GM 8.75 parts searching L74 455 speed parts???...

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Old August 3rd, 2019, 01:15 AM
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GM 8.75 parts searching L74 455 speed parts???...

Hi my name is Chris I have a 76 Delta 88, with a for 480632, 8.75 10 bolt. Factory 2.56 open diff....

Does anyone out there know of any aftermarket posi units and or ring and pinions for these Axel's, also I'm running a factory non-adjustable quadrajet and would like some suggestions on swapping it for something better and adjustable?

My car is a bone stock l74 1976 vintage. So all the smog stuff and factory air cleaner are I'll still on it.

Plus I would like some suggestions as well as to performance upgrades for the motor I know these things were smogged almost to death, especially being the last year of the 455. So I'm curious as to what is out there that I can put on this thing without tearing into the bottom end.

Any and all suggestions are welcome and thank you for allowing me to be on this form with you wonderful people

Last edited by 1976L74delta88; August 3rd, 2019 at 01:18 AM.
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Old August 3rd, 2019, 04:33 AM
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welcome to the site .monzaz on this site will have the answers on your differential .as far as your motor goes it all comes down to to the power level your looking for and your budget.i also had a bone stock 455 in my cutlass supreme it ran very good but lacked the power i expected.i can tell you what i did made a huge improvement without touching the bottom end, but still nowhere near the power the 455 is capable of .we changed out the j -heads for a set of e-heads with bigger valves and matching springs added a slightly bigger cam with new lifters ,cloyes double roller timing chain ,edelbrock aluminum intake ,thornton w/z manifolds and a pypes dual exhaust kit .all this in the 3000 dollar range.the biggest problem imo is the deep dish pistons and very low compression . i most likely lost some compression on my engine by going from the factory .017 head gasket to fel pro .040 and only took .010 off the heads.getting back to the rear, my car has a 2:56 posi in it and i absolutely love driving it on the highway. it still has no problem roasting the tires .if you just recently got your car .drive as is and enjoy it for a while
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Old August 3rd, 2019, 01:46 PM
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Thanks man oh, did you use stock heads or did you use aftermarket aluminum heads?, And what carb and cam combo an intake did you use if you don't mind me asking????
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Old August 5th, 2019, 06:30 AM
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1971 -1976 Rear end 8.875 (Pontiac rear)

Originally Posted by 1976L74delta88
Hi my name is Chris I have a 76 Delta 88, with a for 480632, 8.75 10 bolt. Factory 2.56 open diff....

Does anyone out there know of any aftermarket posi units and or ring and pinions for these Axel's, also I'm running a factory non-adjustable quadrajet and would like some suggestions on swapping it for something better and adjustable?

My car is a bone stock l74 1976 vintage. So all the smog stuff and factory air cleaner are I'll still on it.

Plus I would like some suggestions as well as to performance upgrades for the motor I know these things were smogged almost to death, especially being the last year of the 455. So I'm curious as to what is out there that I can put on this thing without tearing into the bottom end.

Any and all suggestions are welcome and thank you for allowing me to be on this form with you wonderful people
No Aftermarket Posi units for this rear. There still should be some pretty good selection of used posi unit that we have clutches to aid



in making them grip again if needed.
Gears - only 3.55 was available a few year ago BUT the company that made them changed hands and we are all waiting to see if they will produce them or not?
They mount on the 3 series (mid series posi 2.73 carrier)
Bearings and seals etc are all available for rebuilding what you have.

IF you are keeping the stock gears and want to switch to posi I could possible have a few more on the shelf here also.

Along with rebuild kit Axle bearing kit etc.
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Old August 5th, 2019, 07:37 AM
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8.875 fullsize posi

I have several of the eaton posi units for fullsize cars.I rebuild and blueprint posi units as well. Feel free to call 518-234-2480 I'm in upstate NY.

Last edited by SmirchIs#1; August 5th, 2019 at 07:40 AM.
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Old August 5th, 2019, 07:46 AM
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Old August 5th, 2019, 09:09 AM
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3.55 posi?

Thanks again to all you gentlemen who arehelping me out.do you have a 3.55and a posi that you're willing to part with and how much are you willing to part with it for?
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