The best engine ever from GM: 472/500

[Denise 20352]

  Good point, and just one more reason to wonder what they were smoking when they came up with that differential.

-d

[Mike #19861]

 The theory at the time was that gasoline engines were more efficient at low speeds with larger throttle openings. It reduces the pumping losses. But GM already found out it does not work in the real world when they released that fleet of Police cars back in 69 with the 260 hp 2-bbl 396 and a 2.56 gear. They found that in real world conditions, they were actually worse because the officers were flooring the cars to get decent acceleration. The result was fuel economy that barely ever broke into the double digits.

  Mike

[Andrew 10642]

Can a different differential be easily substituted to give more spritely acceleration and therefore, better fuel economy?

[Mike#19861]

As far as I know it is the same diff used in the wagons and police cars. The police cars have ratios of 3.08 or 3.23. Wagons also have a 3.08 gear. This would help a lot.

 I have driven a couple of 77/78 Cadillacs that could easily peel rubber. No doubt they had a shorter rear. They had plenty of acceleration. My dads 77 Fleetwood was a dog by comparison.

 Mike

[Andrew 10642]

Whats involved with switching a differential over to another version for 77-79 RWD Devilles?

[Michael Stamps 19507]

From what others have said it is pretty much a bolt in from other GM corp cars.

Stampie

[Denise 20352]

  You want to replace the differential anyway, because it will be full of metal shavings.

-d