bought a new rear end and have some questions

[Squareforceone]

So I bought a 12 bolt rear end out of a 80 k10 for my 84 c10. New rear end is a 12 bolt posi 3.73 6 lug. Old rear end was an open rear end 10 bolt 5 lug. I want to run the 12 bolt with 5 lug axles I know I will need shafts from a factory 5 lug 12 bolt. I think my brakes will all swap over. So my question is what else do I need to change to make this work I heard there was a different u-joint? Anything else? Also this is a budget built do you think a junk yard would sell me just axle shafts? If so what trucks should i look for with 5 lug 12 bolts if any? Thanks

[77K10Silverado]

A pull-a-part type place should sell them. They will sell anything. If the rear brakes are drums, you will have to use the 5 hole drum. Not sure about the u-joint. others my chime in. I just rebuilt my 12 bolt with G80 locker. Might want to look at my thread to see pics. I'd suggest replacing all the bearings and seals while you have it off and torn down! I went the extra mile and powder coated the whole thing. Done!

[kevinr1970]

I don't know about 12 bolts, but on 10 bolts the shock mounts are different from C to K.
Probably not a problem if stock height, but if lowering it will start to be a problem depending on how low you go.

[RIDE-RED 350r]

Last summer I blew my 12-bolt out in my 78 K-10 so bad that the diff housing even got cracked. It was a factory 6-lugger.

I bought a complete 12-bolt, 5-lugger from a friend and rebuilt it. My 6-lug axles went right in with no issues so you shouldn't have any issues that I am aware of if you source some 5-lug axles out of a 12-bolt axle assembly.

I cannot speak to the yoke as to interchangeability between your old 10-bolt and the new 12-bolt as my new axle was the same as the old one that blew and I used the best of the pair I had. If the 12-bolt yoke does not match the U-joint in your driveshaft you should be able to take the yoke and old joint to a parts shop and get a joint that fits the 12-bolt yoke on 1 axis and your driveshaft on the other axis.

And I concur, since you are swapping axles, spend the extra few bucks on a set of wheel end axle bearings and seals. Pretty inexpensive peace of mind there.

Wish I hadn't scrapped those 12-bolt, 5-lug axles... I could have hooked you up. But that was part of the deal with my friend..he gave me a better than fair price for the axle I got from him on the condition he got my old core and all the other parts I didn't use so he could scrap them....

And might I suggest that if you find a junk yard who has a 12-bolt truck axle, might be smart to just buy the whole thing. I was surprised that I could not find one single gm 12-bolt truck axle in any junk yards within 150 miles of me here in NYS! With all the tens of millions of them made, I couldn't believe that nobody had any! 10-bolts everywhere... I got super lucky my friend had been kind of a square body chevy truck/parts hoarder.. I got the only one he had.

[bmchevy1979]

If you have the bigger u-joint on your driveline you can get a conversion u-joint to hook up to smaller yoke on 12bolt or get yoke that accepts bigger u-joint. 10bolts came with both sizes 1310 and 1330(has a bigger span but same caps as 1310) so measure across yoke in between tabs that center and hold u joint to see if they are the same