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81 TA auto to manual swap question


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9 replies to this topic

#1 gennaro

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Posted 09 December 2020 - 05:11 AM

Hello all  i've been doing a lot of research to swap out my auto to manual on my 81 TA. I have sourced out pretty much all the parts . The engine i have in it is 69 400 which i had in my GTO. The question is can I use the M21 with The the hurst shifter that came out of my 68 GTO or do i need a shifter specific to a firebird ? Also are there any other specific parts i need for the m21 install ? thx in advance 



#2 sea dog

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Posted 09 December 2020 - 05:52 AM

Since the shifter comes up through a hole in trans tunnel, most any shifter can be made to work. However, speaking from transmission swap experience, there may have to be a special bracket to use the gto shifter in your car.

 

One thing you will need to change would be the automatic ratio rear end in your 81 firebird. You should have rear gears in the 3:23 or 3"42 range. Late 70's birds with auto trans usually had rear gears in the 2:56 to 3"08 range

 

Also during that time period GM used a mechanical clutch linkage. This included several pieces, one of which was a bracket that had to be welded to the front frame. You need to get these parts and have someone who knows what he's doing, weld the bracket in. GM engine, at the time, had a threaded hole in engine block for linkage to bolt up to engine.



#3 b_hill_86

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Posted 09 December 2020 - 06:36 AM

Not to sound contradictory but having swapped my 77 from auto to manual, I imagine the gto shifter would work. An issue you might have is the shape of the shifter handle which could make for an uncomfortable reach. I replaced my factory shifter with a b&m that came with some parts. The handle is a different shape than the factory so it puts the shift knob a little it there away. Not a problem for me since I have longer arms but something to consider. I think the factory handles can be changed but dont quote me on that.

As far as the rear end ratio, its something to consider but I wouldnt say its something you NEED to change. I drove my car with a 2.41 after the 4 speed swap. Was it ideal? No but it was driveable. Ive since changed to a 3.08 which works just fine although yes, manual cars usually got 3.23+

Lastly as far as the bracket on the frame for the z-bar (also called a bellcrank I think) mine just bolted on. My frame had dimples in it where the holes were meant to go. I drilled and tapped them and bolted it on. Maybe in addition welding is preferred.

You didnt ask but one thing I just thought of was making sure your crank snout is drilled to accept a pilot bearing. I seem to recall being told some cranks arent.

Edited by b_hill_86, 09 December 2020 - 04:01 PM.


#4 JoePeek

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Posted 09 December 2020 - 02:36 PM

I did a auto to manual change in a 73 Formula years ago. The block was already tapped to screw in the ball on the block side of the Z-bar, and on the frame side, there was a plate with a slot in the top that bolted to the frame. The holes were already tapped in the frame as well. I got a factory Hurst shifter from a '76 TA that came up through the console in the correct location. Although the crank was for an automatic, the flange was machined to use a pilot bearing as well.


Edited by JoePeek, 09 December 2020 - 02:43 PM.


#5 sea dog

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Posted 09 December 2020 - 03:24 PM

My experience came with a C3 corvette. The frame on it had no provision for bolt on bracket for z bar. Engine had the threaded hole for other end of z bar. Crankshaft accepted pilot bearing with no problem.



#6 gennaro

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Posted 10 December 2020 - 05:03 AM

Thanks for all the replies , my engine has all the provisions for a manual as i had it im my GTO with a 4 speed . My rear end ratio is a 3.08. The only thing im not sure of is the holes in the frame for the countershaft frame bracket , im hoping there are some threaded holes there, i will have to have a look. 



#7 b_hill_86

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Posted 10 December 2020 - 01:01 PM

81s could be had with a 305 Chevy and a 4 speed right? Im betting the dimples will be there at least. You may have to drill and tap them but I bet theyre there.

#8 Huck369

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Posted 14 December 2020 - 07:20 AM

What is the difference in the drive shaft length from a Turbo 350 to a T-10  4-Speed?


Huck

1976 Formula Clone

1979 Formula Parts Car

1988 Subaru XT6 5-Speed

1992 Subaru SVX 5-Speed

2012 Subaru Forester

2015 Subaru Impreza

...and a few Motorcycles....


#9 b_hill_86

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Posted 14 December 2020 - 10:22 AM

I reused my driveshaft. Just needed to change the yolk. Ive heard (read) others changed theirs. I dont know the correct answer. I just know I havent seemed to have any issues with reusing mine.
  • Huck369 likes this

#10 Huck369

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Posted 15 December 2020 - 04:09 AM

I reused my driveshaft. Just needed to change the yolk. Ive heard (read) others changed theirs. I dont know the correct answer. I just know I havent seemed to have any issues with reusing mine.

That sounds good, hope to swap mine, and want to be sure to have everything I need, before I pull the auto out.


Huck

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1988 Subaru XT6 5-Speed

1992 Subaru SVX 5-Speed

2012 Subaru Forester

2015 Subaru Impreza

...and a few Motorcycles....





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