Which transmission fits my coupe ?

472viper

Member
Oct 17, 2019
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Sioux Falls SD
64.5 coupe with 170 6 cylinder. Pretty sure it is a c4 behind it and the transmission is getting weak. Slips badly in first gear until it is good and warm. I am searching for a core that I can rebuild and am not sure what to look for. Are 6 cyl and V8 transmissions different ? Are there bolt patterns I need to watch for ? I have a line on a 6 cyl with automatic transmission out of a Comet but the guy doesn't know what year it was. Says it has been laying in his shop for 20 years, never got around to doing anything with it. How do I tell C3 from C4 ? Any other things I should look for ? Thanks so much for any insight.
 
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rbohm

SN Certified Technician
Apr 12, 2002
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tucson,az
the only differences between the V8 and six cylinder C4s are the number of clutches in each clutch pack in the trans. the six cylinder C4s can be upgraded to V8 specs if you want easily. also the accumulator piston is different as well. as far as i know the C3 never came behind the inline six.
 

wicked93gs

10 Year Member
Sep 30, 2006
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Nashville TN
There is a bellhousing bolt pattern difference between 1965 and 1966 though, which is why 66-68 200CI blocks are double pattern drilled:



This article is really about mtx bellhousings, but you can at least compare the different bolt patterns(mainly different up top) so you know what your bolt pattern SHOULD look like.
 

472viper

Member
Oct 17, 2019
57
5
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66
Sioux Falls SD
All good info there. I am concerned C4 automatics bolting to a 170 6 cylinder. Actually I am going to pick up a 170 6 and c4 combination tomorrow. Supposedly came out of a Comet of unknown year. I might just end up with a spare (rebuildable) engine !