| Differential question for thought [message #263825] |
Thu, 09 October 2014 07:48  |
kerry pinkerton
Messages: 2565
Registered: July 2012
Location: Harvest, Al
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My 77 is a late model with the 403. Freshly rebuilt with Paterson carb and distributor, Manny tranny with PowerDrive and a 3:21. This gives a final drive ratio of 3.66. UNBELIEVABLE change over the original 3:07. Pulling my Saturn TOAD, I got 8.5 MPG on the recent 1900 miles to Wisconsin and back. On that trip, Ken Henderson was following us in his Caddy coach. Ken likes to run on his cruise control and I'm sure he was driven nuts by my speed changes since I don't have a cruise. I would hit the bottom of a big hill at 65 and be going slower at the top UNLESS I really got into the carb secondaries.
HOWEVER, I drive around 60-65 and the tach shows it's running just at 3000 RPM. This is right at the bottom of where the motor seems to want to run. While she pulls every hill we come to, I'm thinking that a cruising RPM around 3500 might make the motor happier and more responsive.
I doubt that I will do a differential change unless we decide to make some cross country jaunts but would like to hear from members who are running greater than 3:70s
Kerry Pinkerton - North Alabama
Had 5 over the years. Currently have a '06 Fleetwood Discovery 39L
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