Awesome guys! Thanks for the info. Would one transmission be better for a swap down the road if the Saginaw ever goes or are they about equally as strong and will need the same amount of stuff changed to work in the car? Heck I don’t even know if either of them are good or not. It would be kind of fun to try to rebuild one.
New guy with a 4 speed wagon
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By the '75 date code that is a SUPER T-10 so go buy a lottery ticket fast! That is the strongest of the bunch and the two rings makes it a 2:43 first gear. You multiply that by your rear ratio and you get the overall ratio. So in your case the 3:89 times the 2:43 gets you 9:45 which is pretty sweet for street use. To me 10:1 is the ideal and the closer you get the better. The 4:56 rear times 2:43 gets you 11:1 which is great for racing but on the street you get five feet and have to shift again. If the Saginaw has the 2:84 first then times that by the 3:89 and you get 11:1 again. Super easy take off from a stop then shift fast to second. The old 4:56 you had times the 2:84 gets you 12.9:1 and that is ridiculous. Starting in second gear is 9:1 and I'll bet that is what you were doing before you changed rears. So they are all fairly strong transmissions with the ST-10 being the best as far as parts availability. Once you ID all the ratios you can make your decisions. You want to know what you want to use the car for and then set up the ratios to work best for you. Read: https://www.hemmings.com/stories/article/borg-warner-t-10-four-speed
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Awesome info guys. Before I switched the 4.56 out I got it out of the garage, cleaned it off, clay barred it, and changed the plugs and oil and just took it out for a short cruise late at night. I didn’t care for driving down the road in 4th gear with the speedo buried probably only going 45-50mph and the engine wound up like it was. I can remember being 13 or 14 years old and my dad wanting to wait for the exhaust to cool back down to close the headers back up before leaving the race track but my brother and I thought it was the coolest sound in the world so he drove it 20 or so miles home. And that was with the stock rear. Me in the back seat grinning ear to ear. Not so much anymore.
Read: http://pontiacpower.org/BW.htm This is a simple chart but it's more complicated than that.
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