busterja21 wrote:
i had an 08 dmax pulling about 13k up eisenhower and other CO passes. What i found works best is to put the tranny in manual shift,and keep the rpms around 2500 or slightly higher. engine temp sometimes climbs to 3/4 mark, but fan should kick in and bring it back down. seems counter-intuitive to the diesel to run at higher rpm, but it worked for me.
One the keys to keeping heat under control on the Duramax is to prevent lugging under load. This is actually true about all diesels. This usually means running in manual mode and keeping rpm in the sweet spot of the torque curve. Typically somewhere between 2100 and 2500 rpm depending on the model year.
if you run in "drive" the Allison is a bit slow to kick down under load -thus the need to run manual mode.
Also, if you don't hear that jet engine sound of the fan coming on as you near 200ish on the coolant temp - the fluid clutch on the fan has failed. Be aware that GM programs the coolant temp read out to be very static. It is a well documented item in the Duramax enthusiast world.
