F350: 4.30 or 3.73 Gears

RCMAN46 wrote:

Denny & Jami wrote:
Well it's obvious that very few here has actually changed gears in a truck and then pulled the same load like I have.

Denny

What transmission did you have on the truck you changed gearing on?

I've been around rving for a long time and built a few trucks to pull with but the one that had a 4 speed standard that I changed to 4.10 from 3.54 was the most noticeable but the C6 built with towing in mind and a RV stall converter was next, it was changed from 3.73 to 4.10 gears. Every other truck I've bought and used for pulling had the right from the start.

Denny

Something else to consider is that you are putting less stress on the transmission torque converter or clutch on every initial start if you have a higher gear reduction in the axles.

Denny & Jami wrote:
Well it's obvious that very few here has actually changed gears in a truck and then pulled the same load like I have.

Denny

What transmission did you have on the truck you changed gearing on?

play with the numbers.. LINK

http://johnmaherracing.com/calculators/gear-ratio-calculator/

MFL wrote:
Learjet... I'm curious as to your tire/wheel size, as you mentioned you'd rather have gotten the 4.30 gears?

I ordered my truck, so could choose which ever gears. I ordered the standard 245/75/17s, to keep my 4x4 a little lower, to keep my FW more level. I stayed with 3.73 gearing, knowing that the smaller tires would make a difference in overall gearing. If I had ordered with the 275/70/18s, I probably would have ordered the 4.30.

Jerry

275/65R18

Well it's obvious that very few here has actually changed gears in a truck and then pulled the same load like I have.

Denny

Denny & Jami wrote:
I've driven a Ford V10 with 3.73 gears and 4.30 gears and all the way through the gears the 4.30 wins hands down, I have friends with 6.7 Fords with 3.54 and 3.73 gears again the lower gears win. One of my Ford trucks with a 460 I changed from 3.73 to 4.10 night and day difference pulling the same load.

The 6 speed makes a dig difference because the second OD keeps the rpm down when cruising down the road in 6th pulling because the final gear ratio puts more available power to the ground.

No what is said the final mechanical advantage (rear gears) makes the difference, just go to any truck specs and see what happens to the towing capacity increases with lower gears.

Denny

The reason the specs go up with lower gears is because of duty cycle. It has nothing to do with gears making power........they don't. The same thing with HP. The reason they derate a 4 or 5 series truck engine is because of duty cycle.

Like I said, if you don't believe me just go dyno your truck and see what happens when dyno'ed in a lower gear. The fact is, a lower gear WILL reduce the power to the ground, not increase it. That is a engineering certainty.

Learjet... I'm curious as to your tire/wheel size, as you mentioned you'd rather have gotten the 4.30 gears?

I ordered my truck, so could choose which ever gears. I ordered the standard 245/75/17s, to keep my 4x4 a little lower, to keep my FW more level. I stayed with 3.73 gearing, knowing that the smaller tires would make a difference in overall gearing. If I had ordered with the 275/70/18s, I probably would have ordered the 4.30.

Jerry

rjstractor wrote:

Denny & Jami wrote:
The rear end gears are the final torque multiplier, so the 4.30 gears will give you more power at the pavement.

Here's a simple explanation, if you have a 10 to 1 torque multiplier on a wench it will take 100 ft lbs of torque to apply 1000 lbs of torque to the bolt but if you use a 5 to 1 it will take 200 lbs of torque to get the same 1000 lbs at the bolt.

So even when using the lower transmision gear you will not get the same torque to the rear wheels when using 3.73 gears over the 4.30 gears.

Yes and no. You're leaving out the fact that the transmission multiplies torque exactly the same way as the rear axle. It makes no difference where the torque is multiplied. If third gear is 1:1 and fourth is .67:1, a 3.73:1 rear axle in third gear has a torque multiplication of 3.73:1. A 4:30 rear axle in fourth gear has a torque multiplication of only 2.88:1.

I agree....but I'm tired of going around and around...its basic physics. But people don't think of it that way...they want to look at just the axle.

its what comes out the engine rpm and goes to the axles rpm...all in between is just gearing. just like a trans axle works. I am referring to all other gears except 1st

a stuck rusty bolt..

a 6 inch long wrench

or

a 12 inch long wrench...

same with different final drive gears.

a 12 inch long wrench will have an easier time turning the rusty bolt..
same with a driveshaft and an axle..