Rear end swap questions...WWYD?

[budman k20]

I'm building a 67 c10 (with 49K miles) that has a 6 lug posi rear. I also have a complete 72 chassis to swap out mileage unknown. I have read up and searched converting 6 to 5 lug rear ends. Both rears have 3:73 gears, and I want the posi either way. So I have to either put the posi unit into the wider 72 rear or put aftermarket 5 hole axles in the shorter 67 rear. I think it would be less work to put axles in the 67 rear.
So my questions are:
Would you use the 67 rear and why?
Would you use the 72 rear and why?
Are there fewer wheel backspacing options for the 67 over the 72?
Can I just bolt in the posi carrier in the non posi rear and not have to reset the ring and pinion gears? I'm guessing I would have to re-shim for backlash but not have to change pinion depth...

I plan on using the complete 72 disk 5 bolt front end.

Thanks in advance for helping me decide what to do!

[sprint_9]

I would use the 67 simply because I like the wider dish it allows you to have with the rear wheels. If cost is an issue the 72 would be cheaper since you wouldnt need to buy aftermarket axles.

Either way I would have it gone through/rebuilt, cleaned up, new bearings, seals, check things over good.

[SS Tim]

The 71-72 (and late 70) rear is a little wider, want to say 1.5" to better match the wider front disc brake track.

If you swap the posi case you need to do a complete ring and gear reset. I for one don't even like transfering used gears but you never split a set.

Might want to consider the rear brake condition too unless you are planning new from the backing plate out either way.

[budman k20]

If you swap the posi case you need to do a complete ring and gear reset. I for one don't even like transfering used gears but you never split a set.

Yea I would keep the gear sets together and your comment about the disc rear made me wonder if aftermarket disc brake kits would be the same for either year rear? If there is no clear advantage to the 67 other than lower mileage I'm leaning towards putting the 72 rear on it.

[dennislbrooks]

I thot the 67 axles were shorter than the 72 axles, hence axle and those housings are not interchangeable --may be wrong. So if you want 5 lug to match the 72 front disc --use the 72 axle --switch the posi.

I think the 72 axles will extend too far from the 67 housing/tubes.

[budman k20]

So I have to either put the posi unit into the wider 72 rear or put aftermarket 5 hole axles in the shorter 67 rear

Like I mentioned in my post the 67 axle is shorter. I have the equipment to re-drill to 5 lug and turn the 67 axles or I could buy aftermarket. I'm asking people to provide any known advantages to one or the other.

[dennislbrooks]

oops -- I have redrilled also -- you have to drill or mill thru one partially welded hole as you know but can be overcome.

[SS Tim]

A wider axle (wms to wms) will allow a wider zero offset set wheel given the same suspension. In my book zero offset (or near to) is important on a semi-floating axle.

[jdalexa84]

Amazon.com: Motive Gear MG6569 8.875" Axle...These are what I used. Fit great and not much more than a set up kit. Plus you have to buy tools to change it over and come out at about the same price and have to do more work. Might spend an hour if you really take your time with the new axles. If you go with the 72 rear end you are using 44 year old axles so who knows what they have been through

[budman k20]

dennislbrooks... no worries!

jdalexa84... Great price on new axles in a low mileage rear... have to think about that option.

SS Tim...the constant battle between form and function! I won't be hauling anything in this truck...but I do like to drive at a brisk pace so good handling is not lost on me either.

[68bowtie]

what wheels/tires are you planning on running?

[budman k20]

what wheels/tires are you planning on running?

Not sure yet. It is green and looks like this one. Same color and trim

I do like the salt flats or 338's depending on the costs?

[68bowtie]

Originally Posted by budman k20

Not sure yet. It is green and looks like this one. Same color and trim

I do like the salt flats or 338's depending on the costs?

that's one of my favorite trucks. you better be posting some pictures soon so we can all drool!

to answer the question though, if it was me i would figure out the exact wheel/tire combo and figure out what axle width would work best. if it would help avoid a custom wheel backspace or rear end mods that seems like the best route to me. i like summit racing for the interface and ability to filter wheel specs to pin down options.

[dennislbrooks]

If needed - I have a pair of 5 on 5 - 1" wheel spacers with nuts that I will not use as my trucks are 6 or 8 or 4 3/4 x5 on the 42. I hope I am not scolded on the deadly sins of wheels spacers.

[budman k20]

that's one of my favorite trucks. you better be posting some pictures soon so we can all drool!

Well you wont drool over mine! It is a LWB right now but I have a 68 SWB frame and a 67 short bed and complete 72 chassis that I'm swapping out parts to make it the way I want it. Some people may call it a Frankenstein truck but I'm building it to my taste and putting the best metal on it I can find.

[mike16]

all things being equal your best bet is to stick with what you have. a low mliage truck favors the origonal drive train too and the cost of simply switching everything over is not too cost effective. cheaper simply to buy the wheels you like in a six lug configureation.