4l80e w/205 in my 77 K20

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Tom Lexa

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Hey all, I'm new to the site....I have a 77 K20 with a sb400 and am looking to swap in an overdrive transmission.... I kinda want to put in a 4l80e w a 205 Case...but am not sure how much of a pain it would be....any advice would be great...thanks
 

Honky Kong jr

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Hey all, I'm new to the site....I have a 77 K20 with a sb400 and am looking to swap in an overdrive transmission.... I kinda want to put in a 4l80e w a 205 Case...but am not sure how much of a pain it would be....any advice would be great...thanks
Between the electronics to run it and the adapter needed and new drive shafts usually deters folks from doing it but if the price of that stuff don't bother you it's not horrible. And welcome to the site.
 

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One solution for the vss sensor on the transfer case is actually not installing one. 4l80e has two vss sensors, input and output. Output one can be used instead of vss in the transfer case. For the low range to work, then you just have to put a switch to feed output vss through a frequency divider circuit to imitate transfer case vss. Atmega chips have clock that can be manipulated to do it making an arduino board an easy choice.
 
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Honky Kong jr

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One solution for the vss sensor on the transfer case is actually not installing one. 4l80e has two vss sensors, input and output. Output one can be used instead of vss in the transfer case. For the low range to work, then you just have to put a switch to feed output vss through a frequency divider circuit to imitate transfer case vss. Atmega chips have clock that can be manipulated to do it making an arduino boars an easy choice.
I knew someone would chime in with fancy words and a low buck solution.:waytogo:
 

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That word makes my brain glitch and shut down. I have no idea why.
 

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I like the idea of a 205 behind 480...
Manual valve body.
This would be a cinch 'cause all my years driving (41, with a license) I have used D in autos. Meaning
I manually shift autos.
And speedometer? There are available servo driven cables to retro fit our speedometers but
like $400 or something stupid.
 

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Use a gps speedo
 

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90-91 spedo cluster, stand alone controller from 91-94 diesel gm truck, and can still get away with even simpler solution for low range shifting by disabling auto shift completely in low range and using two switches for manual shift. Or retrofit vss to transfer case or deal with signal electonically or build/buy converter.
 

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Also, 87-89 firebirds used factory mechanical to digital vss conversion
 

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