Rear end issue longer than factory

[CYLFD]

Ok so I bought this truck/frame just checked to see if it was a 12 bolt didn't think to look at anything else. Well so got it home ordered my stuff from Porterbuilt. Started taking it apart and noticed the trailing arm perches had been welded on. So I took some measurements and compared it to another factory one I have and it's longer.

They are welded the same distance from the center of the reared but I'm wondering if I'll be screwed when it comes time to get wheels and tires meaning pushing the wheels out further.

My best guess is it's probably a 73-87 rear end haha

Just wondering if anybody has had this problem or ran a different rear end in their trucks. But for now I'll just be
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[JimKshortstep4x4]

You did not say how much longer the rear end is but starting in 1971 , (some 1970's) the rear ends were made 1 1/2" longer, (wider). The 71-72's rear ends will work in the older trucks and the 73 up should work also.

Jim

[special-K]

What rear end are you comparing it to? We need to know that for starters.

[CYLFD]

It seems to be about 1.5 inches longer which to my best guess it would push ea. side out .75
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[CYLFD]

I'm comparing it to a stock rear end i have from another 67. The one I have now I can tell perches were added and also it doesn't have that stud thing at the top for the factory track bar.
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[ERASER5]

All 1/2 ton 12bolt truck rear end were that wide from 70.5 to 87. The reason was to match the new disc brakes (they started a bit early as late 70s got the wider rear end). This not really a problem. The swap was usually done to gain 5 lug pattern. To be a exact drop in, the only choice was 71 and 72 rears. By using welded perches, the choices become almost infinite.

So, do you have a 5 lug pattern or not? Has your truck been upgraded to front disc brakes?

[CYLFD]

Originally Posted by ERASER5

All 1/2 ton 12bolt truck rear end were that wide from 70.5 to 87. The reason was to match the new disc brakes (they started a bit early as late 70s got the wider rear end). This not really a problem. The swap was usually done to gain 5 lug pattern. To be a exact drop in, the only choice was 71 and 72 rears. By using welded perches, the choices become almost infinite.

So, do you have a 5 lug pattern or not? Has your truck been upgraded to front disc brakes?

Yes the rear end is 5 lug the front is Porterbuilt front drop member with c4 front suspension. I can tell where the PO did some grinding on the rear end and I can tell the perches are not factory welded on.

Now the rear end I measured it against is not a 5 lug it's 6 so is that where I'm messing up are 6 lugs diff.?
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[ERASER5]

All 61 and up (before that, I have no idea) C10s had 6 lug until "71 (2X and 4X), so if you have 5 lug, there HAD to be changes. So you are correct. Modification did happen. Fast and easy way to get 5 lug rear is locate a 73 to 87 (millions of 'em) with the gear set you want. Grind off the leaf spring mounts and weld on the swing arm perchs. If you already have the gear set you want, 5 lug after market axel can be found for the early rear end, but you might spend more money that way.

As it is, your "wide" axle is the propper width to match a "normal" front disc setup. Porterbuilt fronts are narrower than "normal" to tuck the wheel a bit for a lower stance as I understand it. Correct me if I am wrong on this.

[ERASER5]

I forgot to answer the last question. Yes and no. A '61 to '70 6 lug is narrower than a '71 to '87 5 lug. Some, mine for example, is a "wide" '70 6 lug 2X rear. From mid '70 to '87 4X4 6 lug (all C10 4X4s are 6 lug) are wide. So it all come down to when it was made. My original '70 6 lug is wide, my original '71 5 lug is wide, my '69 6 lug Dana is narrow.

Since it can be difficult to figure out the year, I use a measuring tape and call it good.

[CYLFD]

Ok thank you that helps some my main concern is when I get ready to do wheels and tires I just didn't know if I'd run into a problem with back spacing etc.
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[CC69Rat]

I have a late rear end in my GMC and it's 6 lug. An easy way to tell (if it's in a truck) you can lay down underneath the truck and measure backing plate to backing plate. The early ones will be 55.5" Late being 57" Of course this matches your 1.5" findings above.

What I'm saying is not all late rear ends were 5 lug from the factory apparently (?) My truck is a late 70, so I guess that explains it. They just used whatever they had and what matched the front (discs, or 71+) I guess? Mine is 6 lug power drum up front.