<VV> Improving fuel economy FC PG

[Dale Dewald]

At 21:06 11/13/2011 -0500, Timothy Shortle wrote:

>Hi All, My question: Will installing  a 3.27 PG differential get me better 
>mileage on my '63 Rampside? I currently have 3.55. And I am referring to 
>driving long distances on the open road. Thanks all.

Hello Timothy,

Although I prefer manual transmissions I could perhaps provide some ideas 
to consider:

1) If the Corvair PG had a lock-up torque converter, then I think yes, the 
3.27 ratio would enable greater fuel economy.

2) The question is: Does the efficiency gained from reduced engine RPM at 
road speed exceed the loss of efficiency due to added converter slip from 
the higher torque load through the converter?  Simplified: Does the added 
engine efficiency only end up as additional heat in the transmission fluid?

3) If you did encounter a steep grade that you could no longer climb in 
DRIVE, could you comfortably climb it in LOW?  Our '65 Greenbrier with a 
3.27:1 axle and 4-speed will do 55 MPH in 3rd gear with the engine turning 
a manageable 3500 RPM.  The same set-up with a PG in LOW would have the 
engine turning 4400 RPM or more.

Dale Dewald
Hancock, MI