Differential swap

Ivylog wrote:
Why does a tranny have gears... It's to change the gear ratios. Manually gear down and keep the RPMs up... Same going down the pass.

X2

Changing gears will not increase your horsepower period.

What is so important in pulling hills in 5 th gear with a 4+ rear gear when you can do the same with a 3.xx gear in 4 th gear?

SLE wrote:
Couple things I missed in my post; The Superduty Dana axles can for sure accept ring and pinion upgrades up to a 4.88 without an axle swap, not sure about anything higher as I didn't have the need to research it. Not quite sure what your trying to accomplish with your comparison of the 5.3 with 3.73s, that's apples and oranges. Swapping gears is a calculated investment, it's not for everybody and what works in one model/make of truck may not get the same results in another. AKA, putting 4.56s behind a 5.3L GM 1/2 ton might not work out the same as it has for those of us with Ford V10s and 4R100 trany's. I spent a bunch of time reviewing the typical speed I drive (towing & not), rpms I would see in each gear, Power and torque band of the engine, comparatively with several ring and pinion options and made sure to account for my slightly larger than stock tires. 4.56's fit my needs on paper and proved out to be right choice once installed. I would suggest anyone contemplating this swap to do the same, this is likely not a one size fits all exercise, and is also not a cheap upgrade however cheaper than a new truck in most cases, lol.

As far as those talking about a supercharger, I've driven a V10 with a whipple charger and 3.73s. It was livelier but I wasn't blowin away by the performance. Frankly that truck could have benefited significantly with deeper gears also and this wasn't even in a towing scenario. On top of that, you added more mechanical pieces to the puzzle, increased cylinder pressure considerably, and have effected the overall reliability and durability of the engine, transmission, and drivetrain. If I was only going to do one, I think you can guess which it would be. On the flip side, if you have about 8k you want to sink into your decade old truck, combining both would be awesome however I'd probably just upgrade and buy a used oil burner then. Food for thought.

One last thing to consider, originally when ford came out with the V10, they were available with 3.73s, 4.10s, and 4.30s. In the last half of it's life and after ford had up'd the power and torque ratings, it was only offered with 4.10s or 4.30s. I assume Ford engineers had figured out the same as us that had done gear swaps and found those were the optimal sets for this combination.

What you say is true. I'm not sure if Ford Parts offers the lowest gears for the Sterling rear axle, but I'm sure they are available aftermarket.

On the supercharger front, and Fords apparent decision to no longer offer 3.73's for the later 6.8L three valves, I wonder if Ford didn't give up some of the low end torque curve, for the higher overall HP (as opposed to the two valve)?

I know that Ford went back to the two valve for HD applications.

Wes
...

Couple things I missed in my post; The Superduty Dana axles can for sure accept ring and pinion upgrades up to a 4.88 without an axle swap, not sure about anything higher as I didn't have the need to research it. Not quite sure what your trying to accomplish with your comparison of the 5.3 with 3.73s, that's apples and oranges. Swapping gears is a calculated investment, it's not for everybody and what works in one model/make of truck may not get the same results in another. AKA, putting 4.56s behind a 5.3L GM 1/2 ton might not work out the same as it has for those of us with Ford V10s and 4R100 trany's. I spent a bunch of time reviewing the typical speed I drive (towing & not), rpms I would see in each gear, Power and torque band of the engine, comparatively with several ring and pinion options and made sure to account for my slightly larger than stock tires. 4.56's fit my needs on paper and proved out to be right choice once installed. I would suggest anyone contemplating this swap to do the same, this is likely not a one size fits all exercise, and is also not a cheap upgrade however cheaper than a new truck in most cases, lol.

As far as those talking about a supercharger, I've driven a V10 with a whipple charger and 3.73s. It was livelier but I wasn't blowin away by the performance. Frankly that truck could have benefited significantly with deeper gears also and this wasn't even in a towing scenario. On top of that, you added more mechanical pieces to the puzzle, increased cylinder pressure considerably, and have effected the overall reliability and durability of the engine, transmission, and drivetrain. If I was only going to do one, I think you can guess which it would be. On the flip side, if you have about 8k you want to sink into your decade old truck, combining both would be awesome however I'd probably just upgrade and buy a used oil burner then. Food for thought.

One last thing to consider, originally when ford came out with the V10, they were available with 3.73s, 4.10s, and 4.30s. In the last half of it's life and after ford had up'd the power and torque ratings, it was only offered with 4.10s or 4.30s. I assume Ford engineers had figured out the same as us that had done gear swaps and found those were the optimal sets for this combination.

