In his email Don Slaney is complaining of poor mileage in OD when towing his
baby home. What may be happening is that the load on the Caprice is not
sufficient to cause it to downshift to drive but is close to the limit.
This is resulting in a little more foot throttle to keep things going and
thusly having a negative effect on the vacuum and therefore on the economy.
When in Drive the engine is more capable of pulling due to the increase in
RPM and also probably better slotting in the power band therefore better
vacuum and mileage. I know with my F--- R----- pick up with V6 and 5 speed
I run into a similar problem when towing especially if the load is a little
heavier or the wind on the highway comes up. Usually results in
downshifting to 4th gear better RPM, more power and better economy.
Hope this info is useful
52 Chev 1300
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