BB to SB 727 interchangeability

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Craig Burriss

Craig Burriss

FABO Gold Member
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Hey guys, I’m planning on finding a big block for my RamCharger in the coming months and am trying to figure out exactly how I want to do it.
It’s currently got an 81 318 and 4x4 727 that I just rebuilt in it. The transmission works flawlessly, but I’m not a fan of the 318 in this big truck. And please don’t try to convince me to stay with a small block, because I’m not going to.
If I found a late 70s motor home 440/727, I’m pretty sure the tail housing would fit, but would it be possible to take the 4x4 tail shaft, and possibly all of the guts out of my small block trans and swap them into the big block trans case?
My long term plan is to swap in an NV4500 or a TR4050 5 speed, so I don’t want to spend a bunch of money on a fancy BB 4x4 727 when I’m just going to remove it later on.
Thanks!
 
The innerds are mostly the same from SB to BB.... obviously different bell (case), as you know. The biggest problem comes when you try to mix different vintages, but if you stay with '78-on, you will likely be ok, as long as they are both NON-lockup type.
 
Instead of the coming headache when something doesn't work and you now have a bench full of parts....sell it now while it has value and buy what you need.
 
Yup you sure can. Post #3 kinda sums it up.
 
After a few months I am just about ready to do the swap. I got a 71 440 that I’m building and it came with a 2wd BB 727, I haven’t verified the year of the transmission, but it is a non lockup style, and the SB 4x4 trans that’s in the truck is a lockup style.
I’m going to be pulling the drivetrain out in a few days to try start Frankensteining something together. I’ll try to take pictures and document it here.
 
Definitely pick up the 727 rebuild and upgrade books currently available by Tom Hand and Carl Monroe. You can't go wrong once you have those in hand. HTH Lefty71
 
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