Originally Posted by cb_13
Lower load in 3rd gear compared to OD. Which results in more engine vacuum, since vacuum is inversely proportional to load.
Thanks. that makes sense! my ac blows out of the defroster vents as well under the slightest load so i must have a vaccum leak somewhere, though i dont believe those lines are shared between those two systems. i wonder if the air res. box is? i will check with a gauge to see if it is holding vaccum.