Ford explorer 8.8 rear end swap into a 71

I am seriously considering doing this swap soon and wanted to compile all the information out there into one thread. If i pull the trigger on this I will make this into a "how-to" thread as I do the swap. I found a 96 explorer in the junkyard with the 3.73 limited slip and only 100K on the odometer so seriously tempted to go get it for $250. Just need a pick up truck and a friend

This is the best thread out there that I can find about the swap:
https://www.vintage-mustang.com/threads/8-8-rear-end-in-71-mustang.1188868/

Good info here:
https://www.therangerstation.com/tech_library/Explorer8_8.shtml

and here:
https://www.therangerstation.com/tech/ford-8-8-inch-rear-axle-history-and-specs/#gsc.tab=0

The current thought is to use an adapter on one side to get the correct length as opposed to pulling the axle tube and swapping axles.

For anyone who has done this, I will take any tips, tricks, or advice from your swap!

EDIT: I pulled the trigger on the swap so I am going to use the OP as a spot to keep a parts/price list, measurements, and to-do list so it is easily found. My Mach is factory power brakes so I need to upgrade the master cylinder and add a proportioning valve whereas those with manual brakes may not have to do this.

Parts/Prices:
Junkyard 8.8: $300 with brakes (would have been $250 without brakes)
Leeds Master cylinder and Proportioning Valve: $360
1.5" Wheel adapter: $45
Spicer 1330 U joint: $23
All new brake parts (except calipers) from Rockauto: $172 shipped
Spring perches: $38 shipped
E-brake adapter: $33 Shipped
Fluid: $50 (ballpark)
Total: $1,071

To Do List:
As mentioned above, I have factory power brakes which makes the job slightly more involved and expensive if wanting to be done "correctly"; this will require upgrading the MC, booster, and adding a proportioning valve.

If you read through the older mustang forums, a lot of owners will actually pull out the driver side tube of the axle assembly and have it shortened to have it fit early mustangs. As our cars are actually wider, the same concept could be applied to our cars and have the passenger elongated. That would require buying 2 complete rear ends assemblies and having a shop do a lot of work for you. I have decided to go the budget route and just use an adapter on the passenger side to get it "good enough". I will post measurements below.

-Clean axle and cut off all stock perches and mounts
-Weld new perches to achieve ~3.5* pinion angle
-Weld axle tubes to prevent twisting
-Fabricate/modify spring plates for shock mount
-1.5" wheel adapter on passenger side
-Install 8.8
-Verify correct driveshaft length
-Replace brake components
-Install new master cylinder, booster, and proportioning valve
-Bleed brakes and enjoy!

Measurements:
71-73 axle width: 61.25"
71-73 spring perch width: 43" (center to center)
91-01 and 01-03 explorer/sport trac axle width: 59.625
-with 1.5" adapter = 61.125"
New spring perches should be welded 21.5" out from center of axle assembly or 9 1/16" in from WMS
Pinion angle should be ~3.5*

I'd take a look at the rear end from an Explorer Sport-Trac. I don't recall if it's all years, but I thin the width is very close to the rear end that came in our cars. That's what I did and I know a couple other people here (@tony-muscle I think?) have done that swap as well. The only issue there is it's offset so there can be clearance issues at the rear of the tunnel that need to be addressed.

Edited to add a couple tidbits.

Here's the spring perches I used: https://barnes4wd.com/products/anti-wrap-leaf-spring-perch-pair-dana-60-ford-8-8-ford-9

And here's an adapter to convert the parking brakes on the 8.8 to work with the existing cabling. These worked great for me. https://www.theflopshopoffroad.com/products/ford-8-8-swap-e-brake-cable-adapters

I did this swap from Sportrac Explorer probably 15+ years ago. No need to swap axles. The width is very close and the pinion offset isn’t too bad. Slight clearancing is required on the tunnel in rear with a small hammer and block of wood. I used the rear piece of the explorer driveshaft on the mustang shaft. I made my own arms for the e brake setup to use stock mustang cables. You will need to cut off spring perch mounts and weld new ones on in correct angle and location. I made the spring u bolt plates to match the stock mustang ones to mount tge shocks to. It’s some work but well worth if you have some fab skills. 3.73 gears, posi, and disc brakes in one shot for couple hundred bucks isn’t bad.

https://www.therangerstation.com/tech/ford-8-8-inch-rear-axle-history-and-specs/#gsc.tab=0

From what I can tell, the 95-2000 and 2001-2003 sport trac all have the same rear end in them which are all 59.625 inches wide. The 71-73 axles are 61.25 inches wide. My thought would be to offset the axle to center the diff better and use an adapter on the short side.

Thanks for the links above! I am hoping to snag an axle this week if I can find time and a helper.

Hey @TheDude can you double check your link for spring perches

I bought mine from summit racing.

351mach1 said:

Hey @TheDude can you double check your link for spring perches

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It's corrected in the post and here https://barnes4wd.com/products/anti-wrap-leaf-spring-perch-pair-dana-60-ford-8-8-ford-9

TheDude said:

I'd take a look at the rear end from an Explorer Sport-Trac. I don't recall if it's all years, but I thin the width is very close to the rear end that came in our cars. That's what I did and I know a couple other people here (@tony-muscle I think?) have done that swap as well. The only issue there is it's offset so there can be clearance issues at the rear of the tunnel that need to be addressed.

