Differential Carrier change?

[Rakkasan]

Well I’m into the drivetrain part of my rebuild and fell into some disappointment. Started with the front since it’s more expensive. GM Corporate 10 bolt.

‘79 k10 that assumed had 3.73 gears in it only to find the’re 3.08. My intention is to run a 6” lift with 35s and might have gotten away with the 3.73s but now there’s no way. I’m going to have to run lower gears.

Since I’m changing might as well go with what I wanted. 4.56.

Question: Do I need a new carrier since I’m dropping so low compared to the 3.08?

Any help would be great.

Thanks

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[Rakkasan]

‘O yeah. Not to mention the PO let the axle seals go what seems like 20yrs ago so there a little surface rust on the carrier and the gear oil was thicker than molasses in winter.

 

[Derrick]

@HotRodPC do you know
@Old77

 

[HotRodPC]

Yep, I know Old77, he's another one of the moderators here.

 

[Derrick]

Yep, I know Old77, he's another one of the moderators here.

lol, I meant did you know if he needs a different carrier for the gears he wants my computer did some weird stuff and I did not know till I posted it that I looked like do you know this guy I was just getting your attention to see if you could help the guy out.

 

[Rakkasan]

Any help would be great.

 

[Rakkasan]

So I’ve been searching the inner webs all day and starting to get conflicting info. At least in my mind.

I’ve read that you can run 4.56 on the stock 10 bolt carrier that had factory 3.08s in the front but on a 12 rear you have to step up to another carrier.

Any different insight out there

 

[HotRodPC]

So I’ve been searching the inner webs all day and starting to get conflicting info. At least in my mind.

I’ve read that you can run 4.56 on the stock 10 bolt carrier that had factory 3.08s in the front but on a 12 rear you have to step up to another carrier.

Any different insight out there

I think that is correct, I'd have to look myself to make sure. IIRC, the break on the 10 bolt is in the 2.XX, anything 3.XX on up is all good, but I think the cut off on 12 bolt is 3.08 and down, and 3.23 on up. It just matters where the break is for that specific rear end. Now some rear ends you can get Thick gears to make them work after the break point, but you can't get skinnier gears to go the other direction.

 

[HotRodPC]

According to ringandpinion, it does appear to be correct. You can keep the 10 bolt carrier and go with 4.56's, on the rear, the breaking point is 3.73 so if you have 3.08's in the 12 bolt, then you need the 3.73 and up carrier.

Is it possible you have a 3.73 rear axle already? If so, just put 3.73's in the front axle. Or if you already 3.73 carrier in the 12 bolt, it too will go 4.56 and just buy gears your carriers should be fine.

 

[Rakkasan]

According to ringandpinion, it does appear to be correct. You can keep the 10 bolt carrier and go with 4.56's, on the rear, the breaking point is 3.73 so if you have 3.08's in the 12 bolt, then you need the 3.73 and up carrier.

Is it possible you have a 3.73 rear axle already? If so, just put 3.73's in the front axle. Or if you already 3.73 carrier in the 12 bolt, it too will go 4.56 and just buy gears your carriers should be fine.

Thanks for the reply

I wouldn’t think you could run different gears from front to rear. Am I wrong?

 

[HotRodPC]

You shouldn't but some people do. Mudders do it all the time, rock crawlers better not do it, and certainly not the street either.

Mudders will sometimes want faster RPMs on the front tires than the rear, or un a smaller steer tire from the back tires, and will use gear ratio compensate. I've seen many street 4x4's with off gears. A guy has 3.08's tears up his rear end and buys the first rear end he can find for $100 and it happened to be 3.42, or 3.73, so they are out there. Don't assume anything if you just acquired the truck.

 

[rpcraft]

Here is a breakdown on the axle type and the carrier breakdown. Might be helpful

I think he's kinda boned but I can not recall which way the deep cut gears work. I think it is a possibility if you have the three series carrier on a 10 bolt you can use a thick ring gear for 4 series gear, but not vice versa... Don't hold my feet to the fire on that though.

http://www.differentials.com/technical-help-2/carrier-breaks/

 

[rpcraft]

Or, all the front 10 bolts diffs use the same carrier from 3.08 to 4.56.

 

[rpcraft]

No carrier break for 10 bolts according to the fine fellows at Pirate 4 x 4.. YMMV, lol.

 

[HotRodPC]

No carrier break for 10 bolts according to the fine fellows at Pirate 4 x 4.. YMMV, lol.

Not true. It could be true for them cuz none of them are going to be running in the 2's as in 2.73 or 2.56, but I'm 99% certain you're correct, 3.08 on up numerically, or 2.73 and down which leaves only 2.56 or 2.57 that I'm aware of. So if you have a 2.73 or 2.56 ratio you pretty much have **** all around and you will be buying a new carrier. Being it's that odd, I wouldn't even consider seeing it a thick gear is possible, just replace it. And yep, there are several 2.73's out there and even in 4x4.