MDS and harsh downshift

brent · Post by **brent** » Tue Dec 23, 2008 12:57 pm

I have a 2007 Dodge RAM 1500 4x4 QC

With CROM 9r02 I am experiencing a hard downshift when it comes out of MDS and downshifts at the same time? Upshifts are fine.

Please help.

thanks

07HemiR6 · Post by **07HemiR6** » Tue Dec 23, 2008 1:44 pm

Are you sure its downshifting? You might just be feeling the torque converter locking/unlocking when coming out of MDS. When running a programmer, coming out of MDS feels harsh compared to running stock.

brent · Post by **brent** » Tue Dec 23, 2008 3:08 pm

Thanks. It doesn't seem to shift harsh when leaving MDS, but it does raise the engine RPMs by about 300. I believe it is only when downshifting and coming out of MDS at the same time. It does not do this with MDS turned off. I am running the 93 tune. Also this happens with only gradual acceleration.

That begs the following questions.

Are the part throttle shift points and firmness the same on all 3 tunes?

What is the difference between the 3 tunes? e.g. Is it only the spark advance or is there air fuel differences, etc.?[/i]

Post by **mikel** » Tue Dec 23, 2008 3:11 pm

Spark is the only difference in these tunes.

jtfinklea · Post by **jtfinklea** » Tue Dec 23, 2008 4:01 pm

We LX guys with the 5.7 and MDS have called this the MDS Bump or Pulse due to Torque management being effected by the tunes. That is why you feel it with MDS enabled and not so with it disabled. I had it before the predator when I changed my exhaust to Magnaflow. But it was most noticable when I installed the first tune from diablo.

brent · Post by **brent** » Tue Dec 23, 2008 7:32 pm

Thanks. It was the worse at initial installation of tune and it seems to be getting better. So the RPM change must be due solely to the fact that you are going from 4 to 8 cylinders with the same throttle position?

07ELECBLUE · Post by **07ELECBLUE** » Tue Dec 23, 2008 11:07 pm

No, it is not due to the 4 to 8 cylinder swith. The way that Dodge set it up was that when it went into MDS, it would partially unlock the TC. Going from full lockup while not in MDS to partial lockup in MDS causes the RPM change. They did this so the truck wouldn't bog down while in MDS. As a service manager so politely pointed out to me, it does say it will do this in your owners manual. I took my truck in numerous times to Dodge about this. I hated it. As soon as I got my DS, I turned off MDS and never looked back.

ZMagnum · Post by **ZMagnum** » Wed Dec 24, 2008 4:11 pm

OK, well indirectly it's due to the 4 to 8 cylinder switch then.

need-a-cage · Post by **need-a-cage** » Sat Dec 27, 2008 1:23 pm

07ELECBLUE wrote:The way that Dodge set it up was that when it went into MDS, it would partially unlock the TC. .

I am glad that I read this. I was going to turn MDS back on to see if the mileage would go up, but I hated this rpm increase as well. I thought it was the MDS, but it didn't sound like it kicked into 4cyl mode. It was doing it around 67mph. Does it do this right before it kicks into MDS and then if I didn't slow down enough it would not go into MDS and would eventually lock back up? I'll have to check this out on my next tank. I did not like this at all because the exhaust is almost silent at 67mph and 1800rpm and then it would unlock and go to 2100 rpm where you start to hear the exhaust, so it is really annoying to be cruising on level ground with no change in load or throttle position and you keep hearing the exhaust note come and go as the RPM keeps going up and down.

brent · Post by **brent** » Tue Dec 30, 2008 11:22 am

I had an Edge tuner for a while and it had a PID that would tell you when you are in MDS. The exchaust drone always occurs when the Edge indicated 4 cylinder mode. I did not have the drone before I replaced the factory exhaust with a cat back aftermarket exhaust.

My 2007 RAM 1500 Hemi locks and unlocks the torque convertor all the time when it is in 4 cylinder mode, and shifts roughly when the transmission downshift occurs at the same time as the 4 to 8 shift (I believe this is what I am sensing).

Around town it locks and unlocks the torque convertor a lot, and increases by 300 in 4 cylinder. My tests so far around town indicate a little better mileage. My concerns is that the torque convertor is constantly locking and unlocking and that it downshifts a LOT more often in the 4 cylinder mode . I also find the 8 cylinder throttle response is far better and eliminates a bog when accelerating from a stop as well as adding delayed throttle response at other times.

I believe I am getting a little better mileage with MDS on, but the vehicle is so much more driveable with MDS off, but I am not sure I will keep it off, since it drives so much better in 8 cylinder mode and cuts some wears and tear on the transmission.

RandTx · Post by **RandTx** » Wed Dec 31, 2008 7:59 pm

mds is a tad goofy in itself. mine would do some harsh ins and outs of mds occasionally with the stock tune or any tuner.
I've never run the DSP with mds on so don't know if it's any different or not.
Your mds sounds like it behaves as poorly as mine does so might be best to just turn it off like most of do.
I've seen little to no difference in hand calculated mpg with mds off although the over head claims it gets worse mpg mds off.
.

millertime · Post by **millertime** » Thu Jan 01, 2009 9:38 pm

I'll start with I have an 07 300C, just installed my Diablo last night. This morning we took the car for a drive for the first time since install and I experianced what ya'll are talking about. Am I correct to assume this is the same thing in my 300C as Brents truck? I have one more thing to add, at the same time I feel the mds/torque convertor bump I can hear a ticking noise that goes away after the switch is made out of mds. I installed the 91/cai tune then found out I had 1/2 tank of 87. Wife put gas in the car without me didn't know it wasn't at least 89 like normal. Any help is greatly appreciated.

Quick · Post by **Quick** » Fri Jan 02, 2009 2:02 am

All the 5.7 MDS will give the same effect. Log for ST KNR for the ticking. was it that kind of ticking?

millertime · Post by **millertime** » Fri Jan 02, 2009 8:19 pm

I'm still learning the terminologies what is ST KNR? I can tell you it's very faint and definantly happens right at the point the mds is kicking off. Shut the mds off a minute ago, getting ready to go out with the Mrs. will see if it goes away.

"edit" With MDS off that problem is gone, I do still hear a faint ticking noise but I think I'm starting to understand what causes that.

need-a-cage · Post by **need-a-cage** » Mon Jan 05, 2009 4:33 pm

ST KNR is short term knock retard. This is not what you are hearing though. I am sure you are hearing the EGR. Do you have a cold air intake on your car?

I put a CAI on my truck and the EGR is so loud that I am putting the stock box back on. It sounds like an exhaust leak on the manifold. It is loud as hell, but I never noticed it with the stock airbox. I only had it for a couple weeks though with the stock intake. The EGR opens and closes all the time at part throttle. If I hear the noise I can usually get it to go away by rolling on the throttle a little more.

MDS and harsh downshift

MDS and harsh downshift

RE: MDS and harsh downshift