transmission change

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Old July 23rd, 2018, 05:32 PM
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transmission change

I have a 1970 cutlass with the original 350 engine. I am changing transmissions from the 350 to a 700r4. I want to add a new flexplate. My question is what are the specifications for the flexplate I need to purchase? 166 tooth? 168 tooth? I need some advise.
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Old July 24th, 2018, 07:29 AM
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Originally Posted by Olds51
I have a 1970 cutlass with the original 350 engine. I am changing transmissions from the 350 to a 700r4. I want to add a new flexplate. My question is what are the specifications for the flexplate I need to purchase? 166 tooth? 168 tooth? I need some advise.

Why do you need a new flexplate?


In any case, every single RWD Olds V8 from 1964-1990 uses a 166 tooth flexplate, as do most FWD versions (only the 307s with the TH325/TH325L4) transmissions have a smaller flexplate). If the ad says 168 tooth, that's a Chevy flexplate and will not fit your motor. Also, every single Olds V8 is externally balanced from the factory, so unless you know that yours was custom rebalanced during a rebuild, you want an externally balanced flexplate.
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Old July 24th, 2018, 10:51 AM
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Also the flex plate has nothing to do with the transmission. As long as it bolts to the torque converter that matches the transmission.
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Old July 25th, 2018, 11:39 AM
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WOO-HOO! Finally caught Joe with a error, when was the last time that happened?!

The Diesel engines used a different flex plate, and matching starter. It’s much thicker, with a different tooth count. Not to mention the starter is massive compared to a gas part.

I ran ran into this on a diesel to gas conversion. The guy had swapped the original diesel flex plate on the 403 he was swapping, found out the gas starter won’t work, and the diesel starter woundint fit around the headers he wanted to use. The trans had to come out for a flexplate change.
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