2005 E320 CDI w/ 182,500 miles on odometer. Highway speed set to 69mph, engine RPM ~2k in 5th gear & everything rides out butter smooth w/ zero strange noises or vibrations & fuel consumption averaging 35-40mpg in instrument cluster... then I get into downtown & start encountering red light green light stop & go traffic w/ constant accel/decel & transmission shifting up/down through midrange gears. It doesn't happen always but I have begun to observe at speeds around 35-45mph, vehicle struggling to decide what gear it wants to be in 3rd or 4th so engine RPM sorta pulsates between 1000-1100 as if it's in a state of flux up/downshifting. Often, pushing harder or letting off accelerator pedal completely is enough to force RPMs to stabilize, transmission chooses a gear with certainty & stops the bouncy surging but trying to maintain a steady constant speed in that range will often bring it back. I've also been hearing a sort of rattle/vibrational sound coming from outside/underneath vehicle while accelerating & running up through the gears that starts around 1250-1750 RPM & smooths out & disappears completely once 2k RPMs is reached. Sound reminds me of what a heatshield coming loose in one corner might make as it passes thru vibrational harmonic frequency bands of dynamic pressure but I fear it's more likely internal to valve body or gearbox or maybe TC. Transmission control unit is not holding any stored or current DTCs in fault or event memory. Everything I'm describing used to only occur when vehicle was cold & warming up but once everything reached operating temperature, it would all clear up but so now it's doing it even after 30+ miles of highway driving & fully warmed up. I will do a transmission reset with accelerator pedal/key-fob to see if it just needs to relearn how I like to drive but I suspect some hardware component is starting to show signs of wear internal to transmission. I see there are a few 'actual values' I can monitor with DAS but have no baseline of understanding about what valve pressures or TC lock-up RPMs are considered normal. One other thing I forgot to mention is I had tranny serviced @162,000 miles filter changed, magnet cleaned (minimally dirty) & mechanic flushed red out & replaced it with newer blue. He said blue is backward compatible & runs cooler than red so I had no objections at the time, now beginning to question that logic. Is it possible blue never gets up to optimal temperature in a 722.6? Well that's my story & I'm sticking to it but thanks in advance for any/all comments, suggestions, opinions, ideas you might have & want to share.

 

I have a similar issue with my 05 CDI at 220K miles. My issues also happened after a fluid change. I used the MB red fluid. Rock solid at highway speeds but ~100 RPM fluctuation at 25-45 mph. Hills and cold temperatures exaggerate the condition. I hooked an analyzer up to the car to watch the engine and torque converter speed PID's. My torque converter is defiantly slipping. Planning on installing a valve kit, TCC solenoid, filter and fluid to see if I can get another year out of the vehicle. Good luck with your CDI.