390-400 swap

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Dec 13, 2010 | 07:00 PM

mytybug

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390-400 swap

I have a 76 crew 4x4 with a shot 390 and a 78 crew 2 wheel with a brand new 400 and it is my parts truck (78 crew). I have the 4x4 pan for the 400. What needs to be done for this swap?

Dec 13, 2010 | 07:19 PM

hairyboxnoogle

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Swap the tranny with the 400, and motor mount towers, should be about it.

Dec 13, 2010 | 08:21 PM

mytybug

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Quote:

Originally Posted by hairyboxnoogle

Swap the tranny with the 400, and motor mount towers, should be about it.

Thank you for your help

Dec 13, 2010 | 08:40 PM

Bullitt390

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And be prepared to go straight to hell!

just kidding...

Josh

Dec 14, 2010 | 12:18 AM

Atwiss

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From: Rushville, NE

yeah i did the exact same but got the 400 from a ltd all we did was get a bell housing modified the engine mounts and mine is a manual so we had a little trouble with the z bar but i cant remember what we did

Dec 14, 2010 | 07:11 AM

hairyboxnoogle

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Not sure if you will have to change the tailshaft and housing, that would be something you would have to measure. The tailshaft is like the first thing to go into a tranny case, so if it needs to be swapped, she has to come completely apart. Good time and oportunity for a rebuild and a shift kit ($145). Yours is the divorced T-case, and i think they used the short tail shafts like the later 2wd vans, and im thinkin the 2wd truck has the long shaft.

Dec 14, 2010 | 09:42 AM

mytybug

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i have a 77 high boy as well that had a 460 in it originally a 360 truck. Motor is gone but rest of drive line is still there. Could I use that tranny to make it easier. I don't want to mess around with tearin down a tranny. Would rather shorten or lengthen the intermediate shaft. Or just use this frame for my rebuild, for it is mint.

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Mar 4, 2011 | 10:54 PM

phays

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i have read alot about doing this. i am currently do a 390 to 400 swap. Ive had a 1976 f150 ranger XLT4x4 4 speed with the 390. i just recently bought a 78 f250 3/4 ton 2 wheel drive 4 speed with a 400. i took the 400 and put it in the 76 i just took the bell-housing and put it on the 4 speed in the 76. the only thing i ran into was the motor mounts to fit!!!!! so i unbolted the mounts from the truck moved them back (toward the cab) 2 inches drilled where the new bolt holes needed and weld where i could not drill holes. other than that, thats all you might think about if you have a manual trans.

hope this works for someone as it did for me!