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Discussion Starter #1
Can anyone tell me how many splines are on the oem 8.5 & 8.6 rear ends. I hear 28 in some places and 30 in another.
I don't know and can't find it. I know someone here is sitting on correct answer.
Thanks guys,
Ron
 

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Old Fart
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I think it depends on year and application the newer ones are 30 spline I think but I'm no expert. There are others on here that know more specifics than I do but if you are doing a V8 swap you definitely want 30.
 

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Gears and Differentials
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As far as I know all 8.5 and 8.6 GM corporate rear ends had 30 spline axles after '90. The S series 8.5 might have been an exception. The 8.5 was upgraded to 8.6 in '99 and all of them should have 30 spline axles.
 

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Been there Done it
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The only replacements I can find for 94-97 ZR2 list them as 30.
 

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Discussion Starter #7
I just bought 3:42 from 99 Blazer 2dr, 4.3, 5 spd. RPO tag didn't say G80 though. I'm going to try to pull cover tomorrow, and see if I'm going to have to buy posi or not. I'll count while I'm there and make sure what it is. Buy of century though, 100.00. I guess it being 5 spd v6 made it 8.5.
 

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Old Fart
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I just bought 3:42 from 99 Blazer 2dr, 4.3, 5 spd. RPO tag didn't say G80 though. I'm going to try to pull cover tomorrow, and see if I'm going to have to buy posi or not. I'll count while I'm there and make sure what it is. Buy of century though, 100.00. I guess it being 5 spd v6 made it 8.5.
Just don't waste your money on a Gov maybe it will lock, get a good aftermarket diff like a Detroit locker, TruTrac, or Eaton.
 

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I just bought 3:42 from 99 Blazer 2dr, 4.3, 5 spd. RPO tag didn't say G80 though. I'm going to try to pull cover tomorrow, and see if I'm going to have to buy posi or not. I'll count while I'm there and make sure what it is. Buy of century though, 100.00. I guess it being 5 spd v6 made it 8.5.
Sent you a text message.
Thanks, David
 
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