I made basically the same change about 5 years ago on my 2003 V10 powered Superduty. After upgrading campers to a 32' fifthwheel and then upgrading boats to a 20' Deep V fiberglass walleye boat, I found my truck struggling in the power department. Took it in with about 65k miles on the ticker, had them freshin the trans and swap the stock 3.73s for 4.56s. What a difference! before there was no option of pulling in OD, 3rd was normal and at times 3rd struggled and I had to drop to second. After the 4.56s, I could tow flat land in OD, hills in 3rd and very, very rarely every need to go down to 2nd. Since that time I purchased a larger 15.5k GVWR Cedar Creek and gave up on double towing. The truck handles the new camper exceptionally well and has no issues running down the highway at 65 mph very comfortably in 3rd and when not in the hills or wind, OD works also. I will add that before I swapped gear, I did do the y-pipe modification and also had added a custom tune from 5-Star performance. Those things remained after the gear swap with some updated towing tunes.

If it's primarily a dedicated tow vehicle, the gears are a must have and make a world of difference.

I Am with Hannibal. I am running 4.30 gears in the F 250 now. With all the gears and the OD's now a days, I will never go that route again.

A gasser BTW.

A 5.3 will put you about where you would be with 3.73 and OD locked out, which is what is going to happen anyway when you hit a grade. If that's not enough, the transmission can drop down yet another gear and with 3.73 you'll be able to run at least 50 mph without getting close to the 5800 rpm redline of the V-10. My truck with 3.73 gears and 16-inch wheels does the 2-3 shift at about 60 mph on hard acceleration.

If you want to tow up hills in overdrive, you might consider 4.10 gearing, which is probably about as far as you can go with ring and pinion gear swaps. There are heavier Dana axles with 4.56 and 5.38 gearing used in Ford chassis, but that might mean an axle swap, not just a gear swap.

D@mn. I was hoping you got a supercharger!

klr650goldwing wrote:
Wes, that was a wonderful diversion. I have a 305 Dream very similar to yours. And always wanted a Scrambler. That is a nice collection you have. Thanks for sharing.
If you ever plan to travel through Eagan, let me know. Maybe we could get together and talk bikes.

Thanks, Greg. It might be a possibility to discuss bikes someday. Love to do it. I have a relative in the Brooklyn Parks area that I see once or twice a year. I wish it was more and hope to eventually talk my DW into extended camping in the region, that we have more time to visit.

While I no longer have the Dream, I have five street Hondas plus the Scramblers. It's a long story. I also have three off-road Enduros. If I had recently sold my old WR490 Maico in a timely fashion, I would have the electric-start Yamaha WR250R on/off road bike by now. Obviously otherwise, yes, I'm ready to downsize. Honest... DW!

Hannibal wrote:
Brings back memories of my Honda CB360 twin. I couldn't seem to ride it enough.

On the gears, I've had all from 3.07 to 4.56. I've concluded for all around towing and empty highway, I like the 3.73 the best. Direct and first under drive for the gas hogs and O/D to direct for the rattlers. 3.73 seems to match the powerband of the engines.

Like you say, the 3.73 scenario fits my needs right now too. But if I pulled more weight, and didn't use the tow vehicle for other transport a lot, what Greg did makes sense to me now. He might only give up 1 mpg empty, not a bad compromise. The performance gains speak for themselves.

The memory of swapping wheels on my old Honda Scrambler, to re-purpose the performance comes back. One thing I particularily remember is that with the small 18 inch wheel, knobby and big sprocket, the gear ratios also seemed much closer together for hard acceleration uphill. OTOH, the 19 inch rear wheel with the street tire and small sprocket was a wonderful, low vibration set-up for casual highway cruising. After I got used to it, it took about 5 minutes to swap and literally changed the personality of the bike. The wheel swap was close to a Gear Vendors two-speed, a handy item on a 2wd truck... or a heavy CB900c bagger.

Wes
...

Brings back memories of my Honda CB360 twin. I couldn't seem to ride it enough.

On the gears, I've had all from 3.07 to 4.56. I've concluded for all around towing and empty highway, I like the 3.73 the best. Direct and first under drive for the gas hogs and O/D to direct for the rattlers. 3.73 seems to match the powerband of the engines.

Wes, that was a wonderful diversion. I have a 305 Dream very similar to yours. And always wanted a Scrambler. That is a nice collection you have. Thanks for sharing.
If you ever plan to travel through Eagan, let me know. Maybe we could get together and talk bikes.