Changing differential gears

I changed my Suburban's 3.08 to 4.10 and it's like having a new engine in there, much improved drivability towing or empty.

ScottG wrote:

I understand what your saying and I believe Ram's specs but if you talk to people who have gone from 3.42 SRW's and moved up to a dually with 4.10's, the driving experience is vastly improved even when not loaded. When loaded they're able to get off the line much better which is always a sore point with diesels. I'm hoping the fifth gens have an 8 speed trans to make the 3.42's more palatable (doubtful).

Of course that will do better off the line towing heavy, you are looking at 20% more torque going to the wheels with that change assuming everything else is unchanged.

Define "driving experience". If you are willing to give up some MPG, it will be faster accelerating running empty but really, modern diesel trucks are not hurting for power running empty. They have plenty good acceleration. But most people would prefer a couple extra MPG if they do any significant driving not towing.

It costs a lot. The best solution is a lighter trailer.

"I understand what your saying and I believe Ram's specs but if you talk to people who have gone from 3.42 SRW's and moved up to a dually with 4.10's, the driving experience is vastly improved even when not loaded. When loaded they're able to get off the line much better which is always a sore point with diesels."

Completely disagree with being "Vastly improved", sure the 4.10 takes off easier but unloaded I wish I could lock out first gear as you get rolling and it hits second.

The AISIN is key to making the 3.42's work well towing HEAVY. My Son has a 15 Limited 3500 4x4 SRW AISIN. I have towed his 14k dump trailer at a combined of around 26-27k, took off on a good grade with ease. My 11 HO Dually same gears on grade struggled at 28k. If the AISIN were in that truck I would be still towing with it even at my 33-35k loads.

Bottom line 3.42's/AISIN can't be beat for performance and fuel economy BOTH up to 29K+ !!!

If I get a 19 or 20 even at 35K I will most likely buy the 3.42's this time over the 4.10's. WITH THE AISIN!

Ask MeAgain of his 3.42/AISIN towing experiences.

valhalla360 wrote:

ScottG wrote:
It looks like our next RAM 3500 SRW will have to have 3.42 diff (unless they change for 2020 with gen 5) so it is entirely possible I will have them changed out for 3.73 or even 4.10 within a couple of years.

You are thinking of the old days with 3 speed automatics when you couldn't get a gear ratio that did what you wanted and the only way to make up for it was a deeper rear end at the sacrafice of MPG when running empty. With modern 6-10speed automatics, they are much better able to keep engine operating in it's ideal HP/Torque range.

It's important to look at the overall gear ratio (between the crank shaft of the engine and the rubber on the road).

To the OP: Take the new ratio and divide by the old ratio. That will give you a rough estimate of what percentage of pulling power increase you can expect. Speed up steep grades will still be limited by HP but if you are not making it up hills or struggling, it will do better relative to the change in ratio.

I understand what your saying and I believe Ram's specs but if you talk to people who have gone from 3.42 SRW's and moved up to a dually with 4.10's, the driving experience is vastly improved even when not loaded. When loaded they're able to get off the line much better which is always a sore point with diesels. I'm hoping the fifth gens have an 8 speed trans to make the 3.42's more palatable (doubtful).

ScottG wrote:
It looks like our next RAM 3500 SRW will have to have 3.42 diff (unless they change for 2020 with gen 5) so it is entirely possible I will have them changed out for 3.73 or even 4.10 within a couple of years.

You are thinking of the old days with 3 speed automatics when you couldn't get a gear ratio that did what you wanted and the only way to make up for it was a deeper rear end at the sacrafice of MPG when running empty. With modern 6-10speed automatics, they are much better able to keep engine operating in it's ideal HP/Torque range.

It's important to look at the overall gear ratio (between the crank shaft of the engine and the rubber on the road).

To the OP: Take the new ratio and divide by the old ratio. That will give you a rough estimate of what percentage of pulling power increase you can expect. Speed up steep grades will still be limited by HP but if you are not making it up hills or struggling, it will do better relative to the change in ratio.

Oh, for the days of the 9” Ford Differential....a couple of hours in the driveway , a chunk change-out (purchased at the local wrecking yard)....and drive away with the ratio of your choice!

Many people change gears to a numerically higher. I generally recommend changing at least two steps. So 3.55->4.10+ is beneficial. 3.55->3.92 is not (enough). Almost always with respect to towing, people are more pleased with the performance afterwards. Better acceleration, same to better fuel efficiency in city and towing.

Pitfalls: unloaded highway fuel efficiency and engine speeds. Costs. From an asset investment point of view, you will never get back what you spend. It will be $500-1500 per axle plus a tuner to change the transmission shift patterns. This could be a large amount of money on a 12+ year old vehicle.

As mentioned, selling the current vehicle and spending the extra $3k on a different more capable vehicle is generally a better $ investment. Full sized SUVs with much better geared 6-spd transmissions started in 2007 with Toyoda Sequoia and Ford Expeditions and 2009 GM twins.

However, if you really love your Durango, it is well maintained, it is a recreational/towing vehicle only and you can afford it, then I'm sure you will notice and enjoy the increased acceleration from stopped and better throttle response.

ScottG wrote:
It looks like our next RAM 3500 SRW will have to have 3.42 diff (unless they change for 2020 with gen 5) so it is entirely possible I will have them changed out for 3.73 or even 4.10 within a couple of years.

With the AISIN the 3.42's are good to over 29k combined SAE rated.

Change gears and you go from 100k coverage to 12k or one year.

Yes very happy going on 12 years after swapping 3.55 to 4.10 ratio.
Yes improved drivability both towing and unloaded.
Very worth it if you are keeping the vehicle.
No real downside except that I had to buy a programmer to fix the speedo.

Also swapped in Trutrac differentials that really improved off pavement traction. :)