Join Date: Apr 2009
Location: New Hampshire
Thanked 522 Times in 357 Posts
Feedback Score: 10 reviews
This is happening mainly on MDS equipped cars, correct? I have a co-worker that is a mechanical engineer that used to work in the design group of a major auto mfg. The MDS system induces a lot of vibration into the engine. You dont feel it because they put a lot of design time into dampening the vibration with the drive line mounts. Think of what would happen with a 1970 motor if you disconnected half of the spark plugs.
So it might be that if you hit a certain combination of RPM's and load, that you could cause part of the timing chain system to vibrate at a harmonic frequency that causes premature fatigue failure.
There's little doubt in my mind that the MDS is a contributing factor. My 2011 Jeep Grand Cherokee has the 5.7 engine with MDS and I can feel vibration at certain highway speeds, particularly when it seems the computer's deciding whether or not the MDS should be deployed or cut off because of a grade or need to accelerate where more power is needed. The transition is sometimes not as seamless as Chrysler portrays. I said this in a survey questionnaire that was e-mailed me after buying my Jeep. I often feel like it actually wastes more gas than it saves gas due to loss of engine efficiency while it kicks in and out. IMO, I'd rather scrap the MDS feature because I get crappy gas mileage anyway.
'16 8 spd SRT Go Mango with Sepia leather interior and sunroof, Speedlogix catch can, MOPAR splash guards, Drag Pack stripes, MOPAR 10 wheel center covers, other exterior cosmetic mods
'11 6 spd GWE SRT, ARH longtubes, K&N CAI SOLD
'10 6 spd PCP R/T Classic owner, custom Katzkin white leather interior. SOLD