Need a GM 12-bolt for a 1971 K5

[Morris75]

I picked up a '71 K5 and it needs some rear end work. The pinion is sloppy and probably needs bearings, crush sleeve and pinion seal. I'm on a ridiculous budget so I"m wondering if it's cheaper to buy a complete used 12-bolt and swap it in. What years do I need to look for that would have all the same dimensions including shock mounts, etc. and still be a 3.08 ratio. I know 12-bolts came on everything but I want to find one that is the cleanest and most direct swap.

What years and vehicles should match what I have now?

Thanks.

 

[6872xtc]

The only years that are a direct bolt in, are '67-'72. I don't remember if the '67 was for sure 12 bolt. I bet that you are going to have a difficult time finding one in good shape due to age. I have one in unknown condition laying out back because it came out of a '72. But it needs a yoke at minimum, probably more.
If you can move spring perches, then there are more years to look into.

 

[TuckerK5]

I picked up a '71 K5 and it needs some rear end work. The pinion is sloppy and probably needs bearings, crush sleeve and pinion seal. I'm on a ridiculous budget so I"m wondering if it's cheaper to buy a complete used 12-bolt and swap it in. What years do I need to look for that would have all the same dimensions including shock mounts, etc. and still be a 3.08 ratio. I know 12-bolts came on everything but I want to find one that is the cleanest and most direct swap.

What years and vehicles should match what I have now?

Thanks.

I will have one available within the next year maybe 6 months but that’s the best I can do right now. Don’t know condition except that it does roll.

 

[Morris75]

The only years that are a direct bolt in, are '67-'72. I don't remember if the '67 was for sure 12 bolt. I bet that you are going to have a difficult time finding one in good shape due to age. I have one in unknown condition laying out back because it came out of a '72. But it needs a yoke at minimum, probably more.
If you can move spring perches, then there are more years to look into.

Thanks! Will the ones from pickups between 67 and 72 fit directly or only Blazers?

 

[diesel4me]

A '68-72 4x4 pickup 1/2 ton "should" be the same,a salvage yard with a Hollander interchange manual or software can verify that--be aware a 2wd pickup those years often had coil springs ,so those wont be a bolt in swap,the shock mounts might not be the same either,but can be modified..

 

[6872xtc]

2wd is 5 lug wheels. Not sure about overall width compared to 4x4, so would the inner axles swap?

But yes, trucks have the same axles.

 

[diesel4me]

I know someone who swapped 6 lug axle shafts into a 2wd '67 or '68 C-10 and they fit and worked OK...so maybe the 4x4 ones are the same length ..but I'd check further to be sure..

 

[TuckerK5]

I know someone who swapped 6 lug axle shafts into a 2wd '67 or '68 C-10 and they fit and worked OK...so maybe the 4x4 ones are the same length ..but I'd check further to be sure..

I drove a 67 C10 in high school (1986) and it was a 2wd and had 6 lug wheels. Pretty sure 1/2 ton 2wd had 6 lugs up until some year.
I bet @ktmoutfront knows.

 

[6872xtc]

I drove a 67 C10 in high school (1986) and it was a 2wd and had 6 lug wheels. Pretty sure 1/2 ton 2wd had 6 lugs up until some year.
I bet @ktmoutfront knows.

'70 was the last year for 6 lug 2wd. When the front got disc brakes, they changed lug count. So '71 started the 5 lug , 1/2 ton 2wd.
I tried converting a '68 C10 to 5 lug rear in '85, the axles were a different length.

 

[diesel4me]

Your right ,now that I think about it,even the early G-10 vans up until '71 had 6 lug wheels also...from the 40's or even earlier ,Chevy had the same 6 lug bolt pattern on all its cars and 1/2 ton trucks..

I remember finding some wire spoked ancient 6 lug rims in the woods behind a friends house many years ago and for the heck of it I tried putting them on my '56 3100 series pickup and they fit!..first time I dumped the clutch they twisted the spokes like macaroni..his dad was mad,I found out they were from his fathers old chevy coupe from the 30's and the rims were worth quite a bit...oops....we just thought someone dumped them there..

My friends '68 or '69 C-10 had a 5 lug rear end in it ,not sure if it was swapped in or what..he wanted to put 6 lug rally wheels on it that he had with nice tires ,without using wheel adapters...he got 6 lug drums off a salvage yard truck that fit on the front no problem..