Joined: Jun 2018

Posts: 554

My project is going well for my 72 and im reaching a spot where I need to see if this is a doable decision im thinking about

• Current Motor and trans is 350/TH350/8.5 inch 10 bolt rear - will be swapping in a 455/Th400
  • My 455 is not fully built yet (may not get there till Mach/April) - gotta keep wife off my back on spending too much money
  • I have a TH400 I got out of a 69 Firebird and just sent it off for a bench rebuild at a really great shop
  • I just sourced a used Driveshaft from a fellow forum member it was from a 455/Th400 car - so a "direct bolt on" for my prescription mentioned above
  • I have a 3.73 posi 12 bolt rear end from a 69 GTO my coworker is giving me
• My question is this:
  • My current TH350 trans is leaking all over the place and I do not want to even think about fixing it.
  • Can I pair up my new TH400 (once I move the cross member back) and the driveshaft I sourced, with the new 12 bolt rear end?
    • This gets me closer to my 455 swap as well
    • I know I will need the various TH400 item such as the longer trans cooler lines, the kick down switch, etc

I just want to know if I can take this step now of the trans, driveshaft, and rear with the existing rocket 350..I know with the 455 motor its a no brainer.

Thanks for taking the time
Brian

Joined: Apr 2011

Posts: 1,962

From: Nor Cal

Joined: Jun 2018

Posts: 554

Joined: Feb 2013

Posts: 15,394

From: Phoenix, AZ

Joined: Jun 2011

Posts: 6,657

I think the answer is yes, but we don't know what 455/400 car the DS came from. For example I assume it was another olds a body, but idk if for example the 72 w 455/400 and 10 bolt corporate rear driveshaft is the same as say a 70 455/400 w a 12 bolt Chevy rear ( Canadian car) or o type rear ( us car) driveshaft. In short we need more info I do know if it was from a big car w 455/400 it's likely to long

Joined: Jun 2018

Posts: 554

Actually the driveshaft I sourced came out of a 71 442 with a 455/TH400.

Joined: Feb 2013

Posts: 15,394

From: Phoenix, AZ

Joined: Jun 2018

Posts: 554

Well I can still use my original 8 1/2 inch 10 bolt. Since my buddy is giving me this 12 bolt I still need put some money into it to get it overhauled. I wonder if it’s just worth the money for me to swap out the gears in my 8.5 10 bolt to the 3.73 posi??.....is that pretty straight forward ? If so then I should be able to do exactly what I want for now , Rocket 350 paired to TH400 with the driveshaft mated to my 8.5 10 bolt. And when I finish my 455 then all I’m doing is a motor swap

Joined: Jun 2011

Posts: 6,657