3.31 gears at 40,000 lbs gross.

ShinerBock wrote:

dodge guy wrote:


Ughh! Spinning 4.30’s is easier all around compared to spinning 3.30’s. It’s basically the same as removing 4K lbs of weight from the vehicle!

Yes, as if the force my legs need to put on the pedals of my 8-speed(which changes the ratio to the tire) bike in short gear is the same as taller gear and it would have no effect on the friction material if there was a clutch on my pedals rather than a chain.

What if you look at it this way: If I have 4.30 gears and I’m pulling a trailer that puts me at 28500 lbs gvw and say I’m travelling 65 mph and let’s assume the power required to do this is 150 hp I will be in 10 th gear running at 1800 rpm and my Powerstroke will be feeding 438 lbft of torque into my torque converter. Now I come to a hill ... say a 6 percent grade. The power require to maintain 65 mph goes to 446 hp. My foot goes to the floor and transmission drops two gears to 8th gear. Now my Powerstroke is feeding 968 lbft of torque into my transmission through my overdrive clutches.


With 3.31 gears say I only lock out 10 gear and I’m towing that same trailer at 65 mph. Now my Powerstroke is turning 1506 rpm and I’m feeding 523 lbft of torque into the transmission on level ground (and if I was concerned about my overdrive gears I could lock out 9) When I hit the hill and my foot goes to the floor I drop to 7 seventh and my overdrive clutches are out of the equation.

You’re not going to come up with a more realistic scenario where an RVer with 3.31 gears is going to be putting more than 968 lbft of torque through the over drive gears.

I'm gettin confused....now I need a show of hands...
Whos team 4x and whos team Shiner?
Lets go boys!

RoyJ wrote:
Wow, physics, hell I'll play :D

For any rigid shaft, torque in = torque out, correct? Basic Physics 101. Unless the shaft deforms, which is a failure...

3.31, 4.30, 4.88 truck, whatever, your max T-input at transmission is always your engine max torque, right? Assuming locked converter.

You axle torque is always dictated by your speed, grade, weight, aero, and instant acceleration. Doesn't matter if you have 3.31/4.30/3.55/4.88/5.13 gears. To pull a 40,000 gvw rig hp 7% grade with no wind at constant speed, you need a FIXED amount of axle torque (thrust), correct?

That means the ONLY difference in stress between a 3.31 and 4.30 truck is the transmission output torque, or driveshaft torque (again, T-in must = T-out). Because on the same hill, a 4.30 truck may be in 6th and the 3.31 truck in 5th.

If you're burning OD clutches, either you've gone above the GVW rating of the tranny, and /or you should've locked out OD.

Again, I don't know anybody pulling a heavy trailer that does WOT Launches. OEMs do extensive testing, including WOT runs on a dyno.

How I figure ring and pinion gears to use in my rig:
1) Find data on where the rig's peak torque is/at what RPM said peak torque reads.
2) Replicate that RPM when I change to larger tires (I'm an off roader/backcountry/boondocking camper :B).
3) If fuel economy be damned; I go one gear higher, numerically, to get more torque in lower RPM range.

Example: I just re-geared the 1ton rear dually axle in my '94 Bronco to 5.13, from 4.10, while running on HMMWV tires (37").

I could have gone with 4.56 or 4.88, but decided I wanted torque ASAP/in the lower RPM range.


My Bronco is no longer a coast to coast rig.

Its' travel radius is about 200 miles, with as much as 200 miles of off-the-road driving/traveling.


MY POST'S POINT: Gears that will put your rig in the engine's torque sweet spot (peak torque).

When I ordered a '99.5 F-350; I noticed that Ford put the PS's peak torque (about 1,800RPMs) at 55MPH in OD.

After a couple slow days, fishin is GOOD for 4x with this thread!

dodge guy wrote:


Ughh! Spinning 4.30’s is easier all around compared to spinning 3.30’s. It’s basically the same as removing 4K lbs of weight from the vehicle!

