Gear selection

[Michael Turnipseed]

This question could result in multiple opinions, I have thru posts tried to come to what would be speed vs Rpm vs gear selection.
Running thru CA with a 6 speed C12 505hp in 6th gear at 60 mph I run 1500 rpm, tranny will run depending on incline but averaging 212-215 tranny temp
Shift down to 5th I run 1700 at 60 with same variable’s tranny temp drops up to 10 degree’s
I’ve read that the C12s on this board love low rpms.
To me traveling at Ca  “60”speeds put me into which is better a little higher rpm and cooler tranny or lower rpm and higher tranny temps.
At higher speeds I imagine tranny temp may drop while in 6th find out in a few days. When I get to kick it up.
Thanks

[Steve Huber]

Michael,
I'll let the C12 owners opine on best RPM. When I drive in CA with the 55 MPH speed limit, I find it difficult to maintain 6th gear at less than about 63. To get from 5th to 6th I need to run up to about 63-64MPH and then back off to 60 MPH. Then I notice it will drop to 5th very easily; slight incline, wind gust, etc. Wondering if your tranny temps in 6th are partly caused by multiple shifts between 5 and 6. (This is with a C9 and Allison 3000 but seem to remember same issue with my C12 on a trip up I5). Also, the lower RPM results in the water pump running slower which also could contribute to what you are seeing.
Steve

[Michael Turnipseed]

Thanks Steve, my friends C12 425 shifts just as you described, mine doesn’t shift down until close to 50 mph while watching the Alladin.Also engine temp never above 190. I’m thinking unless over 61-2 keep 6 in my pocket but that’s why I thought some input from those with the experience would be helpful. Never been one to lug or sit in a shift zone but this 6th has some range.