What Transmission do I have?

[JohnnyPopper]

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

[JohnnyPopper]

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.

[Mr Diesel]

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.