Yes, as if the force my legs need to put on the pedals of my 8-speed(which changes the ratio to the tire) bike in short gear is the same as taller gear and it would have no effect on the friction material if there was a clutch on my pedals rather than a chain.

^^^^^ You’re sounding kinda like Shiner. You’re making a claim without any kind of logical explanation. If you’re pulling a heavy trailer out of a bog in 1st gear with the transfer case in 4 low and worried about u joints .... yes the 4.30 gears will be less likely to break a u joint than 3.31. Although if the trailer doesn’t come and your tires don’t spin the strain on the joint will be the same in both cases.

Edit: What do you mean by saying "spinning 4.30s is "easier" than spinning 3.31s"
Easier on fuel?
Easier to get the trailer moving from a stop in first gear?
Easier on over drive clutches pulling a heavy trailer up a hill at 60 mph?
Easier on the torque converter at 65 mph with a trailer in tow?

What do you men by easier and under what circumstance is this going to come into play?

RoyJ wrote:
Wow, physics, hell I'll play :D

For any rigid shaft, torque in = torque out, correct? Basic Physics 101. Unless the shaft deforms, which is a failure...

3.31, 4.30, 4.88 truck, whatever, your max T-input at transmission is always your engine max torque, right? Assuming locked converter.

You axle torque is always dictated by your speed, grade, weight, aero, and instant acceleration. Doesn't matter if you have 3.31/4.30/3.55/4.88/5.13 gears. To pull a 40,000 gvw rig hp 7% grade with no wind at constant speed, you need a FIXED amount of axle torque (thrust), correct?

That means the ONLY difference in stress between a 3.31 and 4.30 truck is the transmission output torque, or driveshaft torque (again, T-in must = T-out). Because on the same hill, a 4.30 truck may be in 6th and the 3.31 truck in 5th.

If you're burning OD clutches, either you've gone above the GVW rating of the tranny, and /or you should've locked out OD.

Ughh! Spinning 4.30’s is easier all around compared to spinning 3.30’s. It’s basically the same as removing 4K lbs of weight from the vehicle!

RoyJ wrote:
Wow, physics, hell I'll play :D

For any rigid shaft, torque in = torque out, correct? Basic Physics 101. Unless the shaft deforms, which is a failure...

3.31, 4.30, 4.88 truck, whatever, your max T-input at transmission is always your engine max torque, right? Assuming locked converter.

You axle torque is always dictated by your speed, grade, weight, aero, and instant acceleration. Doesn't matter if you have 3.31/4.30/3.55/4.88/5.13 gears. To pull a 40,000 gvw rig hp 7% grade with no wind at constant speed, you need a FIXED amount of axle torque (thrust), correct?

That means the ONLY difference in stress between a 3.31 and 4.30 truck is the transmission output torque, or driveshaft torque (again, T-in must = T-out). Because on the same hill, a 4.30 truck may be in 6th and the 3.31 truck in 5th.

If you're burning OD clutches, either you've gone above the GVW rating of the tranny, and /or you should've locked out OD.

Thanks Roy:)

Wow, physics, hell I'll play :D

For any rigid shaft, torque in = torque out, correct? Basic Physics 101. Unless the shaft deforms, which is a failure...

3.31, 4.30, 4.88 truck, whatever, your max T-input at transmission is always your engine max torque, right? Assuming locked converter.

You axle torque is always dictated by your speed, grade, weight, aero, and instant acceleration. Doesn't matter if you have 3.31/4.30/3.55/4.88/5.13 gears. To pull a 40,000 gvw rig hp 7% grade with no wind at constant speed, you need a FIXED amount of axle torque (thrust), correct?

That means the ONLY difference in stress between a 3.31 and 4.30 truck is the transmission output torque, or driveshaft torque (again, T-in must = T-out). Because on the same hill, a 4.30 truck may be in 6th and the 3.31 truck in 5th.

If you're burning OD clutches, either you've gone above the GVW rating of the tranny, and /or you should've locked out OD.