Modern Tranny in a 1969 GTO - Pontiac GTO Forum
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post #1 of 9 (permalink) Old 05-15-2011, 10:32 PM Thread Starter
 
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Modern Tranny in a 1969 GTO

My GTO has a th400 in it. I'd like to put a modern automatic tranny in it.
electronics aside, whats the best choice to mate to a Pontiac 400?
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post #2 of 9 (permalink) Old 05-16-2011, 09:45 AM
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Although not equipped with overdrive, the 1969 TH400 is far superior in strength, durability, and design over any "modern" tranny. It's a better unit. I assume you want overdrive..... Any overdrive unit you swap in will be inferior in strength, but can be made to handle the job with upgrades. Common choices are 200r4, 700r4, and 4L60E, to name a few. From what I understand, the 200r4 is the easiest swap, a basic "bolt-in". Some of the others require you to become a member of the Floorpan Cutters Association of America.
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post #3 of 9 (permalink) Old 05-16-2011, 09:48 AM
 
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A well built 200r4 is the easiest and best swap. I THINK, the 700r4 only comes in a chevy bolt pattern and will require an adaptor plate....E



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post #4 of 9 (permalink) Old 05-16-2011, 09:51 AM
 
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Jeff, I recently became a member of the FPC of A club !.....4l80e with a set back engine = sawsall+welder.....



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post #5 of 9 (permalink) Old 05-16-2011, 12:08 PM
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Eric, I'll say what you've already said : you're going to hell.......You're also a charter member to HCAOA, too. Hood Cutters Association of America. Seriously, you're doing your '67 proud. Can't wait until it's done!!
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post #6 of 9 (permalink) Old 05-16-2011, 01:43 PM
 
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Thanks .....that was only a LeMans hood...I saved the GTO hood for the afterlife!



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post #7 of 9 (permalink) Old 05-17-2011, 10:35 AM
 
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i just bought a 700r4 from monster transmission. i have a 400 with edelbrock heads comp cam and all the goodies. the tranny is rated for 600/hp and 600tqu. everything you will need to convert to a 4speed from a 3 speed. $2300 for everything even fluid. didnt install yet but so far happy with there service.
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post #8 of 9 (permalink) Old 05-17-2011, 11:28 AM
 
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I have a rebuild kit, a beast sun shell, a couple servos, and an adapter plate to stick a 700R4 behind a 455. It is also getting a constant pressure valve body so the TV cable isnt so critical. Should be enough to handle the 500ftlbs and tame the 3.42 gears. The swap to a 700R4 is a bit more involved than the 2004R, but still not that difficult.

The big changes to a 2004R from a Th400 is the driveshaft yoke has to be a longer one the size of the Th350 yoke (if it isnt long enough it wont seat in the rear case bushing causing problems) cooler lines, and moving the trans crossmember back a couple inches. My 70 has the 2004R in it right now, it got hurt behind the 455, but then again it was just a core out of a junkyard that I didnt even bother to put a rebuild kit in.
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post #9 of 9 (permalink) Old 05-17-2011, 04:16 PM
 
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Quote:
Originally Posted by Joust View Post
My GTO has a th400 in it. I'd like to put a modern automatic tranny in it.
electronics aside, whats the best choice to mate to a Pontiac 400?
Which rear gears are in the car now?



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