Opinions on 6.4 power for different Rear Gears?

[BSDually]

I'm throwing out a few questions for some thoughts. F350
Same 6.4 motor, same 5-spd Auto, different rear gears!

*Does this mean the engines are under rated or do they work any harder with 4.10 or 4.30 gears?
* Chevy & Dodge use the 3.73 as standard with their engines. Why does Ford offer so many rear combinations?
*I understand the gearing and power and how the engine will work harder and rev up / or tach higher while running/towing. But does this work the engine harder and trans? I would think nothing in the engine or trans. changes to accomodate higher gears?
****These Duallies seem very heavy, pushing 9000 lbs loaded. pulling a 15000 lb trailer only so many times a year, does it justify going to 4.30 gears, when I will want to drive as a everyday truck now and then as well. But with 4.10 gears I will exceed my legal GCWR truck & trailer.****

I need piece of mind knowing that there is a motor/tranny difference between 4.10 or 4.30 otherwise why does Ford not say that a 4.10 and 6.4 can pull 26,000 lbs GCWR too.

*** Does the higher gear # 4.30 make the engine/trans work easier?
If the engine has to run and rev higer in the rpm range. Seems like the engine would be working and straining harder to reach a smooth out period when heavy towing.
Allot of info. Please answer what you can. This advice is very helpful to me and hopefully may help someone else.

Thanks

[SmokeyWren]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: PSF350</div><div class="ubbcode-body">*** Does the higher gear # 4.30 make the engine/trans work easier? </div></div>

Yes. For the same load, the drivetrain has to do less hard work with the 4.30 rear end than with the 4.10. Or you can tow more weight with the 4.30 rear end than with the 4.10 rear end without straining the truck.

Think of the axle ratio as a lever. The bigger the number the longer the lever. It's easier to move the same boulder with a longer lever. So given the same boulder, the longer the lever the easier it is to move that rock. At some point you can't budge the rock without using a longer lever.

In the F-350 DRW, Ford offers you a lever 3.73 or 4.10 or 4.3 feet long. With the 4.10 lever you can move a boulder that weighs 23,500 pounds without busting a gut. But with the longer 4.30 lever, you can move a bigger rock, up to 26,000 pounds.

Ford does an excellent job in determining the GCWR for their pickups. If your gross weight is going to be more than 23,500 pounds, then you're risking busting a gut if you try to get by with a 4.10 lever.

When you grab a longer lever, you still have the same arms and legs and muscles, but you can move a bigger rock without busting a gut. With the F-350 DRW, you still have the same engine and tranny and driveshaft, but with the 4.30 rear axle ratio you can move a bigger trailer without busting something in the truck.

[Deeregreen]

Smoke, that was probably the best description I have seen anywhere for why you use different rear ratio's.

[BSDually]

SmokeyWren, great input. It makes sense that the engine would work less harder with a giant mechanism giving more leverage.

Keep the reply's coming.

Thanks for the feedback.

Bob

[davydee]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: PSF350</div><div class="ubbcode-body">SmokeyWren, great input. It makes sense that the engine would work less harder with a giant mechanism giving more leverage.

Keep the reply's coming.

Thanks for the feedback.

Bob </div></div>

Ditto from me, too! David

[SmokeyWren]

Thanx for the flowers, folks.

So now that you understand why you need a 4.30 rear end for over 23,500 pounds gross combined weight, what happens when you dump the trailer and run around unloaded?

You still have that long lever needed to move that huge rock, but now you just need to move a small rock. You don't need that much leverage to move the small rock, but keep it handy for when we come upon another big boulder. So you're stuck with it - unless you can come up with another overdrive gear to offset the long lever.

That's why they make aftermarket auxiliary transmissions. With a U.S.Gear or Gear Vendors auxiliary tranny, you have another gear to give you 20 percent more overdrive. So using the "double" overdrive gear, your 4.30 rear end "feels like" a 3.44 rear end. Perfect for unloaded cruising, or using the trailer toter for a commuter car. But not cheap. They cost over $3,000. But if you need a heavy duty trailer toter some of the time but a commuter car most of the rest of the time, then an auxiliary tranny may be just the option you need. On a new truck that cost $45,000, the $3,500 cost of a Gear Vendors double overdrive is only 7.8 percent of the total cost of the tow vehicle. Looking at it in that light, that's reasonable. [img]/forums/images/%%GRAEMLIN_URL%%/cool.gif[/img]

