diff gear swap ?

[Dylan86]

Ok, i have a 12 bolt diff with .273s and posi out of an 83 chevy c10.... way to much power loss for me. i want to put 3.73 gears in it. i heard with this type of diff having that high of a ratio and switching to a lower ratio there is some sort of spacer i need for the crown gear? anyone heard of this or done this? any help would be great!

[83GMCK2500]

What you want to research is where the "carrier breaks" are.

HERE

[Dylan86]

thank you, so my deck height currently is 1.420″. And if i want to put in .373s it would be 1.943″. Where do i go from there? Do i just get a 0.523" spacer?

[Dylan86]

i cant find any info on people doing this online... nor' can i find any spacer parts? does that mean if i buy the .373 ring and pinion kit for a 12 bolt it should just go in? one of my friends tried to install 4.10s in pretty much the same diff... it did not line up he had to re-assemble it back to 2.73s....

[83GMCK2500]

You will need to change the carrier, I sent the link so you could ID what you had and what you needed...

http://www.ringpinion.com/DiffWizard.aspx <---they sell open carriers as well as traction devices. Since you're wanting to swap gears now is a SUPERB time to put in a traction device.

[Dylan86]

there is no way to just use a spacer?

[wilkin250r]

First off, just so we have our terminology straight, higher numbers equals lower gearing, but I'll reference the numbers. 4.56 is a higher number than 3.73.

To answer your question, you MIGHT be able to do it, but it's not a spacer. You use what is called a "thick gear set", and they are specifically designed to use a high-numeric gear set on a carrier from a low-numeric ratio.

However, you might not be able to find a 3.73 in a thick gear. It's much more common in the 4.56 and higher numbers, I don't know if any manufacturers make the thicker gears in the lower numbers because there just isn't enough demand for it. The vast majority of people are lifting their trucks with bigger tires, so they're gearing in the 4.56~5.38 range. There aren't a whole lot of people making a major gearing change up to 3.73 past a carrier break.

Even if somebody does make them, it might not be common enough to list on the website or keep in stock, I would actually make a phone call to someplace like Randys Ring and Pinion and talk to an expert about what you're trying to accomplish.

[Dylan86]

Its actually the other way around than what you described,my terminology is correct, the lower the diff ratio,the higher the engine will rev on the highway.The 3.73 gears are actually lower than 2.73 gears,not higher. The higher the number, the lower the ratio.

but thank you for your help, i will try contact a few auto parts places and see what they can come up with...

im guessing no-one on here has actually done this swap before?

[LONGHAIR]

I wouldn't spend a nickel on trying to get a Gov-lock to work.
GM couldn't do it, so why should anyone else?

No, seriously. I would use anything other than that. I would put money into removing it...not installing it.

[Dylan86]

I am not putting any money into the locker, just the ratio, the locker works for now, when it goes ill put money to that then....

Originally Posted by LONGHAIR

I wouldn't spend a nickel on trying to get a Gov-lock to work.
GM couldn't do it, so why should anyone else?

No, seriously. I would use anything other than that. I would put money into removing it...not installing it.

[rs74]

Have you posted your question over in the drivetrain section?

[DesertCat]

Richmond gear sells the 3.73 gear sets for the 3 series and 4 series carriers.

[derrickmanx1]

Originally Posted by DesertCat

Richmond gear sells the 3.73 gear sets for the 3 series and 4 series carriers.

x2 on richmond. You will need the seris 3 carrier.

[LONGHAIR]

Originally Posted by Dylan86

I am not putting any money into the locker, just the ratio, the locker works for now, when it goes ill put money to that then....

You would be putting money in....involving a "Gov-loc", but not into removing it. This is good money after bad parts, expecting to get into it again later. Coupled with the fact that it's a move to a lower ratio makes it worse.
These units are marginal a best. They are ok in completely stock vehicles when driven gently, meaning by someone who has no need for a traction device in the first place. This type of driver would never even know that it was back there.
But that is how people defend them. The "there are millions of them out there" defense is given. While this is true, it means nothing to the higher performance driver. Lower gears, power improvements, larger tires, heavier towing, aggressive driving all contribute to killing one of these things. More than one will take it out even quicker...
When one does fail it is catastrophic. It's not that it just quits working, like a slipping clutch. It' a major explosion and the grenaded pieces go through the gear teeth and into the bearings. I have personally rebuilt many rear axles after these failures. None of the internal parts survives. I have even seen one crack the housing.
Despite the word lock in the name, this is not a locking differential. It's nothing more than a clutch-type posi-traction that is self-adjusting so that it acts like an open differential most of the time.
Bottom line, I wouldn't spend any time or money in keeping a gov-loc.

[wilkin250r]

Originally Posted by Dylan86

Its actually the other way around than what you described,my terminology is correct, the lower the diff ratio,the higher the engine will rev on the highway.The 3.73 gears are actually lower than 2.73 gears,not higher. The higher the number, the lower the ratio.

Exactly. So when I say "higher", am I talking about higher number or higher gearing? Does lower equal higher or does higher mean higher? Heck, I can't even change it to "larger" because the bigger numbers
are actually physically smaller gears. I'm not sure which higher we're talking about.

I never said you were incorrect, I was just trying to define one way so were were both on the same page, but apparently we weren't.

I don't think you'll be able to use the Richmond Gear set. If you look at the deck height from the first link http://www.differentials.com/technic...carrier-breaks and you look at the Richmond Gear page for a 12-bolt rear here http://www.richmondgear.com/07Apdfs/page27.pdf , you can conclude that the deck height for "Carrier 3" would be 1.700", and deck height for carrier 4 is 1.943". They list a 3.73 gear set for either one, but you don't have either one. Yours is not listed.

In fact, in the small print below the list of available gear ratios, it says "Will not fit 2.56 & 2.73 carrier on 80-83 Truck and Blazer"

You can see, it is possible to bridge the gap beyond a carrier break, but your particular application isn't common enough for Richmond to make it.

[LONGHAIR]

Yeah, that's the 2 series carrier. They don't get mentioned often in the conversation because they get removed to go with lower gears.
Those 2.56s were a real treat in a 4x4 with a 700r4

[Dylan86]

Thanks for your help everyone!. putting all you have said, i think it would be allot easier to just go find a different rear end completely, one with a good locker, and series 3 or 4 carrier, it would solve all of my problems,,, so thanks! just one last question for you all.... will the driveshaft u-joint match up if i swap the whole diff out to a series 3 or 4? thanks

[wilkin250r]

Yes.

The reason for the carrier breaks is because as the gearing gets lower (higher numbers), the pinion gear gets smaller in diameter, so the ring gear must get thicker to take up the space. Eventually, it's financially better to produce a different carrier than to add more and more material to the ring gear.

But regardless of whether you have series 2, 3, or 4 carriers, gov-lock, posi or open, the pinion gear mounts the same on ALL sets, and the driveshaft flange or u-joint will mount to the pinion gear shaft.

The particular carrier you have or switch to won't change anything that is outside the differential housing.