Quote:
Originally Posted by Ramairnacho
I'm not sure why everyone knocks the 273 252 or 242 gears they where found in Trans am and formulas in the late 70 s and with those gears I think.gas mileage is better or am I wrong? But at end of day I might slap some 331 posi and scream down the freeway at normal speed limit getting 10 miles to the gal. Not!
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I do Not knock these ratios, and I own a very early 1971 2.73 rear, and a late 76 2.41 .
What OPH said was pretty much true though. A 2 series ( 8.75 ring gear) "Safe-T-Track" or "Posi"carrier for a 68-70 12 Bolt Chevy /Pontiac is a rare piece. Not reproduced. The open ones are around though.
In a 10 bolt ( '71 -81 for this conversation) you can use a 3 series carrier for a 2.73
gear ( have built a few myself), but NOT for a 2.56 or 2.41 . Also New carriers for these 8.5 rears are all over and some are inexpensive and have carbon fiber clutches vs steel.
If you want to use your TH400 and cruising and economy is paramount,
Call Franks Pontiac and grab a 2.41 Posi from a Firebird. With 15 inch 25 inch tall tires youll be at around 2500 at 72 mph ( a mere guess without any wind resistance). There are calculators to try online.
I happen to like Overdrive, and this is a pic of a car of mine with 3.42 gears,
26 inch tall tires ( 225/70/15 -- same as in 1979) and .67 OD .. taken on I-95 --- Th2004R transmission
