Rear end Swap ?

[54blackhornet]

Can anyone ID this rear, and can I put it under a 71 K -10 ? Guy said it is out of a 86 1/2 ton, also comes with front D44 thanks, is it a 10 bolt ? Should I wait for a 12 bolt ? Truck will not be off road !

[cdngearhead]

It's a 8.5" ten bolt, just as strong as a 12 bolt and way cheaper to Posi and gear swap

[54blackhornet]

Thanks for the information ! I am glad, it already has posi in it ! Perches and shock mounts are different then 12 bolt ?

[Ol Blue K20]

Perches should be the same. One shock mount will be correct the other won't. The71 mounts both pointed towards the front. Later years they're staggered.

[starvinartis]

Perches on 1/2 ton 86 k models are 42.25" center to center. Pre 73 k models are 40.25"

[54blackhornet]

Can you change a 71 K10 frame to later style shock set up ? Frame is bare right now so anything I can do to improve it, now is the time. I picked up both front and rear axels from a low mileage 86 K10, front axel was almost never in gaged ! $300.00 for both.....

[starvinartis]

Another thing to consider, does the gear ratio of this 10 bolt match the ratio of your front axle? Or are you swapping out both? Still safe to check that the new set is a match if you're swapping both. Seen a few trucks with mismatched ratios. Further, what transmission are you running? Visible in pic is what appears to be a 208 TC, most commonly mated to 700r4, those transmissions work best with 3:73 ratios, 3:42 and 3:08 gears cause it to take longer to shift into overdrive.

[Ol Blue K20]

Originally Posted by 54blackhornet

Can you change a 71 K10 frame to later style shock set up ? Frame is bare right now so anything I can do to improve it, now is the time. I picked up both front and rear axels from a low mileage 86 K10, front axel was almost never in gaged ! $300.00 for both.....

I'm sure you can move the upper mount. I thought they changed the perch width after the square body....

[starvinartis]

Ha ha you posted while I was typing. Since you will have to move the leaf spring perches on the 86 axle, I would move the shock mounts on the axle too, rather than changing frame mounts.

[54blackhornet]

Both of my original axels are junk so I am swapping both from the 86, 373 with posi in back. After pricing new parts to rebuild the old 12 bolt I feel I did OK ? Going to use the original 205 TC out of the 71. The one in photo is out of the guys 86 I got the axels from. Thanks for the input .....

[starvinartis]

Originally Posted by 54blackhornet

Can anyone ID this rear, and can I put it under a 71 K -10 ? Guy said it is out of a 86 1/2 ton, also comes with front D44 thanks, is it a 10 bolt ? Should I wait for a 12 bolt ? Truck will not be off road !

Originally Posted by Ol Blue K20

I'm sure you can move the upper mount. I thought they changed the perch width after the square body....

Leaf spring spacing ( distance between perch pads )
67-87 two wheel drive half ton leaf spring are all 42.25
67-72 k-10, 20, and 30 are 40.25
73-87 k-10 are 42.25
73-87 k-20, 30 are 40.25 as are the two wheel drive 30's. The only one I'm not sure ( memory issues ) are the 67-87 two wheel drive 20's (3/4 ton)

[starvinartis]

Originally Posted by 54blackhornet

Both of my original axels are junk so I am swapping both from the 86, 373 with posi in back. After pricing new parts to rebuild the old 12 bolt I feel I did OK ? Going to use the original 205 TC out of the 71. The one in photo is out of the guys 86 I got the axels from. Thanks for the input .....

I agree you got a good deal. Out here just the rear axle can bring $300. Your driveshafts will probably need to be lengthened BTW, or at least the rear one. The 12 bolt is a bigger pumpkin and comes further forward than changing the corporate. Also the u-joint size may be different. Hate to rain on the parade but I'm just pointing out the issues I've encountered over 30 years of building old Chevy trucks. Good luck and enjoy!

[caseyt28]

Whats a common rear end everyone is using when goin from a 6 lug to a 5 lug? And a disc with posi? Ive looked and looked and cant seem to find any answers.....can someone help

[starvinartis]

Originally Posted by caseyt28

Whats a common rear end everyone is using when goin frrear to a 5 lug? And a disc with posi? Ive looked and looked and cant seem to find any answers.....can someone help

When changing 63-70 to 5 lug I try to use 71-72 stuff. Just my preference. 70 rear diffs with the big brake drums will accept 71-72 five lug axles.There are plenty of after-market sites that sell disc brake conversion kits for any of these axles.

[caseyt28]

Im lookin for a stout rear end for the fact im building upa 5.3 with a turbo set up Nd gonna be bagged and body dropped on 24s

[54blackhornet]

The driveshaft from the transfer case to rear axel has a yoke that slides back and forth, will this make up for shaft length difference ?

[starvinartis]

Originally Posted by 54blackhornet

The driveshaft from the tran to rear axel has a yoke that slides back and forth, will this make up for shaft length difference ?

I don't think it will because at curb weight that slip yoke needs to be in the center of it's travel. Extending it to compensate will cause it to bottom out as suspension travels while driving. I just did a walk-thru of my yard to take a measurement but I have no 10 bolts. Plenty of 12's tho. Seems like the 10's wear out/break more than the 12's. We can't keep the 10's they go so quick. And they have those cheap a** guv-lock posi's or a tensile "s" shaped piece of steel that simply puts pressure on the spider gears. Give me a clutch type 12 bolt posi anytime over those. But if its a daily driver never off road and you don't lift it or go with oversize tires it should last a while. And you thought this would be easy and cheap? Just kidding.

[starvinartis]

Originally Posted by caseyt28

Im lookin for a stout rear end for the fact im building upa 5.3 with a turbo set up Nd gonna be bagged and body dropped on 24s

In the 90's some Silverado's came with a six lug 14 bolt non floater, and some even have factory disc brakes. This would be a stout rear that you could have axles relaunched for 5 lug or simply buy after market 6 lug rotors for the front. And of course there's the always popular Ford 9 inch or even Dana 60 & 70

Sorry my phone puts in words it deems fit regardless of what I type. Repunched instead of relaunched

[caseyt28]

Originally Posted by starvinartis

In the 90's some Silverado's came with a six lug 14 bolt non floater, and some even have factory disc brakes. This would be a stout rear that you could have axles relaunched for 5 lug or simply buy after market 6 lug rotors for the front. And of course there's the always popular Ford 9 inch or even Dana 60 & 70

Sorry my phone puts in words it deems fit regardless of what I type. Repunched instead of relaunched

Thanks for the info. Much appreciated

[54blackhornet]

I think I will start with the front axel first ? Thanks guys ? How can a 10 be so weak ? GM thought it was good enough for a truck ?