Question on Junkyard rearends

04mustang70 · Jul 14, 2008

I have a 28 spline open rear end with 3.00 rear gears. I would really like a posi with 3.50 or so gears. Can I find one in a junk yard? What other vehicles most likely came with gearing like this?? Will any 9 inch center section with 28 spline work on my 1970 differential? Do I have to look for any specific year rearend to just bolt on to mine? Is there any good rearends in junkyards? As you can see I have no clue. Thought I would ask before I go blindly into see the junkman. Thanks in advance

calpolymustang · Jul 14, 2008

Kevinstang's Ford Nine Inch Differential Page +

Ford 9 Inch Rebuild/Gear Setup .: Articles

A few things to note:
The nodular case is hard to find, but worth $$$. If you get the WAR case, it wont be as strong (more brittle casting).

In my experience, many rear ends have different mounting arrangements, so plan on buying new perches and welding in new ones to match your leafs.

I bought a Lincoln Versailles rear for $350 then sold it for $750. people are paying a lot for em if they have ALL the emergency brake hardware. By the way, this one had 2.73 gears with a 4-pistion trac-loc. You will need a new yolk for the 3rd member if you go with a rear end that has a flat flange that mounts to the driveshaft. Most hot rodders use a yolk that bolt directly to the u-bolts, with no flat-flange.

Hope this helps...

D.Hearne · Jul 15, 2008

It'll be almost impossible to find a 28 spline 3.50 geared 9" rear in a junkyard, it was 20 years ago as well. Any 28 spline 9" chunk will work in yours. It's realitivly easy to find a 3.50 geared 9" chunk with traction loc, but it'll be a 31 spline unit. Just look under the big Bronco's. That's where I found mine. 81 Bronco. The 4wd's pickups and Broncos usually got trac-loc rears. Some 2wds too, just not as many. Cars with 9's seldom got trac-loc rears. I've had three Lincoln Versailles 9's (one actually came from under a 78 Monarch) out of these three only one had trac-loc and that was the Monarch rear.

bnickel · Jul 15, 2008

the big bronco 31 spline rear will work just fine, especially if it's a trac loc, you will have 2 options if you go this route. option one would be to change the side gears in the trac loc unit to the 28 spline units which is not difficult at all, option two would be a good excuse to upgrade to 31 spline axles.....you can get them from some places for around $150 for the pair brand spankin' new......

EDIT: sorry, the axles were actually $150 each

http://store.summitracing.com/egnse...94851288+4294908331+4294925081+115+4294908282

66blue mustang · Jul 15, 2008

i got my 8" rearend with 3.55 posi out of a mustang II.

D.Hearne · Jul 15, 2008

The Strange Axles I bought for the Comet were $400+ for the pair.

bnickel · Jul 15, 2008

D.Hearne said:
The Strange Axles I bought for the Comet were $400+ for the pair.

superior 31 splines for $150 each

Axle Shafts, Direct Fit - summitracing.com

D.Hearne · Jul 16, 2008

Yea, Superiors are a better price, but if you've got a non stock axle width.............

bnickel · Jul 16, 2008

D.Hearne said:
Yea, Superiors are a better price, but if you've got a non stock axle width.............

they also sell non stock widths as well, same price i think with an additional 15 bucks per axle to cut them to length

jlangholzj · Jul 16, 2008

how much would it be to change out the side gears on the trac loc to 28 spline?? I've been debating this very same question myself.

same setup, only in a 68 : 3.00, open, 8"

bnickel · Jul 16, 2008

if you think you can do the work yourself just the cost of the side gears and axles and of course all the stuff that goes along with it like bearings, seals, etc.

