Final ratio with th400 in 3rd gear
02-18-2011, 11:51 PM
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Final ratio with th400 in 3rd gear Whats the actual ratio in 3rd gear with a th400? Ive been told they are 1.1 and been told there not. Thanks for any input you guys have....
02-19-2011, 07:40 AM
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Any three speed gm trans the 3rd gear ratio is 1:1. In a power glide which is a two speed is 1:1. In a gm 4 speed over drive unit 3rd gear is 1:1. The only trans that does not have a 1:1 ratio I believe is the 6 speed auto.
11-22-2013, 08:09 AM
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Buzzbomb I have a TH400 that was behind a 4.3 V6. I now run a 350 V8 and found the final ratio of the TH400 and found that the V6's used a lower ratio. I have 2:73 gears and it drives like a 4:11. Mileage is about 11 MPG.
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11-22-2013, 09:22 AM
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but you have a non locking converter, so the engine RPM will seem like the ratio isn't 1:1 if you do the math.....I just wonder if thats where the confusion could be coming from..
11-30-2013, 04:11 PM
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The 3rd gear ratio is still 1-1 , I have never seen a 4.3 with a 400 behind it from the factory . Don't think it ever happened ! What is this combo in ?
12-02-2017, 09:14 PM
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12-11-2017, 09:23 PM
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Not technically a TH400, They were TH375's.....Which are based on the TH400 but with a 27 spline output & fewer frictions. By the mid 80's TH350C production had ceased but GM still offered a 3 speed auto & was probably cheaper than a 700R4.
