Why 4.1 axle?

Your reasoning is sound. The GCWR of the proposed truck with various axle ratios will give you explicit info on the capabilities.

Your reasoning sounds good, but with the 6 speed transmissions, 3,73 gears will result in less towing capacity and worse fuel economy. With the 4.10 gears, you start out easier and your transmission shifts through the gears as needed. You loose some top end, but likely don't ever drive that fast anyway. There are some spreadsheets folks have done showing the gears, rpms, etc.

My brother asked what I had on my truck and what I would order differently, I would order 4.10 gears (did not think about it with 6pd trans enough) and I forget to get the 5th wheel prep (we tow bumper pull now, but wanted to ready for 5th wheel if we changed later).

He bought a new truck just like mine, except 4.10 gears and he loves it towing their ~10k lb trailer.

Note: we both have gas trucks, diesel I would get the 3.73

My Ram 3500 SRW only came with a 3.4 rear end. I was worried but it tows great. Buzz up every hill in the western US without breaking a sweat - with a 12,000 lb toy hauler.

Flashman wrote:
My Ram 3500 SRW only came with a 3.4 rear end. I was worried but it tows great. Buzz up every hill in the western US without breaking a sweat - with a 12,000 lb toy hauler.

Gas or diesel?

While I guess technically the 4.10 might hurt your MPG slightly I suspect it's hardly enough to even notice. If you're talking a GM truck I'm not sure you have a choice; I think gas automatically comes with 4.10.
In any case, other than the possible MPG penalty every other aspect of towing a load should be better with the lower gears. I'd keep the 4.10, you never know when you might want a bigger trailer or decide to drive over the Rockies.

IMO, the slight difference in ratios of these modern trucks is one of the more over-stated things that gets talked about often. Slowing down 1mph would likely save far more fuel than the ratio change. And, with these modern transmissions even the most experienced driver would be hard pressed to notice any difference.

Sure, if you're ordering a truck, get the ratio that fits your needs most closely.

The Ram message board I hang out on had some guys go from a 3.73 to a 4.56 and they all love it. Some even reported BETTER mileage around town. I can understand a change that significant but the slight 3.73 to 4.10 is pretty minor.

Flashman wrote:
My Ram 3500 SRW only came with a 3.4 rear end. I was worried but it tows great. Buzz up every hill in the western US without breaking a sweat - with a 12,000 lb toy hauler.

I towed 29k combined with 3.42’s in 5th 1,750 rpm at 60 same as 4.10’s in 6th at 60. Only issue was getting the load rolling on a steeper grade. If I had the AISIN in the 11 DRW it would have been perfect.

solismaris wrote:
My reasoning is I can just use a lower gear if necessary. With the new 6-speed transmissions now common there should be plenty of gears to chose from. If that would work, why suffer the lower economy of the 4.1 ratio when I'm not towing?

It depends !

Many of the >4 speed automatic transmission just space the gear ratios closer together and do not increase the range. In this case, you would still need the 4.10 rear axle.

Take the 1st gear ratio of your current transmission and multiply it by 4.10. Then take the 4th gear ratio and do the same. That is your effective range.

Do the same for the new transmission and compare the results. What you want to see is if 5th or 4th gives you the range yiu had before.

My old E150, 4 speed, (retired from any long haul towing) came with a 3.73 instead of 3.46 was a good combination for what I was towing.

4.10 is for this:

The more speeds in the transmission, the less the rear ratio matters. If your next truck is a GM or Ford, it'll likely be a 10 speed.