I am looking at 2011 Ram 1500 Big Horns and am specifically looking at two right now, one of which has the Anti-Spin Rear Axle Differential and the other does not. My wife has a horse and we will be towing it occasionally although not frequently. Does anyone have any information on how beneficial or detrimental that Anti-Spin Rear Axle Differential is to towing capability, as well as the 3.55 vs. the 3.92? Any insight at all would be helpful, thanks for your time!

 

They are both engineered to pull whatever the specified towing capacity is, so whatever it says it can tow(usually on the sticker, but if not, on the door information plate), will usually be the same and fine in both rear ends. Anti-spin I am assuming is referring to limited slip diff. If you are towing in mud, snow or loose sand, it would be better for traction. The 3.92 ratio should pull the trailer better on hills, but will usually get lower fuel economy. So if it were my truck, I'd get the 3.55 for economy and limited slip for traction. My 98 has a limited slip differential and it has saved my bacon out on my property where there is a lot of loose sand and silt, while pulling a heavy trailer. A non-limited slip diff would have left me digging a hole with one tire instead of pulling out with both wheels. Just my $.02.

 

Okay, outstanding man thank you. So correct me if I'm wrong, but what I'm assuming from what you said, for non-towing and non-slip surface use, the 3.55 would be better for stop-go traffic fuel economy and the LSD would not make much of a difference on surfaces which are generally conducive to traction?

 

I initially inverted the #'s. The higher the ratio, the better the fuel economy. The lower ratio, the better the pulling power. If you are on a solid surface, there is no need for limited slip. But if you're ever going to be in a limited traction situation, limited slip is the way to go.

 

I have limited slip on my 98 and for the loose sand and silty conditions I pull loads through, it keeps me from getting stuck.

 

http://www.trucktestdigest.com/axle%20ratios.htm

This explains it better than I can.

 

If it has 20" wheels, you really want the 3.92 because the tires are 33" tall. I have 3.92's in my 08 (same transmission with 2 od's) and at 70mph I am only at about 2000rpm. The 3.55 will get worse in-town mileage because the engine works harder to get up to speed.

I have the anti-spin and it is nice is slippery/loose road conditions since both wheels are pulling.

 

Thanks mantisman, that was very insightful. Essentially it's saying there is next to no reason to get the 3.55 because the fuel economy is only about .4 mpg better, and as the other "man" says, it seems 3.92 would be better for city. The prospective trucks I'm looking at all have 20" wheels, so that would apply. Thanks again.

 

Yes. A higher numerical value equals more turns of the engine per turn of the wheel. You will possibly see better city and towing mileage with the 3.92s. And you won't ever notice a difference in normal driving with limited slip. Its when you don't have it that you see that sad, buried, muddy difference. You'll never know its there while you are on hard surfaces.