Off the shelf 3rd member that drops into our cars?

[giantpune]

I have a '73 that came with the 2.75 open diff. It looks like its about due for rebuild or replacement. I would like to go to something around a 3.25:1 limited slip.
When shopping around for a complete 3rd member, there are variables like axle spline count and which bearing caps the yoke is for. I know some 3rd member housings and caps are bigger than others and may not just plop right in.

Do you guys have any suggestions for a 3rd member that is known to just bolt right into the 73 mustang and work without any surprises?

 

[Bentworker]

You could purchase any new third member that has the same spline count as your axles - with one catch.

Make sure whatever one your purchase has a crush sleeve eliminator kit in it. (The pinion preload is set by shims between the two pinion bearings instead of a crush sleeve).

You order up a crate 3rd member with a 1350 series yoke.

When it arrives you remove the old yoke from your car, clean it up and install it on the new third member. The 1350 series yoke goes on a shelf and waits for the day it is needed because of added horsepower.

This only works if your rear end is set up with a crush sleeve eliminator. If it does not have that and you swap yokes most likely failure will occur and any warrantee you had will be out the window.

 

[Tnfastbk]

https://www.speedwaymotors.com/Ford-9-Inch-Gear-Posi-3rd-Member-Assembly-OEM-Case,478733.html
you can call these guys and they will walk you through what will work as will summit racing

https://www.summitracing.com/search...e-assembly?SortBy=Default&SortOrder=Ascending

 

[giantpune]

You could purchase any new third member that has the same spline count as your axles - with one catch.

Make sure whatever one your purchase has a crush sleeve eliminator kit in it. (The pinion preload is set by shims between the two pinion bearings instead of a crush sleeve).

You order up a crate 3rd member with a 1350 series yoke.

When it arrives you remove the old yoke from your car, clean it up and install it on the new third member. The 1350 series yoke goes on a shelf and waits for the day it is needed because of added horsepower.

This only works if your rear end is set up with a crush sleeve eliminator. If it does not have that and you swap yokes most likely failure will occur and any warrantee you had will be out the window.

I think my existing yoke is the issue. Mine is leaking out the front pretty moderately. And I think the bearings are also toast.

And which yoke do we need? You said 1350. @Tnfastbk linked one that says 1310 series.

 

[Sheriff41]

I've used Quick Performance <quickperformance.com> when buying a new differential. The 1310 yoke is original and fine for daily driver and weekend cruisers. 1350 is a HD upgrade you would want to use with an upgraded drive shaft for more performance oriented driving.

 

[Hemikiller]

WES-T is an open diff 2-pinion 28 spline 9". The yoke on yours is a "tall" 1310 series yoke, used in pretty much all 71-73 351 powered Mustangs except for the highest performance cars.

Alan Van Aunen owns and runs 8and9inchfordrears. The guy knows his stuff, and will be getting my next diff order. He builds the rears personally, not some guy who works for a company.

https://8and9inchfordrears.com/
He also has an eBay store so you can see what the pricing and options are. He quoted me prices below that on the eBay listings a couple months ago.

https://www.ebay.com/usr/av1141

 

[giantpune]

WES-T is an open diff 2-pinion 28 spline 9". The yoke on yours is a "tall" 1310 series yoke

That was gonna be my next question. I saw there are 1310 short and 1310 tall yokes.

 

[Bentworker]

I think my existing yoke is the issue. Mine is leaking out the front pretty moderately. And I think the bearings are also toast.

And which yoke do we need? You said 1350. @Tnfastbk linked one that says 1310 series.

I thew out 1350 as it is the performance standard. Good for plenty of horsepower. Only suggested because it is common, Will NOT bolt right in.

I really doubt your yoke is trash. It might have some wear on the sealing surface, which could be repaired with a Redi Sleeve. You do have to put a small amount of sealant on the pinion splines so that oil does not weep out of the nut area.

My suggestion was geared at opening up the options for you. You could get any 28 spline third member from Jegs, Summit, speedway or whatever other retailer floats your boat- and then swap yokes. Again, this is only a valid option if the third member was set up with a crush sleeve eliminator.

Personally I’d just pull it and rebuild it. If you have good eyesight, dexterity and some strength a 9” is one of the least speciality tool intensive rear ends to rebuild. It isn’t easy, but it isn’t hard. A moderate investment in nice tools (dial indicator & inch pound dial or beam torque wrench) is all you need outside of “normal” tools- as long as you or a buddy have a hydraulic press.

All this rambling aside other folks have named some good options for you if you truly want an out of the box bolt-in third member.

 

[giantpune]

I really doubt your yoke is trash. It might have some wear on the sealing surface, which could be repaired with a Redi Sleeve. You do have to put a small amount of sealant on the pinion splines so that oil does not weep out of the nut area.

The car starts to shake once it gets to 40MPH, even when I throw it into neutral and coast. The yoke looks to be in the roughest shape so it is getting added to the list of things that are getting repaired or replaced. When I take this apart, I will be doing universal joints, 3rd member, and axle bearings and seals all in one go.

Personally I’d just pull it and rebuild it. If you have good eyesight, dexterity and some strength a 9” is one of the least speciality tool intensive rear ends to rebuild. It isn’t easy, but it isn’t hard. A moderate investment in nice tools (dial indicator & inch pound dial or beam torque wrench) is all you need outside of “normal” tools- as long as you or a buddy have a hydraulic press.

