12 bolt rear end help.

[71ChevyCheyenne]

Hi I have 1971 chevy c10 that im trying to put a new rear end into. The rear end in it right now is a limited slip 4.10 rear end that is shot. Today I picked up a posi 12 bolt from a 67-69 i think. The rear end i have is a 5 lug. The posi is 6. The width is about an inch apart. I was wondering if I could take the whole internals of the posi and swap it into the 5 lug (if the splines on the axles are the same). Any help would be greatly appreciated.

[nightrider388]

Yes they are same except 6 lug vs 5 lug. 5 lug was a little wider for the front disc brakes

[71ChevyCheyenne]

Originally Posted by nightrider388

Yes they are same except 6 lug vs 5 lug. 5 lug was a little wider for the front disc brakes

so I could swap the posi into my limited slip and use the 5 lug axle still if the splines are the same correct?

Thanks for the quick reply! also how do you identify 12 bolts as far as dana 60,50 etc?

[nightrider388]

The covers are the way i tell. You can also get numbers off the rear end. The rear will have gm stamps in a few places. 12 bolt gm.. Don't have a drain plug.

[nightrider388]

What are you calling posi...vs limited slip? Posi is a Eaton brand limited slip. Or you mean single traction differential. ?

[nightrider388]

Also, you can't just swap anything direct. It would need to be set up properly just like a new install.

[GASoline71]

The truck 12 bolt had 4 series carriers starting with the 3.73 gearsets. So if the posi-traction rear end you want to swap is not a 4 series you won't be able to use the 4.10 gears without a spacer.

Also most of these 40 year old stock posi-traction units will need new clutches and bearings...

"Posi-traction" is Chevrolet's name for limited slip. They are the exact same animal.

Gary

[71ChevyCheyenne]

Originally Posted by GASoline71

The truck 12 bolt had 4 series carriers starting with the 3.73 gearsets. So if the posi-traction rear end you want to swap is not a 4 series you won't be able to use the 4.10 gears without a spacer.

Also most of these 40 year old stock posi-traction units will need new clutches and bearings...

"Posi-traction" is Chevrolet's name for limited slip. They are the exact same animal.

Gary

My bad sorry I'm not good on the technical terms. I have a gm 12 bolt single traction in it right now with 4.11 gears. I found a posi-traction rear end in the junkyard that is a 12 bolt gm as well except it's a 6 lug mine is a 5 lug. Is it possible to switch the internals of the posi-traction into the rear end that has the single traction gears right now? That way I can use the 5 lug axles with the right width for my truck.
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[feller]

Not trying to hijack, but couldn't help just re-drill the lug pattern? It might not be the "right way" but I've heard of this being done.

[nightrider388]

The axles are the width difference. You can swap just the axles and not affect the rear end set up. When dealing with 50 year old parts, if the junk yard one hasn't been rebuilt, it will likely need bearings, seals etc. If you swap anything other than axles, it has to be set up by someone who knows how or you will ruin the gears.

[wbc409]

You could get your axles re drilled, but it might be close to just buy retrofit 5 lug axles to fit the other rearend. Check the gears and the posi unit to make sure they are still good.

[71ChevyCheyenne]

Originally Posted by nightrider388

The axles are the width difference. You can swap just the axles and not affect the rear end set up. When dealing with 50 year old parts, if the junk yard one hasn't been rebuilt, it will likely need bearings, seals etc. If you swap anything other than axles, it has to be set up by someone who knows how or you will ruin the gears.

The posi-traction was in a 6 cylinder truck and looks perfect. As far as setting up the rear end I have someone who's done multiple rear ends helping me so that's not an issue. The problem is the housing the posi traction is in the brakes are completely destroyed and in the 5 lug the brakes are nice. So I would prefer swapping the internals into the 5 lug if it's possible.
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[LongBeachC10]

Hey 71ChevyCheyenne, dont wanna hijack but would you consider selling the 6 lug axles? I have a 71 C10 with a 12 bolt rear but want to convert from 5 to 6. Good luck with the swap by the way😬
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[randy500]

Originally Posted by 71ChevyCheyenne

The posi-traction was in a 6 cylinder truck and looks perfect. As far as setting up the rear end I have someone who's done multiple rear ends helping me so that's not an issue. The problem is the housing the posi traction is in the brakes are completely destroyed and in the 5 lug the brakes are nice. So I would prefer swapping the internals into the 5 lug if it's possible.
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The carriers posi or not interchange between 12 bolt rear ends. You do need to set up the carrier properly in the housing when changing them or you will ruin the gears, it will be noisy, etc.

The brakes between 6 lug and 5 lug are the same, I think some wheel cylinders differ whether the brake line goes straight out or is angled. For that matter all GM truck 11 x 2 inch brakes are the same all the way into the early 1990's at least.

You can take the backing plate off complete after you remove the axle and it all interchanges. Or piece by piece with minor differences, if you change all the pieces it works too.

Essentially what differs on brakes in all brands, GM, Mopar, etc, Is the axle flange pattern for the housing and the space from that same housing to where the brake drum mounts, knows as brake spacing.

[71ChevyCheyenne]

Originally Posted by randy500

The carriers posi or not interchange between 12 bolt rear ends. You do need to set up the carrier properly in the housing when changing them or you will ruin the gears, it will be noisy, etc.

The brakes between 6 lug and 5 lug are the same, I think some wheel cylinders differ whether the brake line goes straight out or is angled. For that matter all GM truck 11 x 2 inch brakes are the same all the way into the early 1990's at least.

You can take the backing plate off complete after you remove the axle and it all interchanges. Or piece by piece with minor differences, if you change all the pieces it works too.

Essentially what differs on brakes in all brands, GM, Mopar, etc, Is the axle flange pattern for the housing and the space from that same housing to where the brake drum mounts, knows as brake spacing.

Thank you that's all the information I needed to know.

LongBeachC10, I'd be interested once I figure out if I end up using them or not. PM me.

[BCOWANWHEELS]

just rebuild the 71 axle and put new clutch discs in posi . no big deal