73-87chevytrucks.com
73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: JohnnyPopper on November 04, 2025, 07:48:45 pm
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I bought a TH400 from my buddy who has a truck recycling gig here. He said he drove the truck prior to parting it out, checked out.
I noticed when looking at it, that it had a 6 bolt TC. I noticed that all the Flex plates I worked with have 6 mounting holes, but only ever used 3.
Any clue on what this came out of? Are there better features than a standard TH400?
TIA
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Chat GPT is your friend.
Given your description (BBC engine + converter with 6 attachment pads + TH400 mention) I believe:
You probably have a heavy‐duty or aftermarket converter that uses a 6-bolt pad layout (possibly built for a TH400 or a TH400‐derived/4L80E application).
It is not a typical factory TH400 behind a BBC but rather an upgraded/modified unit.
The flexplate or converter may have been adapted/swapped for performance/drag use, hence the 6-bolt mounting.
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The 6 bolt TC were used on the 6.2 diesel. Supposedly heavier duty. Heard very mixed opinions about that though. Not sure if they had other applications too.