Differential swap

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
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