| GMC Driving fundamentals question [message #293882] |
Fri, 15 January 2016 09:50  |
jknezek
Messages: 1057
Registered: December 2007
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For years I have manually downshifted my GMC when necessary. I find this happens in primarily two cases: 1) when pulling a long slope and the engine drops below 40 mph (roughly) in 3rd gear and 2) in town driving when I have to slow for a stoplight or traffic and end up at slowest between 30 and 40 mph. I have a Manny Tranny, so no kickdown switch.
However, for the holidays my loving wife purchased a vacuum gauge and a tach for me to install. Rather than using the speedo, I wonder for those of you with a tachometer when you choose to manually downshift. When does it become lugging in a higher gear?
Other important information, I have a 3.55 final drive and, as far as I can tell, the original 455 that came with the coach.
Thanks,
Jeremy Knezek
1976 Glenbrook
Birmingham, AL
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