[Chester Stone]

Forest, I recently experienced significant mountains on I-5 in Southern Oregon and Northern California with long and extended grades. I decided to ignore the RPM and speed gauges and focus on the boost gauge. The transmission did a good job of downshifting and I tried to keep the boost below the maximum which is 27.5 to 28 lbs. The boost air is the cause of most of the engine heat buildup, and keeping the boost at about 20 lbs. resulted in the engine never having excessive temperature. Speed and RPM were of no concern going up, but came into play going down the mountains. The transmission increased its heat going down hill using the Jake, and reached 135 degrees. I was relieved when I discovered that the transmission top temperature should not exceed 150 degrees. So in answer to your RPM question, I suggest the boost gauge is more important the RPMs.