Rear end interchange

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Rear end interchange

Postby dakafire » Tue Mar 14, 2017 3:38 pm

I just recently purchased a 2002 s10 crew and the previous owner was a complete idiot. they replaced the passenger rear axle but did not put the wheel bearing back in (believe it or not). Now i have to replace the rear end in the truck and am looking for information on what vehicles GM put the rear end into. It is a 3.42 ratio, with 8 1/2 ring size opt gu6 4x4. Any help with this will be GREATLY appreciated!
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Re: Rear end interchange

Postby LoneWolf04 » Tue Mar 14, 2017 5:03 pm

I would double check what rear end you have. If indeed it is a gu6, then it is not an 8.5" it'll be a 7.5" or 7.6" in the late 90s. If you have an 8.5" ring gear you'll want to verify the ratio, it's possible someone swapped in a zr2 rear end and front diff. Only the zr2 trucks/blazers came with 8.5" rear ends and all had 3.73 gearing.
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Re: Rear end interchange

Postby dakafire » Wed Mar 15, 2017 8:33 am

I actually called the dealership with my vin and verified it is a gu6 8 1/2 from the factory. It was rare but they did offer it as an option without zr5. I have opened the case and verified it is an 8 1/2 ring gear. That's why this is becoming a nightmare to find. I was just hoping that they used that rear end in other vehicles other than the crew cab S10.
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Re: Rear end interchange

Postby LoneWolf04 » Wed Mar 15, 2017 1:36 pm

If you've got an 8.5" with 3.42 gearing you will want to rebuild it. Finding another one will be a needle in a haystack. You could always find a standard 4x4 (7.6") rear with 3.42s. That's an easier solution if your heart isn't set on keeping the 8.5" rear. There were quiet a few later years that came with 3.73 gearing like mine though so you'll have to verify gearing in one. Honestly that gearing is a lot nicer for towing and gives the truck a better feel. If you're ambitious might be worth finding a wrecked zr2 and swap both front and rear diffs out.
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Re: Rear end interchange

Postby JaVeRo » Wed Mar 22, 2017 9:22 am

If you still have the differential open, count the teeth on the pinion. There should be 41 on the ring gear and 10, 11, or 12 on the pinion.
12 teeth is 3.42 - 41/12=3.416666
11 teeth is 3.73 - 41/11=3.727272
10 teeth is 4.10 - 41/10=4.100000
2001 S10 Crew (wife's mail truck)
2002 S10 Crew, 2003 S10 Blazer
2006 K2500 5 speed
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