71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pictures - Chevelle Tech
Transmission & Driveline Transmissions and Differentials

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post #1 of 48 (permalink) Old Nov 5th, 19, 3:59 PM Thread Starter
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71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pictures

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.
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post #2 of 48 (permalink) Old Nov 5th, 19, 4:01 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

https://imgur.com/eJmrGza

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post #3 of 48 (permalink) Old Nov 5th, 19, 4:03 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

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post #4 of 48 (permalink) Old Nov 5th, 19, 4:18 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

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post #5 of 48 (permalink) Old Nov 5th, 19, 4:20 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Tired old TH350 waiting to be removed:
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post #6 of 48 (permalink) Old Nov 5th, 19, 4:21 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

I'm going to try to link an Imgur gallery to this post, but it doesn't seem to want to preview the pictures in the actual post - anyone have any tips, let me know.

https://imgur.com/gallery/Kffb6LJ
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post #7 of 48 (permalink) Old Nov 5th, 19, 4:38 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Started with a conservative cut to see where the trans wanted to sit, then marked the outline of the patch, and a dotted cut line ~1.5" inside of that (orange lines)
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post #8 of 48 (permalink) Old Nov 5th, 19, 4:39 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Tunnel cut out
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post #9 of 48 (permalink) Old Nov 5th, 19, 4:41 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Got this patch panel from a guy on ebay - fit over the area perfectly! Was shipped to me flat, so I just bear hugged it around a pole until it was generally in the right shape, then I bent the edges of the floor at the solid orange line up to mate with the face of the tunnel patch. Seems like it's going to work well.

(not sure why the image rotated sideways)
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post #10 of 48 (permalink) Old Nov 5th, 19, 4:42 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Been waiting a long time to see this! T56 fits perfectly in the opening.
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post #11 of 48 (permalink) Old Nov 5th, 19, 4:44 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Cut an ugly hole for the shifter to pop through - will clean that up later.

(image rotated again for some reason)
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post #12 of 48 (permalink) Old Nov 5th, 19, 4:53 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

View from underneath.
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post #13 of 48 (permalink) Old Nov 5th, 19, 6:50 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

In the meantime, I've also been working on the design for the new center console. Feedback and suggestions definitely appreciated, as I've never made one before.

Plan is to wrap the black surfaces in black microsuede to match the corbeau seats, and the grey faces on the top and around the shifter/buttons in a black madrid grain leather to match the dash.
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post #14 of 48 (permalink) Old Nov 6th, 19, 9:29 AM
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Excellent work! Looks like the patch panel couldn't have worked out any better.

1971 Chevelle SS454, T56 Magnum 6 speed, 3.31 Posi

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post #15 of 48 (permalink) Old Nov 6th, 19, 1:55 PM Thread Starter
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Re: 71 Chevelle TH350 to T56 Magnum Conversion: Step-by-step with pict

Thanks, Chris. You're right - the tunnel patch was spot on. Although I needed to extend the shifter opening farther back than I would've liked to allow the rear shift rail to clear (since the patch set so low there).

But I checked out your T56 install, and I had been thinking about doing the same thing with a shifter access box to cover the hole and seal around the shifter. Your car looks awesome!
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