D.Hearne · Jul 16, 2008

jlangholzj said:
how much would it be to change out the side gears on the trac loc to 28 spline?? I've been debating this very same question myself.

same setup, only in a 68 : 3.00, open, 8"

An 8" rear's already got 28 spline axles. And a 9" chunk won't fit anyway. You'd have to get a whole 9" for Stang first

D.Hearne · Jul 16, 2008

bnickel said:
they also sell non stock widths as well, same price i think with an additional 15 bucks per axle to cut them to length

Wish I'd known that a year ago.

bnickel · Jul 16, 2008

jlangholzj said:
how much would it be to change out the side gears on the trac loc to 28 spline?? I've been debating this very same question myself.

same setup, only in a 68 : 3.00, open, 8"

sorry, i thought you were asking about changing the 28 spline 8" trac loc over to 31 splines. it can be done using the 9" trac loc 31 spline side gears and the correct axles. wonderful thing about the 8" and 9" is that a lot of the parts are interchangeable

jlangholzj · Jul 16, 2008

D.Hearne said:
An 8" rear's already got 28 spline axles. And a 9" chunk won't fit anyway. You'd have to get a whole 9" for Stang first

bnickel said:
sorry, i thought you were asking about changing the 28 spline 8" trac loc over to 31 splines. it can be done using the 9" trac loc 31 spline side gears and the correct axles. wonderful thing about the 8" and 9" is that a lot of the parts are interchangeable

Maybe I'm blunt, but these seem to be conflicting here.

but a 9" chunk wont fit in the 8" housing huh?

ultrastang · Jul 16, 2008

bnickel said:
sorry, i thought you were asking about changing the 28 spline 8" trac loc over to 31 splines. it can be done using the 9" trac loc 31 spline side gears and the correct axles. wonderful thing about the 8" and 9" is that a lot of the parts are interchangeable

It is true that the 28-spline axle gears from a 9-inch differential can be swapped out for 31-spline gears, but in the case of an 8-inch rear end, 31-spline axles won't work in them because the opening of the stock 8-inch differential [on the ends where the differential bearings press on] don't have a large enough bore for a 31-spline axle to fit into it.

Just to reconfirm, I took a Traction-Lok 3.00:1 8-inch 3rd member I have from a '76 Mustang II and tried to slide a 31-spline axle into the differential, but it wouldn't even get past the very outer opening going into the differential casting.

bnickel · Jul 17, 2008

ultrastang said:
It is true that the 28-spline axle gears from a 9-inch differential can be swapped out for 31-spline gears, but in the case of an 8-inch rear end, 31-spline axles won't work in them because the opening of the stock 8-inch differential [on the ends where the differential bearings press on] don't have a large enough bore for a 31-spline axle to fit into it.

Just to reconfirm, I took a Traction-Lok 3.00:1 8-inch 3rd member I have from a '76 Mustang II and tried to slide a 31-spline axle into the differential, but it wouldn't even get past the very outer opening going into the differential casting.

i've known dirt track guys here who have made up 31 spline 8" diffs around here and was told that all they did was swap the side gears from the 9" diff over the the 8" diff. i've also verified tht these same guys were running 8" diffs. now whether or not the 8" diffs actually had 31 spline axles as they said i can't say, i just took them for their word, i suppose.

also, the guys at Autoworks Intl. that built the Dynacorn Phantom car used a 31 spline 8" in that build as well.

point is that i know it can be done and it has been confirmed that it can be done, maybe it's just more involved than just swapping the side gears as i've been told previously though.

ultrastang · Jul 17, 2008

I've heard of some 31-spline axle being installed into an 8-inch rear, but I suspect it its not a stock, Ford-produced, differential(?)., or the differential's I.D. [where the axle slides in to engage the axle gears] has been bored out oversized in order to get the axles to go in(?).

In the case of the 8-inch 3rd member & 31-spline axle I have, the axle would not go into the differential at all, so that makes me wonder if the differential they are using is an aftermarket item, or if it's a stock modified unit?

On the 9-inch differentials, the bore is large enough to handle either 28- or 31-spline axles without the need for mods to the differential, other than swapping the axle gears out themselves.

Question on Junkyard rearends

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