I didn't realize that. Thought it was tied to MDS. Maybe that's why I don't feel anything when eco light comes on and goes off.

 

Yep 3.92. No problems with in town driving.

 

I think I am confused by why people thinking that it a problem when they can feel that MDS is activated.

Of course you can/should be able to feel it. You engine is running on half the cylinders, thus half the horsepower. How could you expect not to feel that?

The idea is, for it to only activate when little power is need to maintain speed.

 

Yep, and that is a good thing........

 

MDS = Multiple Displacement System. There is no other definition, it means the engine is switching from 8-4-8 cylinders providing power. I don't feel it and other than looking down and seeing the "fuel saver" light come on, it's seamless. My truck is a 2009 with the EZD engine with 3.21 gears. I can't talk about the EZH engine and how that handles the MDS, but I suspect there may be a difference between the two. What many here think they feel when the MDS is kicking is not the MDS but the torque converter locking and unlocking concurrently with the MDS system.

 

You are absolutely correct, MDS mode is not in sync with the eco light at all and just monitors your driving habit. We have already had numerous threads on this back in 09 or 10. If some of you guys do, then you have a different setup because mine does not. However, I have a 2009 MDS manual that says eco light it comes on when in fuel saver mode. This manual is not correct for how it actually works though.

 

If it bothers you that much do as he said. Or buy a tuner and turn it off.

 

Outside of a tuner to turn it off completely, there are two ways to temporarly disable it: use the Tow/Haul button, or shift the truck into 5th. With Tow/Haul you're changing the shifting patterns of the truck, so you might actually be burning more fuel than without MDS in general. I know at least on my 2009 with Tow/Haul on it'll downshift a lot sooner than just normal mode. Shifting the truck just into 5th (it'll still downshift and upshift first through fifth) seems the best way to kill MDS for the trip. Neither solution is long term. The Tow/Haul will turn off if you turn the truck off, and the 5th Gear solution will turn off if you go into neutral, reverse, or park.

I've had my MDS turned off for awhile now with a tuner. In fact the only time it's ever turned back on is if it's going to the dealer for service or an oil change. Even with MDS via the tuner, the MDS light will still come on at various times while driving. Rather than see it coming on and off, I just turned it off in the truck's EVIC options. I'm not sure what it's doing, but it definately isn't putting the truck into MDS mode. With loud aftermarket exhaust and 4.10 gears, you can definately tell when the truck is really in MDS and you've gone from 8 to just 4. As the OP and some other posters have said, it's not bad on the highway, but sounds and drives terribly in the city.

 

I have a 09 Ram 1500 5.7 392s and I have never felt the MDS kick on or off. Everything is stock and I get 18+ city/hwy mixed and over 20-23 depending on how fast I am going on the hwy only. But I have never felt the mds and when I hit the gas I have never felt it bog down. Now I am wondering if the mds is working properly since everyone on here is complaining about it.

 

I say take it in and get it checked the ones who feel thinks or have bogging or mine is not working if there is that much noticeability when changing, I have the fuel saver light but disabled it to see if I can tell, man I must have one that works as stated, seamless but people are saying they can tell. Even if I put the light on and lets say go 40 mph and drive on a flat road and the light comes on and I am sure it must be one with perfect conditions but when I press the gas whether mash it or just a small increase I dont notice any change. Knock on wood. Getting fairly good mileage also, my wife drives it the most but I find I like to try to keep the light on when enabled she doesn't care. I think you have mechanical issues or they all run different. I am happy with mine except I had to change my GPS antenna since I was the one who installed the radio and the Nav quit cheap ebay antenna so I put the OEM one in all is well.
Good luck with the MDS issue.