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So in my mad quest to figure out wether or not I can retain my stock TH400 when I put my 4.3 v-6 has possibly come to an end. I was told that the jeepster TH400 was a BOC transmission. This frustrated me because I found an adapter by JEGS for a BOP transmission to a Chevrolet engine. So I called and talked to four transmission shops and they said that the BOC and the BOP are on and the same. So the adapter will work or so I hope. Hope this helps someone else in their engine quest.

 

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Just to get you straight. BOC & BOP are two different animals. I don't give a rat's behind what the tranny shop told you.


The BOC cased TH-400 was called "round-top" and was made in the early 60's, while the BOP cased TH-400 was called "twin-ears" and was made to fit the later 60's engines. Your Jeepster's 225 engine was made to fit a BOP tranny, ("twin-ears"). You have the older design BOC TH-400, ("round-top"). Jeep took care of this by adding an adapter between the 225 engine and BOC TH-400.

So now you want to use a Chevy engine without getting a Chevy cased tranny. The only way to do this is add a second adapter. You will then have the Chevy engine attached to a chevy to BOP adapter, attached to the BOP to BOC adapter, attached to the BOC TH-400.


This should now be clear as mud.
 

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I'm certainly not knowledgable of the auto trannys, but -
I was at a friend's shop talking about round top vs twin ears. He showed me a 400 that had BOTH bolt patterns! He said they were fairly limited production, so scarce, but he tried to keep several around since they fit most anything.

Seems like if someone was going to switch guts that would be the one to use.

He's out of business now, but I can call him at home to find out what they were from if need be.
 
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