I do have a press and all sorts of indicators and whatnot. I would probably be more inclined to rebuild one if I could watch over somebody's shoulder for my first one. The plan was to buy a complete 3rd member off the shelf to have something I know works. Then I have a spare one I can attempt to rebuild on my own and if it craps the bed, I still have the good one.

 

[tpj71mach]

This is a question that I have been contemplating recently, hoping to order a bolt in third member. I think my yoke is a 1310 tall and I assume because it is a nothing special 3.0:1 open case differential with non-staggered shocks that it would be 28 spline axles, is this correct? I attached pictures of my differential and the ID tag if that helps determine what it has. Thanks

 

[Sheriff41]

This is a question that I have been contemplating recently, hoping to order a bolt in third member. I think my yoke is a 1310 tall and I assume because it is a nothing special 3.0:1 open case differential with non-staggered shocks that it would be 28 spline axles, is this correct? I attached pictures of my differential and the ID tag if that helps determine what it has. Thanks

Yep, that's the tall 1310 yoke. 99.9-percent chance of 28-splined axles. 3.00:1 makes for a nice, lazy cruiser.

Your detailing looks really good, as usual.

 

[bill1101]

Don't know what your budget is, but I have had really good luck with Strange Engerineering. You can buy a complete bolt on rear end for under 3K. They will narrow it for no extra cost. You can customize it with anything you want, again budget willing. It didn't cost as much as I thought and they will walk you through the whole process. I ended up narrowing my rear end a half inch on each side. They can also set you up with just the center section

 

[Spike Morelli]

My advise is not to try and figure out any of this , unless you are in the business. I bought a 9" center section with Trac-Loc, 31 spline gears, and some gearing I don't really remember,from some guy on the East Coast, had it shipped sight unseen to Los Angeles, and took it to a shop in my area that SPECIALIZED in rear ends. The 9" Ford is widely used, and there are lots of parts available for them. The shop I used completely overhauled my newly purchased, but very used, center section, swapping out the 31 spline components for 28 spline to match my rear axle, put in the gearing ratio of my choice, new bearings , clutch pack, yoke, etc. The shop carried everything necessary. All I had to do was install the diff, and get my speedo recalibrated to reflect my new gearing. The cost was fairly reasonable as I remember. Let a professional do up your needs. You're not going to learn Portuguese overnight either.

 

[Sheriff41]

My advise is not to try and figure out any of this , unless you are in the business. I bought a 9" center section with Trac-Loc, 31 spline gears, and some gearing I don't really remember,from some guy on the East Coast, had it shipped sight unseen to Los Angeles, and took it to a shop in my area that SPECIALIZED in rear ends. The 9" Ford is widely used, and there are lots of parts available for them. The shop I used completely overhauled my newly purchased, but very used, center section, swapping out the 31 spline components for 28 spline to match my rear axle, put in the gearing ratio of my choice, new bearings , clutch pack, yoke, etc. The shop carried everything necessary. All I had to do was install the diff, and get my speedo recalibrated to reflect my new gearing. The cost was fairly reasonable as I remember. Let a professional do up your needs. You're not going to learn Portuguese overnight either.

o que ele disse (Portuguese for "what he said")

 

[Bill73Ragtop]

https://8and9inchfordrears.com/
I replaced my 3rd member on my 69 vert with new Trac Lok 3:55 last year. Pricing was reasonable and Alan was very good to work with.

 

[jakosaur]

I actually just did a rebuild of my third member over the weekend. It went fairly smoothly with only one new specialty tool (I am a quality engineer so I already had all of the precision measuring tools handy. Those probably cost a lot). All I needed was a $30 bearing puller from Harbor freight, and a full day of work. Now I have the 3.50 ratio installed for the AOD swap I’m doing. If you’re slow and methodical in your work, it really is easy but time-consuming, but will also save thousands of $ over buying a drop-in. I think it cost me about $300 including tools. You could also source your own parts and send it to a shop for much less than buying a drop-in. Just my $0.02.

 

[cv_72mustang]

Mine sounded and felt like the space shuttle! Along with the leaks.

I had mine rebuilt and went from 2.75 to 3.0 If I remember I could not get a 2.75 Perfect for my ice cream car. The speedometer is a little off but a little quicker at the start.

 

[giantpune]

Thats 2 referrals for Alan. The hive has spoken. I called him up and hopefully when he gets back from vacation will be able to put something together for me.

 

[kulfurs]

I did a QP swap about 3 months ago. Works great bolted right in. 3.50 gears posi. Using a AOD trans

 

[Spike Morelli]

On my car, as it came with A/C, and an FMX, the 3.5:1 ratio was never available for that particular combination, and so, a simple nylon drive gear swap at the trans wasn't in the cards for me. My local Speedo Shop had a unit that goes inline on the speedo cable, called a "ratio box", a compact little piece that they can load numerous combinations of gearing to make the stock speedo accurate. Just mentioning it as an option, for some may not be aware that exists. As for the advising to let a rear end shop do the work, they have the parts, and the experience. Obviously, there are those on the boards who are capable of doing the job, but they aren't ,by and large, the ones posting for advise. I assume anyone inquiring here has little to no experience in differential overhauling, ( include me in that group ), there's other things I'm good at, at I'm OK with that.