When I am driving and under Eco mode (Possibly MDS, hard to know) I hear and audible click or clunk. It happens any were from as soon as I see the eco display to any time afterwards but in most case within 30 seconds of the eco being displayed. It only happens when accelerating and only when with the transmission is in D (i believe manual mode disables the eco display and possibly MDS)

I have taken it to a dealer and they say nothing is wrong and they cannot hear anything which is just not possible. They said "there were no errors in the computer so everything is fine". I notice they drove it .3 of mile during a test drive, so I doubt they did any thing.

My truck is 2010 Crew Cab, 5.7L, Auto, Big Horn Edition. I have added a K&N CAI but nothing else. I noticed it at around 10K but thought it was the AC clicking on and off. Its steadily getting worse. I am at 21K now and today driving to work it was really bad. I usually only here it once or twice per "acceleration". However, today I was getting the noise going down the highway when eco mode was active (for example as I approached a semi with a van trailer)

its hard for me explain the noise. I think it is some event the truck's computer is doing intentionally but I do not think it should be making this noise. Like I said it is kinda like the click of the AC compressor coming on but at 30 degrees today that should not have been happening. The noise is coming from the engine compartment area and I hear on the right side of the truck as I am driving. It is not a rattle or knock. I happens on perfectly flat roads going in straight line.

I thought maybe it was the brakes drying the discs but it happens even on 90 degree summer days.

Any suggestions or ideas would be helpful. I am pretty easy on the truck so I am in eco mode quite. I can tell sometime when MDS is on, I can feel a little pull and I can sometime feel it in the pedal and hear it in the exhaust. My thought was this was MDS coming on when in eco but I have no concrete way of knowing.

Thanks

 

Usually clunking sounds are associated with the drive train, transmission, drive shaft, differential and sometimes steering linkage. Some trucks have had problems with the differentials and I think your truck may fall in this area.

Check for recalls and RRT's. It could also be your torque converter locking and unlocking, this would be another item to check into.

In any case take it back to the dealer and test drive it for them with the mechanic with you and point out the noise when it happens. Some techs may not hear the problem when they play the radio to loud.

 

I had an issue on my 2011 sport and it was a bad MDS ( Multiple Displacement Solenoid ) It was only one that went bad but when they had it apart I replace all 4 of them. It would make a clicking sound like a playing card on a spoke bike wheel. when I had it in tow haul mode it would not make the sound. just something you could check. There are a few videos on you tube you could watch and see if it sounds the same.