Quote:
Originally Posted by JLBIII
Currently have 2.56 gears and Saf-T-Trak rear un my 68 FB with 400HO and TH 400. I'm looking at replacing gears and carrier to either 3.36 or 3.55 and the correct posi unit. Plan to eventually put in an OD. Which would be the better street gears for the 400HO engine? Thanks
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My '67 GTO convertible with a standard 400 and TH400 trans came with a 3.36 rear gear and it was decent all-around. I do a lot of long distance high speed driving, so about 15 years ago swapped in a 2.56 rear that had safe-t-track. With the 3.36, I got about 15-16 mpg at a steady 65 mph and the comfortable cruise was about 70 mph. The 2.56 gives me 21 mpg at about 80 mph, and 23 mpg at 65. 3000 rpm is a tick over 90 mph. So for me, the 2.56 was an 'upgrade'. Not as strong off the line, but still burns two tires. Ideally, for me, an A or F body with a TH400 would be perfect with a 2.93-3.08-3.23 rear gear. Pontiacs don't need a steep gear to get going like small block Chevys do. It all depends on the type of driving you do. If I just did short trips on back roads, I wouldn't of changed the 3.36 out. But I do cross-country trips and enjoy the increased MPG, decreased running temps, and almost no noise at high speeds.