Auto Parts: GM 3.42 GU6 Rear Axle, pep boys, gear ratios

Question
I'm trying to figure out if a GU6 is a GU6 if the gear ratios are the same, but the ring sizes can be different? Does this make a difference?

For example, There are S10s with GU6s but the ring sizes are 7.65, mine is a 8.5, but I have a 1990 k1500 4x4 w/a 5.7l and I need a rear diff?

So if the gear ratio is the same, will it work?

Thanks.

Answer
Hi Marc,

No. the ring gear size also changes the pinion size.

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Thanks for the question, I hope this information was helpful to you.
Fred
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