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MDS or Tranny Noise, or ?

mdw3998

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2019 RAM 1500 5.7 Big Horn 62k
I get a weird noise when coming to a slow roll or a stop.
  • It only happens when I'm in ECO mode
  • Slowing down from 6th gear - about 35 MPH - coming to a "coasting" stop
  • The noise happens around 10 MPH
  • At 10 MPH:
    • the ECO light goes off which I assume is about the same time that MDS is disengaging and going back to 8 cylinders (?).
    • the tranny is downshifting into 2nd.
  • When I put it in Tow mode it does not happen - I know this doesn't disable MDS but it does change the shift pattern which may have something to do with this.
  • Sometimes I can duplicate the noise continuously, other times it will not happen at all (like with the dealer mechanic in the truck).
  • Below is a link to a video. Due to the wind noise, its hard to hear - it's much more obvious and loud real time. Listen closely at the 7 second mark.

Any ideas on what it may be or how I can narrow this down? Thanks

UPDATE: I found out how to disable MDS (- Gear Limiter, then + up to 8) and in non-MDS mode it doesn't happen. What could possibly be making that noise when MDS is going from 4 cyl to 8?
 
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theblet

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Can’t watch the vid at the moment. But when the eco light is off it’s running on all 8 cylinders. Tow mode does disable mds as far as I know. Try disabling mds by pressing the gear limiter button when you’re in 8th. This will disable mds but not change the shift points. See if it does it then.
 

mdw3998

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Thanks for your input. Yes when the ECO light is off all 8 are running. Tow Mode does not disable MDS, on the Gear Limiter you have to hit - then + up to 8 (for an 8 spd tranny) then MDS is disabled.

Per my previous update, with MDS off - no noise, with MDS on - noise. I replicated this back and forth several times.

So now the question is; what's making that noise when MDS goes from ON (4cyl) to OFF (8 cyl) when braking.
 

Richard320

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Thanks for your input. Yes when the ECO light is off all 8 are running. Tow Mode does not disable MDS, on the Gear Limiter you have to hit - then + up to 8 (for an 8 spd tranny) then MDS is disabled.

Per my previous update, with MDS off - no noise, with MDS on - noise. I replicated this back and forth several times.

So now the question is; what's making that noise when MDS goes from ON (4cyl) to OFF (8 cyl) when braking.
See what happens with the windows down. It might be the noise cancellation out of sync.
 

Bpebler

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If Tow/Haul mode is activated, MDS will not function. If it does, please show us otherwise where you came across this info. I’ve read several threads that state T/H mode disables MDS. In that event, the amber Tow/Haul button should be lit up as well as the green eco button in the dash simultaneously. I haven’t seen that happen in 84k combined miles with the 21 & 22 model year Ram 1500 I had/have & I can feel when the mds is active. Meaning to say that even with no eco light I’d be able to tell when mds is engaging & disengaging. Not a fan.

I drive in Tow/Haul mode nearly all the time even without a load or towing, & never does my green eco light come on. I USUALLY turn off MDS through the steering wheel also, except after getting out of reverse where it resets it & as soon as I see the green light I turn it off again - cheaper than a tuner that voids the warranty. This is just my preference obviously. I know people who have had issues with the 5th cylinder/MDS between 80k-100k miles. Personally, I get better MPG’s when T/H is active (vs. just turning off mds at the wheel) plus it’s more fun for the way I drive.


 
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Darksteel165

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I USUALLY turn off MDS through the steering wheel also, except after getting out of reverse where it resets it & as soon as I see the green light I turn it off again - cheaper than a tuner that voids the warranty.
Oh boy here we go again...
 

Mirowpl

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It could be what Richard320 points out. Listen with window up and down and see how it sounds. What I heard from your short video is not mds
 

Bpebler

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Oh boy here we go again...

I don’t have the standard Mopar warranty like I did on my last Ram, it’s through CNA. In my situation and the context I am speaking about it will void my warranty, already checked ahead of time. Maybe not in his situation, but he obviously keeps his turned on.

Edit: I know I can simply take it off/put it back on prior to servicing but I drive so much that I get monthly oil changes/tire rotates & it’s more of a hassle for me to want to do.
 
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