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1969-70 3/4 Ton Gmc 2wd 6cyl Swap To 8cyl

bandit2804

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bandit2804 New Member

bandit2804

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hello i just purchased a gmc 2wd step side truck the 6 cyl engine was worn and tired i have several small block s and decided on putting in a 283......i have everything need ed ---except that when doing the engine swap i notice the 4 speed trans was further back than the smallblock was-------not to be confusing but there is a approx a four inch difference where the engine(smallblock) is now gonna sit--------so i have figure that i will have to move the 4 speed a head approx four inches-------that leaves me scratching my head and not very good at math my question ---does anyone know the correct diveshaft length i now need-----???????? this is my first post here so if i did something wrong im sorry-----bandit
Stevens03 Senior Enthusiast

Stevens03

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Welcome to the site. Relocating the transmission cross member I think would be pretty easy and any drive shaft place would tell you how to measure for a new one. But heres a quick link to help :jester:
[url="http://www.ehow.com/how_5914608_measure-driveshaft.html"]http://www.ehow.com/how_5914608_measure-driveshaft.html[/url]

And welcome to the site.

bandit2804 New Member

bandit2804

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[quote name='Stevens11' post='1209016' date='Oct 10 2011, 01:05 PM']Welcome to the site. Relocating the transmission cross member I think would be pretty easy and any drive shaft place would tell you how to measure for a new one. But heres a quick link to help :jester:
[url="http://www.ehow.com/how_5914608_measure-driveshaft.html"]http://www.ehow.com/how_5914608_measure-driveshaft.html[/url]

And welcome to the site.[/quote]
thank you i have both motors pulled and im pretty sure ill need your guys help along the way in the next few days ill keep ya posted peace !

grampadirt Senior Enthusiast

grampadirt

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First off,welcome to GMT :)

My son has the same truck you have(except his is a fleetside).It has a 327 with a TH400 tranny so I can't help you in the driveshaft area.If you have a pick-a-part in your area you might get lucky and find a driveshaft to fit your truck.IIRC the frame has a few bolt holes for the crossmember to accomodate different tranny lengths.

doverarjim Senior Enthusiast

doverarjim

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Posted

Welcome first off. Did you change the motor mounts to the small block ones? I think that they moved the engine back to meet the transmission. I am going off of memory and that can be a problem. But I have done this before a long time ago and I know that we did not do anything to the transmission or drive shaft. I also think that we had to get a fan shroud because of the motor being moved back from the raditor. :)

grampadirt Senior Enthusiast

grampadirt

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Posted
Been thinking about this the last few days...I'm pretty sure you have the mechanical clutch linkage and having that means the ''idle lever shaft assembly'' is not moveable as the frame end is riveted to the frame.So,the engine end of the shaft has to line up with that.Have you tried to re-install this assembly?

I think Jim's right,the tranny stays where it is and engine is moved to match the clutch linkage. Also,look to see if there are other motor mount holes in the frame to accomodate the V8.Not a bad idea to replace the mounts anyway.

Does the assembly where the clutch fork adjusting rod attaches look like this?
[img]http://i461.photobucket.com/albums/qq340/grampadirt/69%20Chevy/scan.jpg[/img]

Look at the motor mount,there is another hole in the frame,maybe for a different engine
(my son's '69 with a 327)
[img]http://i461.photobucket.com/albums/qq340/grampadirt/69%20Chevy/DSC02228.jpg[/img]

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