# Rear Gears, Transmission Combo



## olde-goat (Feb 1, 2009)

I have been trying to locate my receipt for a posi differential rebuild that I had done on my 65 GTO a few years back. This car is still in the final restoration phase and has not been driven. Looks like I have misplaced the bill and am trying to recall the gears that were installed. I seem to recall 2:78. Not sure if that combination exists, but would like to know if anyone has that combination. Also would that gear ratio work with a Turbo 400? I should mention that the car has a rebuilt 389 with Tripower. Thanks


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## geeteeohguy (Feb 2, 2008)

2.78 is a stock ratio, an excellent high speed, mpg, and cruising gear. It will work great with the TH400. I swapped out the 3.36 gear in my TH400-equipped '67 a couple of years back with a 2.56 gear, and I love the fuel economy and comfortable highway cruising. 75 mph is about 2450 rpm....and 3000 rpm is a tick over 90mph. With $4 fuel, it sure is nice.


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## olde-goat (Feb 1, 2009)

Thanks for the reply. Finally found my paper work and 2:78 is correct. I have been working on this project for so many years I have to rely on my bills to help recall what I had done on the internals.


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