Brad~ .. Thanks for posting this a thread .. I have a question maybe , with you're experience you , or someone here can answer..
I put a 2004 Hemi in my 02' Ram Quad cab.. It does fine , but the transmission shifts 7 times and At 60 mph I'm barely turning 1,500 RPM's .. If I'm in town , 35 mph My truck lugs and I have to take the Overdrive off..After reading this thread , It accured to me that it could be my rear end gearing..I looked in the glove box and the tag says I have a 3.55 Gear..The truck came with a 4.7 and has the tow package and big springs , shocks etc.....
Does any one have any suggestions or know how I might get this truck to act normal ??
Thanks...
George..

 

George, after I do my 3.92 upgrade I'm going to have the computer flashed by the dealer to reflect the new gear ratio after upgrading from 3.55. You might talk to a dealer service advisor. Mine agreed to flash the computer for $48 (about 30 minutes work). Perhaps you need to have your computer reloaded. It sounds like it is having a somewhat irrational response to your engine change. The other alternative would be to put a computer chip in that would coast anywhere from $50 to $350 depending upon which one you choose. This permits you set shift points at your desired levels. Larry

 

I've thought about that. The Transmission shift point option on the Super chips usually cost a little more..$45.00 I think , but it's worth it..When I get the money , I'll buy one and post the results..
Thanks ....

 

Update on my rear axle swap 3.55 to 3.92 and 8.25" to 9.25". The rear axle assembly that I received had traction control where my old one did not. Thus the speed sensors are on the end of the axles instead of on the 3rd member. With there being two sensors instead of one, the connection will not work. My salvage yard is locating a 9.25" 3.92 ratio rear axle assembly without traction control (which I really didn't want anyway). It will cost me $200 more to make the swap but then everything should just go in like it was originally planned. This is the wonderful part of working with trucks! Oh, well. I should have the parts in a few days and we'll try again.

 

Ledoyle:

Thanks for the update!

Brad:
If your truck originally had a 4.7L engine, then you have the 545RFE trans which is a 5 speed.
The prior version of that was the 45RFE which had 4 speeds.
I am not sure that you can have 7 or even 6 speeds there.

Are your tires OEM or bigger? Larger tires would give you an effectively taller gear ratio which would result in the lower rpms and lugging you are seeing.

I have the oem 245/70/17 tires on my D, and I see around 2K at 70 mph.

Don

 

Update on my rear axle swap on my 2005 Durango. I have had to abandon going to the 9.25" rear axle. I ran into a problem that no one seemed to be able to solve. That is on my 8.25" Rear Axle the speed sensor is on the top of the differential. I had a salvage yard get two different 2004 Differentials from Durangos. Neither had the speed sensor on the top. The local Dodge dealer tells me that their pictures show two different 9.25" Speed Sensor (TC or none). Since my truck has been in the shop for over a week and I can't seem to find anyone who can tell me what the solution is I have decided to keep the 8.25" rear end and have a new ring and pinion installed at 3.92 ratio. The front carrier assembly has already been installed and looks like it works. I am interest if anyone has run into this. Was there a difference between the 2005 and 2004? Thanks, Larry

 

Larry:
I think you will be ok with the 8.25 inch unit. I also believe that the 04 and 05 years were the same as far as the axle assemblies went.

I am pretty sure the only way you could get a 9.25 inch rear end from the factory in a Gen 2 was to order a 4x2.

While I realize that places like Florida and California can get by without 4x4 unless the owners are off roaders, here in Ohio I think it silly to have a 4x2 truck or SUV.

Don

 

Don, I'm sure you and others may think me crazy or obsessed or both but after accepting that I couldn't get the 9.25" rear end and that I would resort to 8.25" upgrade to 3.92 I found another source for the 9.25". Several people told me that if I could get to the 9.25" the bearings, axle shafts, housing are all heavier duty and that it would be worthwhile if I could get there.

The rear end is supposed to be delivered today. I'm keeping my fingers crossed that it has the speed sensor holes on the top of the 3rd member. The traction control differentials to not have the speed sensor on the top of the housing, there are two and they are on the backing plates for each wheel. There is a different wiring harness to get out to the wheels also. More updates later in the day if everything goes okay so that someone else can avoid my frustration in making the swap. Thanks, Larry

 

Well, I kinda failed to locate a 9.25" 3.92 rear axle assembly for my 2005 Dodge Durango. After getting my third assembly that was incorrect I had my 4X4 shop install the 3.92 ring and pinion in my 8.25" differential. My truck sat at the shop for nearly three weeks while I tried to make this work. I tried locally in Denver and at a nationwide shipper and received the wrong parts each time. I'm frustrated but I'm done messing with the upgrade. Bullhide 4X4 in Fort Collins, CO was great and really worked with me to install my front carrier assembly that I bought in Denver and finally to install the ring and pinion along with the Master Bearing Kit for my "D".

I think given enough time and patience I eventually could have found the right parts but it was getting so frustrating that I finally called it.

I will tell you that there is a good difference in the responsiveness of the truck from a dead stop. If you get on it it goes without delay. Since I stayed with the 8.25" diff we reused the tone gear from the existing diff. Therefore, there was no computer flashing required as I would have had to do with the 9.25" change. My Dodge Service guys tell me that with the load I'm carrying (7400 lbs loaded) that I shouldn't have any problems with the 8.25". I have pulled this trailer about 3000 miles with the 3.55 gears and when we looked at the ring and pinion and bearings on the 8.25" there was no signs of wear or damage with 55K+ miles on the vehicle. Larry

 

Ledoyle:

Glad that you finally got some resolution on this event though it was not what you set out to do.

I think the 8.25 will do the job for you. As you found out though, looking for a D with the 3.92 gears is a bit of a challenge.

The surveys I have seen show that the 3.55 is the gear of choice on 66% of them.
It does not help that unlike Ford and GM, Dodge does not include the shorter gear as part of their tow package.

Both my 01 and 04 have the TP, and neither have the 3.92s.

When I was shopping for my second D, I tried to shoot for the shorter gear, but ended up giving in since I do not tow much and knew that the 3.55 would be fine.

Don