RAM 1500 Diesel Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
111 Posts
Discussion Starter #1
Hello Everybody! Im new to the form, but been lurking for a few months reading and doing lots of learning. First I must say this form has really educated me on this truck and its pro's and cons. I'm on the verge of buying a 2016 ED (did my first test drive yesterday and just LOVE the truck). After doing all the reading on the forum I've decided a GDE tune is going to be my very first upgrade, so with that in mind, is there an axel ratio that's best for this tune? During my test drive I drove the 3.92 - noticed the truck turned about 2k RPM at 75 - and seemed like the tranny wanted to keep the RPM right around this 2k RPM range in each gear... (is this the same on the 3.55?) this made me wonder is this the best RPM with the GDE tune too? Will the 3.55 drop that RPM significantly and does a few hundred RPM really matter? I don't tow much - maybe 8-10 times a year and all my trailers (3 place snowmobile and very large pop-up trailer) all around 4,000 lbs loaded. Most towing trips are 3-6 hour drives, so not short trips, but all flat land driving. I know the axle ratio has been discussed in depth with each having their own application and opinion for the 3.55 vs the 3.92, but I guess I'm just wondering if one really optimizes the GDE tune better than the other given where the power curve is? Or am I completely over analyzing this and it's just a non-issue? For me I would really prefer the 3.55 but don't want to make the wrong decision. This will be the most I've ever spent on a vehicle in my life - so don't want any regrets:) Thanks for your input!
 

·
Registered
Joined
·
1,895 Posts
If you're driving 75 you'll see better MPGs with the 3.55. I drive 78 everyday to work and it's mostly rolling hills. I average about 23 MPG. I cruise in 8th and RPMs are about 1800 rpms. The 3.92 rear end will take a decent MPG hit at those speeds because of the increased RPMs.

The GDE tune doesn't care what rear end you have. If you are looking for ultimate MPGs then 3.55 is the way to go. If you are all city driving or just want something zippier off the line the 3.92s will be a little bit better. If you're towing heavy (over 8500 lbs) then 3.92 will be better.
 

·
Registered
Joined
·
12,664 Posts
First post - Welcome!

You just got good advice. Pick the ratio that meets your needs. You have all light trailers. Mostly it's flat. I think your decision should be obvious.
 

·
Registered
Joined
·
2,315 Posts
I am a fuel economy guy. I bought mine off the lot with 3.55 gears. I tow a full profile travel trailer at 60 mph, but not more than 65mph, and with the T/H mode on, it likes 6th or 7th gear, depending on the terrain. On my trips to work, I usually run the same, 60 to 65, and the RPMs are real low in 8th, and no issues with the rolling hills. Only when I run 55 (Ultra Fuel Economy), it will sometimes downshift on a few hills.
 

·
Super Moderator
Joined
·
2,524 Posts
Welcome. As others have stated pick the ratio that fits for you. I also have 3.55. With the 8 speed trans gear ratio isn't as big of a deal as years ago. The trans has plenty of options. GDE will without a doubt be your best upgrade.
 

·
Registered
Joined
·
167 Posts
The other consideration is when it comes to backing up with a trailer, then the 3.92 makes a bit of a difference.
But that has nothing to do with economy or the GDE tune. Just extra info. My 3.55's work great for me.
 

·
Registered
Joined
·
17 Posts
With the double OD of these transmissions the RPM difference in 8th gear at 70mph is less than 100 RPM, so I don't see a real big advantage in the 3.55's, but the 10% difference between the two can be a help with heavy loads or holding a gear while towing.

As always, the aero load is a much bigger factor in MPG than is gearing. Want better mileage, slow down.
 

·
Registered
Joined
·
4,225 Posts
With the double OD of these transmissions the RPM difference in 8th gear at 70mph is less than 100 RPM, so I don't see a real big advantage in the 3.55's, but the 10% difference between the two can be a help with heavy loads or holding a gear while towing.

As always, the aero load is a much bigger factor in MPG than is gearing. Want better mileage, slow down.
I calculate 1800 RPM x (3.92/3.55) = 1977 RPM
The difference is 1977 - 1800 = 177 RPM

With the torque that these engines have, I doubt that there would be little noticeable performance, or mileage, under most driving conditions, except when heavily aero or weight loaded.
 

·
Registered
Joined
·
2,315 Posts
1 - 11 of 11 Posts
Top