4.10 rear in new Ford F350

Lynnmor wrote:

Me Again wrote:

Lynnmor wrote:

Me Again wrote:
. What you think you gain with the lower diff gears in negated by the steeper OD ratio. Think final gear ratio!

Keep in mind that the transmission is worked harder with higher diff gears.

You multiply the top gear ratio times the diff gear ratio, and the result is always more torque with the lower rear gears. Add to that, each gear change is less of a difference in road speed, keeping the engine at a better RPM.

That basically applies in first gear to get a load moving.

Out on highway one is in 5th and the other in 6th at the same speed. You are dismissing a taller 6th gear od ratio.

I am not dismissing anything, the multiplier (rear gear ratio) is the same in every gear.

So the 4.10 will put 15% more torque to the axle in every gear but it does not put more torque to the rear axle at every speed. So for instance at 60 mph on a 6% grade with 16k lbs in tow and foot to the floor the 6r140 will be in 4th with 3.55 gears and in 5th with 4.10 gears. The 3.55 will be putting 5% more torque to the rear axle. If that trailer is increased to a 22,000 lb 5ver the trucks will be slowed to 50 mph on a 6% grade. Both trucks will be in 4th gear. The 4.10 equipped truck will be running at 2518 rpm and the 3.55 equipped truck at 2180. The 4.10 will be putting 13% more torque to the rear axle. Bottom line is that 4.10s are advantageous for heavier trailers but for a 16k fiver you're better off with 3.55s.

Me Again wrote:

Lynnmor wrote:

Me Again wrote:
. What you think you gain with the lower diff gears in negated by the steeper OD ratio. Think final gear ratio!

Keep in mind that the transmission is worked harder with higher diff gears.

You multiply the top gear ratio times the diff gear ratio, and the result is always more torque with the lower rear gears. Add to that, each gear change is less of a difference in road speed, keeping the engine at a better RPM.

That basically applies in first gear to get a load moving.

Out on highway one is in 5th and the other in 6th at the same speed. You are dismissing a taller 6th gear od ratio.

I am not dismissing anything, the multiplier (rear gear ratio) is the same in every gear.

The new(er) 8 and 10 speed transmissions typically have a lower first gear ratio and the same or a bit higher final overdrive ratio, with more splits in between. Therefore shorter final drive gearing = even more snort down low and through the gears and the same or a bit less rpms in top gear as years past.
Plus we’re not talking diesels here. The thread was about gassers, which benefit even more from this because they have large rpm ranges and “need” more gear reduction to pull bigger loads effectively.
Would anyone complain about having, say, 30 more hp? That’s like complaining about having 4.10s in lieu of 3.73s.

and the new 10 speed trans?

Lynnmor wrote:

Me Again wrote:
. What you think you gain with the lower diff gears in negated by the steeper OD ratio. Think final gear ratio!

Keep in mind that the transmission is worked harder with higher diff gears.

You multiply the top gear ratio times the diff gear ratio, and the result is always more torque with the lower rear gears. Add to that, each gear change is less of a difference in road speed, keeping the engine at a better RPM.

That basically applies in first gear to get a load moving.

Out on highway one is in 5th and the other in 6th at the same speed. You are dismissing a taller 6th gear od ratio. That is why I say the final gear ratio of the 4.10 truck in 6th is similar to the 3.42 in 5th. Both have enough lower gears. The Aisin has a deeper 1st and 2nd gear over the 68RFE. In the 4.10 truck the 1st gear is almost a waste, and some users would like to be able to lock it out. In the 3.42 truck you have a freeway cruiser in 6th, 80 MPH is only 1750 RPM and around 19 MPG.

I would have bought a 3.73 ratio if it was available, however at 60K on the clock and 4 years I am quite happy with 3.42 gears. We did two round trips from the NW to Arizona at 24,500 lbs combined and that combination worked well. We now commute back and forth with a TT at 16K combined.

I owned a truck with 4.10's and .69 OD for 14 years and a freeway cruise is was NOT. It towed fine however. It was gear bound with only 4 forward speeds.

Me Again wrote:

Grit dog wrote:
And now we have the tall gears will out pull the low gears guys checking in.
Regardless of gas/diesel, number of trans gears, apples to apples, lower gears put more power to the ground.
I spose one could cherry pick one particular situation where the trans gears and torque curve of a particular vehicle might favor taller gears, but that will be a very select case.
Or all the mechanical engineers and theory are wrong......
Wonder why trucks with deeper gears generally are rated to tow more??

Back when trucks had 3 and 4 speed tranny's gear ratio really mattered. Now with 6-10 transmission we can look at final gear ratio based on the tranny gear in use.

Example the RAM with 3.42/Aisin in 5th has almost an identical final gear ratio was 4.10 truck in 6th gear.

The 4.10 truck in 6th is work against a .63 OD ratio while the 3.42 truck is in 5th working against a .77 OD ratio.

4.1 x 0.63=2.583
3.42 x 0.77=2.6334

Now add in the shorter tires on the dually with 4.10 and it is a wash. What you think you gain with the lower diff gears in negated by the steeper OD ratio. Think final gear ratio!

When the rear axle ratio changes it effectively changes each gear in the transmission. So with 4.10's each gear is more efficient. It's not just about cruising rpm, it's about efficiency.

Me Again wrote:
. What you think you gain with the lower diff gears in negated by the steeper OD ratio. Think final gear ratio!

Keep in mind that the transmission is worked harder with higher diff gears.

You multiply the top gear ratio times the diff gear ratio, and the result is always more torque with the lower rear gears. Add to that, each gear change is less of a difference in road speed, keeping the engine at a better RPM.

Grit dog wrote:
And now we have the tall gears will out pull the low gears guys checking in.
Regardless of gas/diesel, number of trans gears, apples to apples, lower gears put more power to the ground.
I spose one could cherry pick one particular situation where the trans gears and torque curve of a particular vehicle might favor taller gears, but that will be a very select case.
Or all the mechanical engineers and theory are wrong......
Wonder why trucks with deeper gears generally are rated to tow more??

Back when trucks had 3 and 4 speed tranny's gear ratio really mattered. Now with 6-10 transmission we can look at final gear ratio based on the tranny gear in use.

Example the RAM with 3.42/Aisin in 5th has almost an identical final gear ratio was 4.10 truck in 6th gear.

The 4.10 truck in 6th is work against a .63 OD ratio while the 3.42 truck is in 5th working against a .77 OD ratio.

4.1 x 0.63=2.583
3.42 x 0.77=2.6334

Now add in the shorter tires on the dually with 4.10 and it is a wash. What you think you gain with the lower diff gears in negated by the steeper OD ratio. Think final gear ratio!

Thanks for all this info while researching new truck

And now we have the tall gears will out pull the low gears guys checking in.
Regardless of gas/diesel, number of trans gears, apples to apples, lower gears put more power to the ground.
I spose one could cherry pick one particular situation where the trans gears and torque curve of a particular vehicle might favor taller gears, but that will be a very select case.
Or all the mechanical engineers and theory are wrong......
Wonder why trucks with deeper gears generally are rated to tow more??