Axle ratios and differentials - which to order??

[shamrocksteady]

I am planning on ordering a 4x2 with the V8 and I am struggling to figure out which axle ratio and rear diff to get. I won’t be doing any off-roading, have no plans to tow anything substantial, and will likely just be using the bed for kayaks and bikes. I’m tempted to just save the money and go with the 3.15 axle ratio and non-locking rear differential. Are there any down sides I should be aware of before I pick those options? I’d rather only pay for what I need, but I’d love to hear anyone else’s thoughts before I commit. Thanks!

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[Bryan Simon]

This depends on a couple of things.
hills in your area?
city traffic normal for you?
do you plan on carrying or towing frequently—light or moderate?

I am rural and generally not so hilly.
My commute is unencumbered by city traffic
I do not regularly tow or carry heavy loads
( but I still needed a 4x4 for my sandy area)
I chose the standard 3.31 for rural and freeway cruising.

if predominately city traffic, 3.55 or 3.73 would be a better choice
if carrying or towing regularly, the deeper rear is beneficial.

Raleigh is not all that a flat area and the tall gearing will have an adverse effect on mileage. Towing or carrying a moderate load, the truck really won’t like that tall 3.15 gearing, particularly off the freeway in town traffic.

Im not saying the truck won’t do it, because it will.
Im not saying mine will never be taxed beyond the rated uses, because it will.
just not on a regular basis ( I have an older truck for the heavy dirty work)

Anything other than consistent freeway flying, 3.15, in my opinion is too tall.

 

[notabot]

Old school rationale: If you're into occasional enthusiastic driving and/or every now and then leave the line like you were shot out of a cannon (just because you can), get the 3.73 or taller.

New fangled stuff: AFAIK, the 10spd makes the final gearing so close the only real advantage in a taller or shorter final gear is in 1-2-3 shifts. I've seen the gearing charts but don't remember exactly what I saw.

 

[notabot]

This depends on a couple of things.
hills in your area?
city traffic normal for you?
do you plan on carrying or towing frequently—light or moderate?

I am rural and generally not so hilly.
My commute is unencumbered by city traffic
I do not regularly tow or carry heavy loads
( but I still needed a 4x4 for my sandy area)
I chose the standard 3.31 for rural and freeway cruising.

if predominately city traffic, 3.55 or 3.73 would be a better choice
if carrying or towing regularly, the deeper rear is beneficial.

Raleigh is not all that a flat area and the tall gearing will have an adverse effect on mileage. Towing or carrying a moderate load, the truck really won’t like that tall 3.15 gearing, particularly off the freeway in town traffic.

Im not saying the truck won’t do it, because it will.
Im not saying mine will never be taxed beyond the rated uses, because it will.
just not on a regular basis ( I have an older truck for the heavy dirty work)

Anything other than consistent freeway flying, 3.15, in my opinion is too tall.

Well said!

 

[Mtnman1]

I am planning on ordering a 4x2 with the V8 and I am struggling to figure out which axle ratio and rear diff to get. I won’t be doing any off-roading, have no plans to tow anything substantial, and will likely just be using the bed for kayaks and bikes. I’m tempted to just save the money and go with the 3.15 axle ratio and non-locking rear differential. Are there any down sides I should be aware of before I pick those options? I’d rather only pay for what I need, but I’d love to hear anyone else’s thoughts before I commit. Thanks!

If 4x2, I would go with the locker, especially if you get snow.

Will still help you get out of mudd or wet grass. Getting stuck sucks

 

[IzzysAuto]

For your use I would go with whatever you could get the best deal on. Based upon what you stated.

 

[Buyer2021]

A tall (numerically low) ratio seems perfectly suitable (and fuel-economical) for your described use, but as suggested above I'd not forfeit an otherwise desirable deal chasing a fractionally taller ratio.

Over the 17 years I've owned my 4x2 Supercab, the times I've been thankful for its limited-slip differential is on wet grass and firm but slick soil, especially when the truck is relatively lightly loaded. Examples are unimproved parking areas at many large festival-type events or recreational sites. I've been in situations where adjacent open-differential trucks were not able to start moving at all so needed a tow to ground with traction for both wheels.

If you anticipate encountering those situations then the current limited-slip / traction-lok alternative (e.g. e-locker) may prove worthwhile. Personally I've learned I would not do without that option no matter what the ratio.

Just for your consideration, YMMV.

 

[MJ Heat]

I have a 2019 RCLB with the V8 & 3.15 rear end. It gets about 26 mpg if I drive like I have good sense. By the way, I live nor far from RALEIGH. It is perfect for highway miles.

 

[Calson]

The 10-speed transmission has overdrive gears for 8th, 9th, and 10th gears so going to taller gearing as with 3.55 or 3.73 axle is not going to make an appreciable differnce in the engine RPMs on the highway. My truck with the 3.55 gears has engine RPMs of less than 1500 most of the time on the freeway.

 

[tony72cutlass's']

I got the 3.73 so that I could have the 9.75 rear end. I am averaging 20mpg mixed highway and around town. V8 with 4x4 and rear locker for snow service.

I tend to overthink stuff so I figured for the same price (500$ upgrade to get the e-locker in my area), I may as well get a beefier diff.

That being said, get what you like and you won’t regret it!

 

[SilverPigeon]

I've put these stats elsewhere, but worth repeating on this thread. I chose the Max tow mainly for the 3.73, max low-end torque and acceptable highway rpm:
Gear ratios:

1	4.696
2	2.985
3	2.146
4	1.769
5	1.520
6	1.275
7	1.000
8	0.854
9	0.689
10	0.636

Final drive ratio: 3.73
Tyre Size: 275/60R20 OWL all-terrain
Distance in km for 1 wheel rotation: (838mm x pi)/1,000,000 = .00263265km
Wheel rotations in 110km = 110/.00263265 = 41,782.92
Wheel rotations at 110km/h for 1 min = 41,782.92/60 = 696.38
Driveshaft RPM = 696.38 x 3.73 = 2,597.50
Engine RPM in 10th gear = 2597.50 x .636 = 1652.01 RPM

 

[amschind]

I would look hard at a smaller truck. See if you can fit what you want into the bed of a Maverick or Ranger: you aren't considering a 1 ton Superduty and cost is a factor, so maybe see if you can't meet your needs with a smaller vehicle (and look hard to fuel economy, as thats a big part of total cost of ownership).

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