[Keyrala]

Hello, my car has the 5.7 Hemi. I've noticed that when I am cruising at anything above 20 miles per hour then give it a decent amount of gas it doesn't downshift for 2-3 seconds. By the time it down shifts I have already gained 10 mph or so. I am giving it more throttle than it needs to downshift but it does not. When giving it gas from first gear in automatic mode it seems to work perfectly fine. I think it only has problems with downshifting.

I also noticed that when I give it a small amount of throttle (enough to keep MPH the same or gain mph slowly) with MDS on I feel a vibration in the car and it makes a way louder roar than normally. This roar seems to come from the front of the engine rather than behind me from the exhaust. Once MDS turns off it seems to go away. Since I thought MDS was a problem I bought a diablosport tuner and turned MDS off. It lessened the symptoms greatly but I can still feel and hear it sometimes. I'm bringing up the MDS problem because I think it is tied to the downshifting problem. I would like to get the problem fixed but there isn't a check engine light or anything.

When I was updating the computer software with the diablosport tuner a message appeared and the check engine light turned on and complained about transmission problems. Is that normal? As soon as I turned the car off and back on the light and message went away. It also appeared while adding the 91 octane tune.

Edit:
I just remembered one more problem. When giving it gas it also feels like it wants to go. Sometimes when it goes it reaches like 3k rpm then drops to 2900ish before going up again and shifts around 4k. I don't full send it so shifting at 4kish seems to be normal.

 

[RitzRT]

What's the mileage? Had the trans fluid and filter ever been changed? Have you put a code reader on the OBD port to see if there's any codes stored?

 

[Keyrala]

Mileage is 81300. I don't know about the trans fluid and filter. Code reader comes up with nothing.
Edit: It was a police car until recently at 79000 miles. If the charger maintenance schedule includes transmission fluid and filter changes then I am sure they did it. I just don't know at what mileage. Supposedly the oil and filter were changed every 3000 miles.

 

[RitzRT]

I wouldn't bet the farm on them doing the trans fluid/filter at that mileage. I'd start with that. Dump the fluid, change the filter, refill with quality fluid.

Hit your local Walmart for some Valvoline Maxlife synthetic fluid:

Robot or human?

You can get the filter at your local auto parts store.

Don't let anyone do a transmission flush. Dump and refill only.

Best,

 

[Keyrala]

Turns out the vibration and noise comes from a bad motor mount and wheel bearing (or so I was told). Also, this is my first v8 car and turns out the downshifting problem is me just being new to "modern" cars. My last car was a 2001. I was told that I have to press the pedal a lot more compared to older cars because it's a trick for gas mileage. It does downshift but I have to press way more on the pedal than I am used to. I apologize for wasting your time. I will still get the fluid serviced.

 

[GertFrobe]

Turns out the vibration and noise comes from a bad motor mount and wheel bearing (or so I was told). Also, this is my first v8 car and turns out the downshifting problem is me just being new to "modern" cars. My last car was a 2001. I was told that I have to press the pedal a lot more compared to older cars because it's a trick for gas mileage. It does downshift but I have to press way more on the pedal than I am used to. I apologize for wasting your time. I will still get the fluid serviced.

The tuner should have an option to firm up shifts on that transmission, enable that and see if it helps with the downshift behavior.

 

[Keyrala]

I know this is old but I thought I would make a post about the MDS vibration. I thought it was the motor mount causing bad MDS. However, I think it must have been a weak or failing spark plug. After replacing all the plugs with ngk iridium ix it runs smoothly. I thought this was interesting and just wanted to post.

 

[georgiapi]

Follow ups are a plus, even if delayed.