Why 4.1 axle?

time2roll wrote:

JRscooby wrote:

time2roll wrote:
The good thing is that for about $1,000 per axle you can have about any ratio you want.
Just seems lower cost to have it built at the factory as you want it so as to not pay twice.

Knowing what I know, and adding what I can imagine I can see how if somebody ordered a different ratio it would not cost much to set up that gearset, but all the other changes needed could get pretty high. The cost to get it blended into the stream at just the right time might also be high. Then add the possible cost of say the special speedometer gears and and rearend wound up on separate vehicles???

For many years optional ratios were offered and all seemed to work out. Yes in the old days it was a small gear swap at the end of the speedo cable as it entered the transmission tailhousing. My 2001 required a reprogramming of the vehicle computer. I understand now the speedo runs off the ABS tone ring in the differential so the axle speed signals the speedo and the ratio does not matter. Larger tires might require a reprogram.

I don't see any issue to install different geared axles as the trucks roll down the line. Make mine 4.30/4.88 ;)

Yes, in years past that was normal, a large range of options. And in fact larger trucks it is still a option. But starting I believe about 20 years ago the industry bean counters come up with a idea called "Just in Time Delivery" Instead of having large warehouse full of parts on the factory grounds, paying rent on the building and interest on the price of the parts. They have the parts come in from wherever unload of the truck and go on the line. It is a problem if any truck breaks down there is a problem. If it has a special part, it would be worse.
You talk of spending a grand to get what you want post delivery. I have changed both in a class 8 for about $1500 when the rearends where in good shape, only needed ring and pinion.