[Packard8]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SmokeyWren</div><div class="ubbcode-body"> That's why they make aftermarket auxiliary transmissions. With a U.S.Gear or Gear Vendors auxiliary tranny, you have another gear to give you 20 percent more overdrive. So using the "double" overdrive gear, your 4.30 rear end "feels like" a 3.44 rear end. Perfect for unloaded cruising, or using the trailer toter for a commuter car. But not cheap. They cost over $3,000. But if you need a heavy duty trailer toter some of the time but a commuter car most of the rest of the time, then an auxiliary tranny may be just the option you need. On a new truck that cost $45,000, the $3,500 cost of a Gear Vendors double overdrive is only 7.8 percent of the total cost of the tow vehicle. Looking at it in that light, that's reasonable. [img]/forums/images/%%GRAEMLIN_URL%%/cool.gif[/img] </div></div>

I had a Gear Vendors OD in my old F250 6.9 with a C6 trans and was quite happy with it. However, I've read that it is not well suited for higher gross weight vehicles like an F450 pulling a big 5'er, even when "locked out".

I wonder why a two-speed rear axle isn't offered...seems like well proven tech that is used on medium & HD trucks and it seems that the cost would be less than a Gear Vendors or similar aux trans.....????

[Super Duty John]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: SmokeyWren</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: PSF350</div><div class="ubbcode-body">*** Does the higher gear # 4.30 make the engine/trans work easier? </div></div>

Yes. For the same load, the drivetrain has to do less hard work with the 4.30 rear end than with the 4.10. Or you can tow more weight with the 4.30 rear end than with the 4.10 rear end without straining the truck.

Think of the axle ratio as a lever. The bigger the number the longer the lever. It's easier to move the same boulder with a longer lever. So given the same boulder, the longer the lever the easier it is to move that rock. At some point you can't budge the rock without using a longer lever.

In the F-350 DRW, Ford offers you a lever 3.73 or 4.10 or 4.3 feet long. With the 4.10 lever you can move a boulder that weighs 23,500 pounds without busting a gut. But with the longer 4.30 lever, you can move a bigger rock, up to 26,000 pounds.

Ford does an excellent job in determining the GCWR for their pickups. If your gross weight is going to be more than 23,500 pounds, then you're risking busting a gut if you try to get by with a 4.10 lever.

When you grab a longer lever, you still have the same arms and legs and muscles, but you can move a bigger rock without busting a gut. With the F-350 DRW, you still have the same engine and tranny and driveshaft, but with the 4.30 rear axle ratio you can move a bigger trailer without busting something in the truck.

</div></div>

It's why guys with shorter arms usually beat taller guys in an arm wrestle....

[jayhirsch]

Some real world feedback..I pulled my 16,500 5th wheel over all the passes in Colorado last summer with standard 3.73 gears. Transmission downshifted when necessary...and I had no real problems. On the interstate..I could pull in overdrive at 65 mph , with the cruise on and it rarely needed to shift down. The only place it felt a bit sluggish was pulling away from a dead stop...especially up a hill...but I can live with that. When not towing, I like to cruise at 75-80 and the 3.73's are great for that. My opinion..4.10's and 4.30's are only needed if you are going to pull more than 16.5 lbs...or you are going to go oversize tires..

[BrianF14]

I think litespeed hit the nail on the head. The lower gearing only helps from a dead stop. Once you are moving, the tranny will select the correct gear. At the same speed on flat highway, both the 4.30 and the 3.73 will run in OD, but the 4.30 engine will be running faster, hence worse mpg. Up a hill, the 4.30 may not need to downshift, whereas a 3.73 would downshift to 4th to get the needed power. In other words, the tranny will compensate for the 3.73 rear end. The only time it cannot do this is from a dead stop, since you can't downshift below first. So if you have a 3.73 (which I do), you should do what you can not to stop with a heavy 5er on a uphill so you don't have to get it going from zero.

[torino73]

I run a SRW F350, and plan on ordering a new one this spring. I sure wish I could get a Ford SRW with the 4.10 to offset the 35's I run. I'm not sure about newer Chevys, but I know that in some of the earlier Dmax trucks you could get the 4.10 rear in their 3/4 ton pickup. I know (at least on my '05) that the rear in the dually was a Dana 80, and I think they use a bigger Dana unit on the very low-geared 550's and such- and the SRW's are equipped with a Sterling 10.5. I'm not sure if the Sterling is not compatable with bigger gears, or if Ford has another reason for limiting rear gears on SRW trucks, but I know I don't like it. I have not seen alot of posts on broken Sterlings on this site, but I know that I would be willing to pay extra for the Dana if I could get the gear of my choice. I'm not willing to go with a Dually- I just don't need all that, and my truck is primarily used for hauling wood in off-road conditions. Duallies are just not good for that application, and it's difficult and cost prohibitive to get a decent mud tire for a dually truck.