What does it take to put an 8.5 into a 7.5 car?

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pontiacgp

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Mar 31, 2006
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the other thing is to get an old shaft cut and balanced is only about $80 cheaper than getting a new shaft using your old yokes. When you get your shaft back after it's balance make sure you mark the front yoke so if you ever remove the u joint you don't put it back on out of phase.
 
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Turbo Zach

Comic Book Super Hero
Sep 8, 2015
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I got the guy I bought mine from to throw the GN drive shaft in the deal. I replaced the u joints with good brand name ones. When my car starts making power I plan to have a cromemolly shaft made. I would not trust factory very far! As for the swap. Direct swap.only thing was the 8.5 came with metric studs and the Monte had standard.
 

64nailhead

Goat Herder
Dec 1, 2014
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I believe 80 was the cutoff from standard to metric, but lugnuts are cheap - lol.
 

oldsmobile joe

Royal Smart Person
Nov 12, 2015
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Direct swap.only thing was the 8.5 came with metric studs and the Monte had standard.
you can always replace the front rotors with ones that have metric studs in them. cheaper than buying metric studs.
joe
 
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pagrunt

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Sep 14, 2014
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Elderton, Pa
For the lug nuts remember A bodys have inch studs ('78-'81) & G bodys have metric studs ('82-'88). This way you'll know what rotors to match the rear end axles. Side note, you '78 owners would need to swap in '79 up spindles or go with the Blazer conversion for metric studs.
 

84GP455

G-Body Guru
Jun 19, 2007
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Methuen Ma.
For my swap 7.5 to GN 8.5 it was fairly easy I did have to cut the shaft 1 inch but that's because I also swapped the th400 for the GN th2004-R as far as the 8,5 goes.. the best ones are out of the Grand Nationals and 442
 

oldsmobile joe

Royal Smart Person
Nov 12, 2015
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