak-*** Hemis, then I guess you might need a 3.92 to get a really heavy trailer moving reliably.
 
  • Haha
Reactions: c3k
Seems like everybody forgot about the good ole’ days of big lifts, big tires and anemic barely 200 hp motors driving mega highway gears. Everybody thought they had real trucks back then too.😆

Any motor pushing 400 hp these days will do just fine with either gear.
 
Everybody wants to talk about towing and that means torque, not power. I bet even those old 200 HP motors had more torque than a 5.7 Hemi.

Regardless, if you only have barely over 400 ft-lbs, I can see why you would feel a need for 3.92 gears.

Get an EcoDiesel with a GDE tune and you will have more power and more torque than the legendary Ford 7.3L PowerStroke. And you will be just fine with a 3.21 pulling half-ton truck loads.
 
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StuartV said:
Everybody wants to talk about towing and that means torque, not power. I bet even those old 200 HP motors had more torque than a 5.7 Hemi.

Regardless, if you only have barely over 400 ft-lbs, I can see why you would feel a need for 3.92 gears.

Get an EcoDiesel with a GDE tune and you will have more power and more torque than the legendary Ford 7.3L PowerStroke. And you will be just fine with a 3.21 pulling half-ton truck loads.
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Nope.

Used 1990 Dodge RAM 150 LE Extended Cab Specs & Features​

More about the 1990 RAM 150
Buy In-StoreBuy Online
More about the 1990 RAM 150
Buy In-StoreBuy Online
Overview
OverviewMost Popular
LE 2dr Extended Cab SB
5.2L 8cyl naturally aspired 4M
Buy In-StoreBuy Online
Engine TypeGas
Transmission4-speed manual
Drive TypeRear wheel drive
CylindersV8
Fuel & MPG
Fuel & MPG
Fuel typeRegular unleaded
EPA city/highway MPG12/17 MPG
EPA combined MPG14 MPG
Range in miles (city/hwy)360.0/510.0 mi.
Fuel tank capacity30.0 gal.
Engine
Engine
Base engine size5.2 L
CylindersV8
Base engine typeGas
Horsepower170 hp @ 4,000 rpm
Torque260 lb-ft @ 2,500 rpm
Towing & Hauling
Towing & Hauling
Max Towing Capacity4,500 lbs.
Max Payload Capacity1,880.0 lbs.
Drivetrain
Drivetrain
Transmission4-speed manual
Drive typeRear wheel drive
 
Idahoktm said:
Nope.

Used 1990 Dodge RAM 150 LE Extended Cab Specs & Features​

More about the 1990 RAM 150
Buy In-StoreBuy Online
More about the 1990 RAM 150
Buy In-StoreBuy Online
Overview
OverviewMost Popular
LE 2dr Extended Cab SB
5.2L 8cyl naturally aspired 4M
Buy In-StoreBuy Online
Engine TypeGas
Transmission4-speed manual
Drive TypeRear wheel drive
CylindersV8
Fuel & MPG
Fuel & MPG
Fuel typeRegular unleaded
EPA city/highway MPG12/17 MPG
EPA combined MPG14 MPG
Range in miles (city/hwy)360.0/510.0 mi.
Fuel tank capacity30.0 gal.
Engine
Engine
Base engine size5.2 L
CylindersV8
Base engine typeGas
Horsepower170 hp @ 4,000 rpm
Torque260 lb-ft @ 2,500 rpm
Towing & Hauling
Towing & Hauling
Max Towing Capacity4,500 lbs.
Max Payload Capacity1,880.0 lbs.
Drivetrain
Drivetrain
Transmission4-speed manual
Drive typeRear wheel drive
Click to expand...

I mistakenly assumed we were talking about old diesels. Definitely my bad. I knew the old gas motors did not have as much torque as a current Hemi.
 
StuartV said:
I mistakenly assumed we were talking about old diesels. Definitely my bad. I knew the old gas motors did not have as much torque as a current Hemi.
Click to expand...

This is the post that I thought you were referencing.
Dewey said:
Seems like everybody forgot about the good ole’ days of big lifts, big tires and anemic barely 200 hp motors driving mega highway gears. Everybody thought they had real trucks back then too.😆

Any motor pushing 400 hp these days will do just fine with either gear.
Click to expand...
 
Idahoktm said:
This is the post that I thought you were referencing.
Click to expand...

I was. "Everybody thought they had real trucks" (and my earlier reference to the 7.3 PowerStroke) just had me thinking that that post was talking about diesels (which were notoriously weak on power - from the factory). Like I said, totally my bad.
 
I test drove one of the very last F250s with a 7.3 Powerstroke, back in 2003. I remember that they were really touting that it had (IIRC) 250 HP and 525 ft-lbs of torque.

The current ED has more HP (260) and somewhat close amount of torque (480). With an EPA-compliant tune from GDE, the ED will have 305 HP and 565 ft-lbs. More power and more torque than a 7.3 PowerStroke. Pretty impressive, to me. I think that is about the same or slightly more than the Ford 6.0 PowerStroke that replaced the 7.3. I had 3 of those over the years and they really kinda sucked. I think the stock ED is a LOT nicer to drive.
 
Idahoktm said:
Does he call them airplane gears because of how slow jet engines spool up?
Click to expand...

I'm really not sure. First time I heard him use that term was when I bought a '93 Z28 back in my college days and we found out it had something like a 2.73 axle ratio. It was unbelievable that they would put that axle ratio behind a 4 speed in a performance car.
 
WXman said:
I'm really not sure. First time I heard him use that term was when I bought a '93 Z28 back in my college days and we found out it had something like a 2.73 axle ratio. It was unbelievable that they would put that axle ratio behind a 4 speed in a performance car.
Click to expand...
I had a Cutlass in the late 70’s that had a 2.29 axle ratio. That’s crazy but fitting for the 70’s. Dropped a big block in and snapped the axles and blew the gears up within days. Good times.😆
 
Idahoktm said:
What do you have to turn off? On my Tundra, I had to press and hold the nanny button for 5 seconds, but it was just a single tire fire. :LOL:
Click to expand...
Just turn off traction control and let her eat. That asphalt is pretty slick. Probably coulda went for another 50 yards if I had 3.92’s😆
 
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