Rear axle ratios

[hemismith]

I've had a hard time finding a truck with everything I want on it, so I'm debating the need for higher rear axle ratios. Here are the net 1st gear ratios for various half-ton trucks:

Make Rear 1st
Toyota 4.30 14.32
Ford 3.31 13.80
Ford 3.55 14.80
Ford 3.73 15.55
Chevy 3.08 12.41
Chevy 3.42 13.78
Ram 3.55 16.73
Ram 3.92 18.48

The Chevy seems like it definitely ought to have the optional gears.

The Ram is for the 8-speed; the 6-speed definitely needs them but it appears the 8-speed compensates sufficiently, especially since the 2nd gear drop is much less than the others.

The Ford 3.5 only comes with 3.31; does the turbo give it enough torque so it doesn't really need the 3.55s?

Thanks.

[hemismith]

Tachdriver wrote:
I was just on another forum and the 2016 towing spec shows the same towing capacity of the 3.55 as the 3.31.

You're right; it appears that the payload package is what gives it more capacity.

I'm not so much interested in the tow rating though, which is *usually* heavily influenced by the gear ratio, but rather just in how well it pulls. My post was prompted by reports of the Ram 2500 with 6.4 Hemi bogging with the standard gears. When I ran the numbers I saw that the net ratio is relatively low due to the ratios of the transmission (12.05 with a 3.73 rear).

[hemismith]

patriotgrunt wrote:
Ford's 3.5 EB does come with the 3.55 optional rear end. Another key aspect to Ford's rear axle is the ability to electronically lock them. I've used it numerous times and not needed to engage the four wheel drive on soft terrain.

I drove an EB 3.5 today with the max tow package and noticed the differential lock switch; I forgot that a locking differential and 3.55 gears are part of that. I haven't driven one with the 3.31 gears. I've driven a 2.7 but don't remember if it had the 3.55 or 3.73 gears.

[Kalabin]

Before we get too deep in deciding gears how much are you looking to tow with your truck?

[hemismith]

lawnspecialties wrote:
I'm assuming you're only considering gas engines? That's a huge factor in this decision.

Good point. I'm only considering half-tons right now and there's only one diesel, although I think that one could be included as it revs a little higher than most and doesn't have the torque of the HD diesels. Many if not most of the Ecodiesels I see have the optional gears.

[blt2ski]

What are the tire diameters. As that can make a difference too. A 2" diam change is like going from a 3.73 to a 4.10 if you go smaller, or a 4.10 to a 3.73 if you go to a larger tire.

Also torque plays a part in the take off part too. Not so much as HP when moving a road speed. One needs both.

Marty

[Tachdriver]

hemismith wrote:
I've had a hard time finding a truck with everything I want on it, so I'm debating the need for higher rear axle ratios. Here are the net 1st gear ratios for various half-ton trucks:

Make Rear 1st
Toyota 4.30 14.32
Ford 3.31 13.80
Ford 3.55 14.80
Ford 3.73 15.55
Chevy 3.08 12.41
Chevy 3.42 13.78
Ram 3.55 16.73
Ram 3.92 18.48

The Chevy seems like it definitely ought to have the optional gears.

The Ram is for the 8-speed; the 6-speed definitely needs them but it appears the 8-speed compensates sufficiently, especially since the 2nd gear drop is much less than the others.

The Ford 3.5 only comes with 3.31; does the turbo give it enough torque so it doesn't really need the 3.55s?

Thanks.

I was just on another forum and the 2016 towing spec shows the same towing capacity of the 3.55 as the 3.31.

[patriotgrunt]

Ford's 3.5 EB does come with the 3.55 optional rear end. Another key aspect to Ford's rear axle is the ability to electronically lock them. I've used it numerous times and not needed to engage the four wheel drive on soft terrain.

[lawnspecialties]

I'm assuming you're only considering gas engines? That's a huge factor in this decision.

[Hideout17]

Lower rear end gears,higher numerically, will get load moving better and keep it moving at the cost of mpg. Lower gears give you more leverage.