2008 ram hami mds question

[Petrou]

My dad has a 2008 dodge with a hemi, four wheel drive, auto. now the mds system if i am corect is to cut out the cylinders for fuel economy purposes, correct? well i have yet to see this truck do that in 19000 miles of operation, down hills, flat land, it has never come on. it does have it on there i did confirm that. anybody else have this problem

 

[Gary Allan]

I don't know the answer to this ..but I think you just created a new nick name by mistake. Ramhami - it's got a good flow to it. ..but seeing that it's a popular question in such matters... What viscosity oil is he using?

 

[Anies]

If I'm correct you would need to use 5w20 in the truck otherwise it would prevent the MDS system from kicking in. 2 cents. A blurb from the Dodge Ram forums: http://dodgeforum.com/forum/3rd-gen-ram/149195-hemi-mds-question.html

 Quote:

The only way to tell if it is on is to listen for your exhaust note to change, or to watch your rpms on a flat raod. Youll be cruising along, say 1500 rpms for a minute, then, they will kick up to say 1800 all the sudden and you havent touched the throttle, that is the mds

 Quote:

They probably got that fact mixed up with the oil... Supposedly you have to use 5w20 in your Hemi for the MDS to work properly.... Gas, the MDS will kick in no matter what's in the tank....

 

[NHHEMI]

 Originally Posted By: Petrou

My dad has a 2008 dodge with a hemi, four wheel drive, auto. now the mds system if i am corect is to cut out the cylinders for fuel economy purposes, correct? well i have yet to see this truck do that in 19000 miles of operation, down hills, flat land, it has never come on. it does have it on there i did confirm that. anybody else have this problem

1 - There is nothing in the truck that tells you when MDS activates. It comes on and off by itself. There is no light or instrument panel indicator/message in the 08 Rams that tells you it is on. Unless you are able to hear it( there is a change in the exhaust sound when MDS activates )or feel it( on some trucks, like mine, you actually get a very slight skipping cylinder/fouled plug feeling at low speeds when MDS activates - at anything 30+ MPH and above it is impossible to tell by feel ). Other than a sound change or that slight skip feeling you have no way of knowing it is active. NOTE - the poster above who mentions the RPM change is correct however I have found that only to be true under 50 MPH. Under 50 MPH and your RPM's do jump a bit when MDS kicks on. However, out on the highway at 60 MPH in CC with MDS active the RPM's don't jump. Has to do with the OD gearing in the tranny. You do get a slight RPM jump when MDS kicks on at slower speeds. 2 - MDS only activates at low RPM, power demand, levels. GIve it any real gas or even have a moderately heavy foot and it will not come on that often. On my 08 it kicks on around 25 MPH around town if I accelerate easy. MDS will only work up to a certain highway speed and then it won't come on. I believe for 08 70 MPH is the cut off. 3 - Are you 100% sure the truck actually has MDS? "ONLY" the 1500 1/2 ton trucks have it. Actually, only the 1500 Regular Cabs and Quad Cabs have it. The 1500 Mega Cabs are actually built on the 3/4 ton platform and do not have MDS. No 3/4 ton( 2500 )or 1 ton( 3500 )trucks will have MDS. 4 - As another poster mentioned already a 20 weight oil is required for MDS to function properly. 5W-20 is the year round recommended weight by Chrysler but you can sneak some 0W-20 in there during the winter if you are in a cold climate. In addition to various computer controlled functions that control/cut fuel delivery and open and close valves during an active cycle the engines with MDS have special lifters that when the system activates collapse on themselvs. If you don't run a 20 weight oil it will cause the system to not operate properly. The system actually relies on oil pressure to operate properly. Don't run a 30, 40, or 50 weight oil if you want MDS to function properly. 5 - Pressing the button on the end of the gear selector once( Tow/Haul Mode )or twice( Overdrive Off Mode )will cause MDS to be deactivated. It will only operate in standard mode. IF your Dad sees the little Tow/Haul or OD Off light/message on the instrument cluster it has MDS deactivated.

 

[Petrou]

i put 5-20 in it. and now that you mention it, i do sometimes get the miss you speak of. rpm thing is also noticeable. so that makes sense

 

[Petrou]

oh and yes it is a 1500, quad cab. and i have noticed that it does kick on.