Hi, I'm new here. I have a 2003 3500 dually. When I am accelerating under normal load, at around 45mph my trans shifts into overdrive and the tc locks up at the same time resulting in quite the clunk. Almost sounds like something hits the exhaust line. if I accelerate more briskly, they engage at different times, and it is smooth as silk. This may be unrelated, but when ascending a hill with my trailer in tow, the tc will not unlock. It doesn't disengage until it makes the 4-3 downshift which can sometimes put me in the red zone at interstate speeds. Any help or advice is greatly appreciated. Just so you know, it has 165000 miles, but has been doing this since I bought it just over 2 years and 40,000 miles ago.

 

 

I have this same problem I only have 55k. Mine only does it when I hit 45 mph at 2 rpm. If anyone has any info on this I'd greatly appreciate it! Thank you!

 

sounds like mine. it can't be good for whatever is making this awful noise.