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Discussion Starter #1
I have a 1975 nova custom 2 door coupe with a 350 I built with my dad. I’m putting out about 380 hp but am having trouble putting it to the road because I have the stock open diff still in the car. Does anyone know of any budget diff kits or rear end swaps that I could do so I can put power down with both tires instead of these one wheel squealers :D
 

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You can buy a mini spool on eBay for about $60 bucks. Not the perfect situation for a daily driver but like not having powering steering, you will get used to it.
 

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Scrap yard

Go to one,if your car has an 8.5 diff (most of them do) get a posi from another 8.5 diff with the correct axle spline and,swap your gear set &away you go.
:yes:
 

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Go to one,if your car has an 8.5 diff (most of them do) get a posi from another 8.5 diff with the correct axle spline and,swap your gear set &away you go.
:yes:
I was considering this as an option. I have just never done much of anything related to diff’s and did not know if the guts of the 8.5’s were different from car to car and year to year. Do you know if all GM 8.5’s are compatible with each other or do i need to look for a specific vehicle/ year that has the 8.5 Posi?
 

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You can buy a mini spool on eBay for about $60 bucks. Not the perfect situation for a daily driver but like not having powering steering, you will get used to it.
Won’t this cause a lot of hopping in turns/parking lots?
 

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I was considering this as an option. I have just never done much of anything related to diff’s and did not know if the guts of the 8.5’s were different from car to car and year to year. Do you know if all GM 8.5’s are compatible with each other or do i need to look for a specific vehicle/ year that has the 8.5 Posi?
They are compatible with each other provided the axle spline count is the same. 8.5 from a 1/2 ton with the same spline count as yours will work, be wary of the Gov Loc Posi , try and find a posi from a mid 70's GM car. A spool on the street is not a good idea,:turn::turn::turn:.Everyone is afraid of rear end work,don't be. The internet is full of info.
 

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Spools are not that bad on the street. I would not want to put up with it as a daily driver... but for a fun fast hot rod on a dry road.... great!!!
 

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8.5 Rear Diff.

I was considering this as an option. I have just never done much of anything related to diff’s and did not know if the guts of the 8.5’s were different from car to car and year to year. Do you know if all GM 8.5’s are compatible with each other or do i need to look for a specific vehicle/ year that has the 8.5 Posi?
You need to know that the carriers are listed as "series "--like 2--3--meaning that a 2:73 ratio carrier cannot use a 4:10 ratio ring gear without using a 1/4 " spacer plate . Also as stated above the axle spline count 28---32 whatever must match yours. You can do it---folks here will help with info. The absolute easiest would be a whole rear end with a posi from the 70s. Swap the carrier & use your ring gear.
 

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You need to know that the carriers are listed as "series "--like 2--3--meaning that a 2:73 ratio carrier cannot use a 4:10 ratio ring gear without using a 1/4 " spacer plate . Also as stated above the axle spline count 28---32 whatever must match yours. You can do it---folks here will help with info. The absolute easiest would be a whole rear end with a posi from the 70s. Swap the carrier & use your ring gear.
Actually for the 8.5" the 2.73 does use the same carrier as 4.10.

Carrier split is 2.41-2.56 is a 2 series carrier, 2.73-5.13 is a 3 series carrier.

Miles
 

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8.5 Rear Diff.

This comment piqued my interest as rear diff stuff is the only automotive thing I currently refuse to touch. Any good websites us beginners should look at for GM stuff?
Go on YouTube ---choose a good quality video on G.M. Rear diff. overhaul for your ring gear 10--12 bolt.
 

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If you do it yourself, make sure you have the proper tools. Magnetic base dial indicator, vernier caliper, inch pound torque wrench, and a healthy impact gun.
 

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Discussion Starter #14
Actually for the 8.5" the 2.73 does use the same carrier as 4.10.

Carrier split is 2.41-2.56 is a 2 series carrier, 2.73-5.13 is a 3 series carrier.

Miles
I hate to be the rookie but I’m really new to this. Does this mean that i wouldn’t be able to get a Posi differential from a gm 8.5 with a 4.10 and keep my stock axles? Would it be as simple as taking axles from the donor vehicle and rebuild with those or is it more in depth?
 
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