Hammer, thanks for your quick reply. I believe the torque answer from the 4X4 shop referred to torgue as measure at the rear wheels. I'm not an expert but maybe I should try some of that dust you are snorting (sorry offering).

 

Ledoyle:

Your right in that there are a few different ways to accomplish a gear change.

Assuming you will be towing often enough to make the bucks worthwhile, it depends on how quickly you want it done, and whether you can do the labor yourself or will be farming that out.

A point to consider is that the 9.25 inch axles were put into the RWD Gen 2 D's because 100% of the engine power and torque would be going to it.
The AWD D's like mine though got the 8.25 inch units because power distribution is fixed at 60 rear and 40 front by the transfer case.

Finding the correct axle assemblies would allow one to make the swap without having to worry about "setting up" the ring and pinion. That makes the swap a bolt in upgrade.

Swapping out your oem gears would take a shop with the tools and expertise. You would have a warranty on the work though, and if there is an issue you take it to them and say "fix it".

As of late, $1800-$2200 seems to be the going rate for a 4x4 gear change.

Consider this:
Possibly you could find a fellow D owner with the 3.92 gears who might let you take a spin with their rig and your trailer (or theirs) to see if the difference is worth the expense for you.

Don

 

Thanks Don, unfortunately, I don't know anyone with another Durango that I could ask. I think we gained enough experience last summer on a 2800 mile trip to know that I need to make a change. I either need a new truck or modify the one I have. On the straights with even slight hills we bogged down hauling out 28' 7000# trailer. It was annoying to us and to anyone behind us. At a minimum I'm hoping to be able to maintain more constant speeds on the highway. Another experience we had was when we unknowingly got onto a highway West of Sheridan, WY with a 7-9% grade. I really felt like we were seriously stressing the truck. I expect to still slow down on such a grade but not to 10 or 15 mph.

With the 3:55 the tow rating is 7400 lbs and with the 3:72 or 3:92 it goes up to 8900#. This is what I thought I had until we started towing.

I have another question about upgrading to 9.25" Rear Differential. That is will I run into a problem with the size of the 9.25 vs the existing 8.25". Specifically, length of the drive shaft, universal joints,etc. This seemed so simple when I started. Maybe I should just order the gears and have my 4X4 shop install them and let it go at that instead of trying to make the truck something that it isn't. Anyone out there who can encourage me one way or the other? I appreciate others opinions. Thanks, Larry

 

Does anyone have a 9.25" Durango or Ram 1500 that can measure the back to front and middle top to end of the shaft where the u-joint connects? I'm trying to see if I'm going to be forced to also mess with the drive shaft if I put in a 9.25" in place of my 8.25" rear differential. Thanks, Larry

 

Factory specs for a Ram 1500 with 9 1/4" AAM rear goes up 1000 lbs. when going from 3.55 to 3.92 gears, although having the 20" factory wheels instead of the 17s gives it right back.

As far as a straight gear swap, my local 4x4 shop charges $600 per axle for ring/pinion/install kit/fluid and labor. $75 more for the 500 mile inspection and brake-in fluid change...

 

Thanks Hammer, I have the 17" wheels. If I were to swap in a new 9 1/2" Durango Axle Assy instead of upgrading the ring and pinion for the 8 1/2" rear do you think I'll run into any need to make universal joint changes, driveshaft or other difficulties if I stick with a Durango rear end?

I think I have to go with the 2wd rear end to get a 9 1/4" Any intelligence in the rear end like sensors, ABS, etc that I need to watch out for?

 

looks like the 9.25" and 8.25" rear differential use the same drive shaft. The dealer tells me that the transfer case is the thing that determines which drive shaft to use. There is one with the 144 TK and a different one with the 244 TK.

After doing all my research it looks like I will be ordering a used front carrier and rear axle assy with 3:92 gears. Then I'll sell my 3:55 assemblies after the 3:92's are installed and working. Net with labor I'm expecting this to cost between $1200-1500. Much less than the $2200-2500 I was looking at before.

 

Try some 28" tall tires, that will push the effective ratio close to 4:1 see if it makes any torque differnece.

 

Thanks for the suggestion. My research thus far tells me that I have to go with smaller tires to get add'l gear ratio change. Currently have LT245/70R17's my 4x4 shop tells me that I'd have to go to 225's to get add'l ratio change. Interesting academic topic but if the 3.92 change doesn't cut it I'm probably going to have to bite the bullet for a Dodge 2500/3500 diesel or a smaller trailer. I just spent $900+ on new tires last Summer.

I could also put a catback and a chip in if I wanted to eek out a few more ponies but at 5000+ feet we get a diminished return. Probably better to get bigger truck at that point.

 

I will throw this in there, I just bought a 2006 Hemi Limited AWD with 3.92's and most options for 14,500$.

If yours is paid off, did you do the math on trade in plus 3200-3500$ (gears, catback, chip) to see where you would be at for a different D or truck? Though I would say, if you are needing the power I'd go with a diesel...