Front differential ratio ID

[east302]

I decided to change the rear diff fluid in my son’s newly purchased 98 K1500 and see that the ring gear has 12:41 stamped on it. Crap. The glovebox tag says it’s a GT4 (3.73).

Is there any number or stamp on the front differential that identifies the ratio? The only thing I see is what looks like a GM part number stamped on the right axle but I’m not finding a connection.

Assuming that one of the previous owners didn’t change the front gears, is the least expensive option to just swap the whole rear axle from a salvage yard?

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[b454rat]

I don't know how to tell the ratio for the front without tearing it apart or rotating it and doing the math. Double check the RPO tag that it's for YOUR truck. I've seen where someone swapped glove box doors. But I'd think it be easier to swap the rear than a front. Last time I pulled a front was for an SAS....

 

[east302]

Thanks. Yeah, I was hopeful that the glovebox was swapped but the VIN on the label matches.

 

[mtl111]

You beat me to checking the vin on the rpo tag. 12:41 should be 12 tooth pinion and 41 tooth ring gear or 3.42. The front diff should have a GM sticker on top with a part number, can't guarantee that it will show what the ratio is when you look it up.

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[b454rat]

Prolly grenade lock grenad'd, rather than rebuild or put in a new carrier, just replace whole axle.

 

[mtl111]

The paint on the ring gear looks like something a salvage yard would do.

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[east302]

You beat me to checking the vin on the rpo tag. 12:41 should be 12 tooth pinion and 41 tooth ring gear or 3.42. The front diff should have a GM sticker on top with a part number, can't guarantee that it will show what the ratio is when you look it up.

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I looked on the top with a mirror, didn’t see any sticker. Just what appears to be a part number for the casing.

Human nature dictates that someone grabbed a junkyard rear axle without checking the ratio and threw it on. I can’t see anyone going to the trouble to swap front and rear from 3.73 to a 3.42.

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[east302]

The paint on the ring gear looks like something a salvage yard would do.

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Good point. I saw it but quickly forgot it once I did the math on those numbers/ratio.

 

[mtl111]

I parted out a rollover 99' 2 door Tahoe w/76k miles awhile back to save the parts, not sell. The front diff is 3.73 and has the GM sticker on top, unfortunately I don't have a pic right now. Just trying to come up with an easier way to verify the front is still 3.73 in your truck.

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[east302]

Is this a G80?

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