How critical is axle ratio?

Huntindog wrote:

Terryallan wrote:

Huntindog wrote:

dodge guy wrote:

Huntindog wrote:

Groover wrote:
Bottom line is that drive shaft RPM is irrelevant. What really matters is whether the engine is in its power band when you need it to be. Back when truck transmissions only had a 2.5 to 1 spread between high and low axle rations where much more important than they are with the newer transmissions that have a 7 or 8 to 1 spread.

The op is correct, unless you find yourself in first gear wishing that you had a deeper gear or in 10th gear wishing that you had a higher gear you get the same effect by simply changing gears.

I do suspect though that axles built with higher ratios may also be built to handle higher torque to the wheels, at least in some cases.

We have a winner. Rather than write all of this again, here is the readers digest version.
GM was late to the party of increasing their HD lines tow ratings. Ford and Ram were first, and they required higher (numericially) ratios to do it. When GM tried this approach, the Pinion gears would not live behind the Dmax. For those that do not know: as the rear end gears increase numericially, the pinion gear engages less of the ring gear, and thus is weaker.
So though the Dmax was more than capable of a higher tow rating, the gear set to make the performance acceptable was out of reach.
Enter GMs new Allison 10 speed. With lower gears available in the tranny, the rear gearset could actually be changed in the direction that would make it stronger. So that is what they did, and for good measure they increased the size of the ring gear on the duallys as well.

What I get out of that is that GM’s axles are weak. No other manuf had that issue with lower gears.

That is one possibility. But it is unlikely....I do not know who the axle suppliers are for the different brands and for what years, but I have read that for some years/models the same supplier sells to more than one manufacturer,,, even so, I doubt that one brand of axle is much stronger than another. A 11" inch ring gear is the same size in any brand, and the steel will be the same as well.
What is more likely is the Dmax actually puts out more power for longer.

There is a lot of evidence to back this up over the years.... If one chooses to look at it.

Actually that is not true. I made ring, and pinion gears for 23 years. each company has different specs for the steel used in their gear sets. There are a infinite number of metal combinations, and each one has a different heat treat spec. How long it is heated, how hot, and how it is quenched.
It is true that one supplier, supplies many different manufacturers, and each manufacturer has different quality demands. Different metal combinations, and different tolerances for quality.

Dana Axle makes the majority of American truck gear sets, and axles. Or they did 2 years ago. GKN Driveline makes axles for SUVs, and vans, and some passenger cars. They supply BMW, Ford, GM, Fiat/ Jeep/Chrysler, and Maserati. And yes, some are weaker, and some are stronger than others. it all depends on the application. after all the axles in a Chevy Equinox, don't need to be as strong as the axle in a Maserati.

Fun fact. Many ring gears are no longer bolted on. They are welded. However you still have to change both the ring, and pinion if you ever need to replace one or the other. They are married together through a process called Lapping.. During which they are run together with a abrasive compound spraying on them, under high torque to "wear" them together, so that they will run quietly. Then they are put into a testing machine to see if they indeed make noise. If they pass they go to the next step, if they fail. they are scrapped, and sent back to be melted down.
Then when they are put into the axle, they are tested for noise again. It is a very interesting process, well at least for the first year.
So if you have one of the makes we made axles for.. and it moves when you press the gas. You can thank.... me. LOL

BTW. Each gearset has 2 sides. A Drive side, and a Coast side. and they are exactly what they say. But in general. One side is always harder to get right. If your vehicle is quite going down the road, but roars when you let off the gas. You have a problem on the coast side.

So do you think there is an appreciable difference in the HD truck axles among the big 3?

It doesn't really matter in this conversation if a Maseratti has stronger axles than a Yugo. I would expect that to be the case.

I merely answered your statement that all manufacturers used the same steel, and all have the same quality . Short answer is. they do not. There is a vast amount of difference in the steel used by each company. Some steel is brittle, and some isn't. some have to be shotpeened to relax the steel so it doesn't break. It isn't all the same.
Could it be that one company or the other used a more brittle steel for a while? Yes it is entirely possible. Ford had a recall on the ring, and pinions in the 2004 F150s, because of bad steel.