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71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pictures

10K views 74 replies 10 participants last post by  Portagee 
#1 ·
Hi All,

Wanted to post some pictures and descriptions of my automatic to manual transmission conversion in my 1971 Chevelle, in case it was useful. This process should be roughly the same for all 68-72 GM A-bodies, but YMMV.

I'm going to gloss over the TH350 removal, as it is pretty straightforward, and focus more on the issues relating to stuffing the T56 Magnum into the car.

So the plan is to cut the tunnel out, insert larger patch with opening for shifter, design custom center console to fit over new transmission tunnel, then reinstall.


Here's the victim: 1971 Chevelle with a Dart 427ci SBC, 12 bolt rear, truetrac diff with 4.11's, aftermarket front and rear suspension from SC&C.
 
#70 ·
With everything under the car buttoned up, I needed to address the issue with the bellhousing to oil drain plug interference. Decided to just mark to the location with a marker, and go for it by hand with a drill and bimetal hole saw. It actually came out much better than expected. Did the same thing to the engine block plate, and ended up perfect. FYI, used a 1-1/4" bi metal hole saw, which gave plenty of room around the circumference of the oil drain plug to get a socket on there without having to fight anything.
 

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#71 ·
And FINALLY, what we've all been waiting for, a fully installed T56 Magnum in a '71 chevelle. Took a ton of work, but I am SUPER happy with how it all came out.

(sorry about the pictures rotating again, annoying, I know....)

Now to start work on the shifter service plate/box for the interior. Mocked this up out of cardboard for now, and plan to use my new sheet metal brake to bend this into shape. Will also need to do some welding to get the flanges for mounting to the actual tunnel. The plan is to use riv-nuts around the perimeter of the opening, with gasket material between the tunnel and the service box, so that it will be easily removed for addressing any potential issues (or upgrades) down the road.

I'll continue to update this thread as I make (slow) progress on that front...
 

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#72 ·
Looks awesome! Just wait until you drive it :)

I will be starting to repair my tunnel this weekend(never got around to it since I was having fun driving it and it wasn't as much surgery as yours! I guess I should replace the carpet while I am at it, it is dirty and I am not super happy with it. I wonder how hard it would be to carpet it myself.
 
#73 ·
I replaced the carpet in mine, and it was really easy. I just laid the carpet out in the sun for a couple hours, then sprayed the floor and the back of the carpet with 3M spray adhesive. Wait for it to tack up then lay it down. Ordered the carpet from Rock Auto - awesome price, and it was really nice quality.
 
#75 ·
Adding a few more progress pics. Not Technically part of the trans install, but part of finishing everything up related to the install to get her back on the road!

Made a mounting plate that I riveted to the new trans tunnel and on the firewall. Made a nice location for all of the electrical accessories, and a new fuse block.

Also working on the center console. Just cardboard right now, but fits great.
 

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