D13 over heat when going over 70mph

You changed the radiator??

Did you (or shop) bleed all the air in the system? Also, maybe you need a new coolant reservoir cap (too relieve excess pressure)

 

Hope it starts on fire. Take insurance money move to Tahiti.

 

You can buy a bleeder funnel from AutoZone (check to make sure kit has correct adapter), then use the funnel to bleed out the air.

You will need to run the truck for almost 1 hour, with funnel attached, while max heat turned on, both sleeper & cab, and also bring & hold the revs up to cruise range for 3-5mins to "gurgle" out the air.

 

Sure sounds like stuck tstat not opening fully.

Given everything else that's been changed.

.

 

Obvious question but are you just going off the temperature gauge? Have you actually verified that the gauge is working properly?