I have a 2011 Ram 3500 Mega cab dually with the 6.7L cummins diesel, automatic.

Had a head gasket leak at 92,000 km.  6 years ago.  Problem came up when towing my 16,000 lb 5th wheel RV.   Repaired at Dodge dealership in Alberta.  Heads were replanned to ensure straightness.  Upgraded head bolts to the stud kit and torqued to 90 ft-lbs.  Said stock was 65 ft-lbs.

Had another head gasket leak at 175,000 km.  This spring in April.   Problem came up right after towing my 16,000 lb 5th wheel RV.   Did another head gasket repair.  Head replanning not done this time.   Increased the head gasket torque to 125 ft-lbs.  

Now have 185,000 km on the truck and just had to add 3 litres of antifreeze as engine was spiking on high heat.  I towed the 5th wheel for 6 hours with no issue.  Problem came up right after towing my 16,000 lb 5th wheel RV and parking it.  Then drove another 3 hours empty with the heat gauge spiking whenever turbo kicked in hard to climb hills, and the heat guage returned to normal after hills.  I parked overnight and added the 3 litres of antifreeze in the morning.    I then did a 600 km trip empty, and the truck radiator did not loose any fluid.  Expect I would loose radiator fluid though when towing again.

My RV is only a medium load for this HD3500 dually, and I do very littel towing with the unit.  I would estimate that the truck has driven over 170,000 km with no load, so issue only came up when towing my 5th wheel.  Why is towing giving me repeated head gasket failures?  I purchased the RAM due to the good reviews on Cummins diesel.  Any thoughts on why I am having repeated head gasket failures?  Could it be my turbo is overboosting?  How would I know that?  Other suspected issues?

Thanks for taking the time to read my issue and provide comments.