This is the 2nd time its happened. (2 out of 2 times on the same hill at the same spot.)
One my way to the top of a grade, 55mph, 1000* egt, 9lbs of boost, coolant temp is at the "L" of "normal", trans-temp is 150*F (its a cool morning), OD-off. As I reach the crest of the hill and start backing off the pedal, something starts loudly growling and softly vibrating. As I continue another 30 seconds, the growl and vibration goes away.
Im thinking it might be the transmission, torque converter, or turbo.
Anyone have any ideas?
PrototypeMech

 

Fan clutch kicking in?
Sounds like the coolant is getting warm if its on the upper end of the gauge. Does the coolant temp go down after the growling subsides, or shortly after?

 

The fan clutch is already engaged and it runs smoothly. Its definitely something near the firewall or the transmission. I'm fearing my transmission is letting me know there's a problem.
PrototypeMech