How fast are you going up these hills? Are the cooling fans running at high speed like they should be? Are the air coolers partially clogged with bugs/dirt/lint?
Slow down and drop a gear, back out of the throttle just a little bit.
'05 3.0L/Auto, AWD, 259k, stock engine and trans
'05 Dodge 2500, Cummins/48RE, QCLB, 4wd, some aftermarket goodies
'12 Buick Enclave, Premium AWD
'07 Honda VTX-1800T, tons of add-ons including electronic cruise control
'96 Honda XR400R, 426 sleeve, ported head, cam, carb, pipe, street legal