Edited to add a couple tidbits.

Here's the spring perches I used: https://barnes4wd.com/products/anti-wrap-leaf-spring-perch-pair-dana-60-ford-8-8-ford-9

And here's an adapter to convert the parking brakes on the 8.8 to work with the existing cabling. These worked great for me. https://www.theflopshopoffroad.com/products/ford-8-8-swap-e-brake-cable-adapters

Click to expand...

Not me. I am still faithful to my 9"

100k on the odometer

Damn. Only 100k? that's crazy. my 2007 exploder just turned 223k and still runs and drives like new.

351mach1 said:

https://www.therangerstation.com/tech/ford-8-8-inch-rear-axle-history-and-specs/#gsc.tab=0

From what I can tell, the 95-2000 and 2001-2003 sport trac all have the same rear end in them which are all 59.625 inches wide. The 71-73 axles are 61.25 inches wide. My thought would be to offset the axle to center the diff better and use an adapter on the short side.

Thanks for the links above! I am hoping to snag an axle this week if I can find time and a helper.

Click to expand...

I can't find the numbers easily, but the sport trac was wider and within something like 1/2-3/4" of our cars. Obviously don't take my word for it and verify but I see it listed incorrectly all over the place.

Well, the deed is done. They got me for $300 out the door because they wanted me to pay for the brakes

There were no sport tracs at the yard and this unit only has 100K on it so with a 45$, 1.5" adapter, I'm gonna call it good enough for Frankenstein.

Edit: Everything online says the explorer and sport trac rear ends are identical but I would love to see a real world measurement.

I am now putting together a list of parts needed, prices, measurements, and the to do list. Will follow up when I have it all figured out.

And for any naysayers out there: I wish I could have just found a 9", threw it in, and called it a day but I have been looking for over 2 months and nothing has popped up around Las Vegas. The mustang market here is slim pickings. Plus I figure I would still have to pay 5-600 for the rear end, 1000 for the gears and trac lok, and another 150-200 for seals, brakes, and fluid. So I am looking at $1700-ish for a 9" would be my estimate.

I will be curious to see what this comes out to be but I am hoping sub $800 and that will give me disc brakes, the gears I want, limited slip, 31 spline axles. Plus it's fun to fab up this stuff. So here we go!

351mach1 said:

I will be curious to see what this comes out to be but I am hoping sub $800 and that will give me disc brakes, the gears I want, limited slip, 31 spline axles. Plus it's fun to fab up this stuff. So here we go!

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Dont forget to add the price of a new master cylinder, proportioning valve, and the hard lines to connect all the parts. The stock disc/drum components are not meant for 4 wheel discs. It will stop, but it won't feel right. Ask me how I know.

Nobody makes a direct swap in disc/disc master cylinder and proportioning valve for our cars. Leed makes some that will bolt up to the firewall and pedal for like $320. They put the proportioning valve in a non-stock location. So there's a new set of lines you need. I see they do sell a kit of lines. No clue if its meant for their master cylinder setup or what.

Hmm I was wondering if that was gonna be the case or not....more research and money! @giantpune Have you done the swap?

Wildwood appears to potentially have some solutions...

https://www.wilwood.com/MasterCylinders/MasterCylinderValves

Leed says this is a 4 wheel disc setup with proportioning valve:
https://leedbrakes.com/i-21155648-h...h-adjustable-valve-for-1971-1973-mustang.html

mrgmhale said:

Make certain your current drum brake Residual Pressure Check Valve is removed when you switch to drum brakes. See the attached file.

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This was borrowed from: https://7173mustangs.com/threads/disc-brake-conversion-options.42598/

Summit explains disc/drum/power/manual master cylinders


Sounds like @turtle5353 may have written all this up before that poofed at some point.

I am hoping that by the time I am finished this thread it will be the comprehensive guide to doing this swap in our cars.

I ran the stock proportioning valve and stock drum/drum master. Been running that for years. Non power but works great. I did swap the front drums with 72 convertible disc. Still running stock drum master.
Some day I will swap over to the power disc booster, MC, and pedal. I have those parts just haven’t done the swap yet.

351mach1 said:

Hmm I was wondering if that was gonna be the case or not....more research and money! @giantpune Have you done the swap?

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I have not done the swap on our 71-73 mustangs, so I can't say exactly which parts would be a direct swap in. I do have a 69 mustang and a 73 nova that previous owners swapped the rear to disc brakes without changing anything else. They're both pretty disappointing in the brake department. On the nova, I did swap the master cylinder and distribution block to the leed kit. It made a world of difference.

turtle5353 said:

I ran the stock proportioning valve and stock drum/drum master. Been running that for years. Non power but works great. I did swap the front drums with 72 convertible disc. Still running stock drum master.
Some day I will swap over to the power disc booster, MC, and pedal. I have those parts just haven’t done the swap yet.

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100% correct with the master cylinder. I'm running a four wheel 12 inch disc kit purchased from Baer Brakes. My 72 Q-code was factory 4 wheel drum. When I spoke to Baer about what master cylinder to use they stated the factory 4 wheel drum unit and distribution block is perfect for the 4 wheel disc conversion. I have installed an in cabin rear perportioning valve for on the fly front/rear bias fine tuning.
Brakes stop on a dime with nine cents change.

Cleveland Crush said:

100% correct with the master cylinder. I'm running a four wheel 12 inch disc kit purchased from Baer Brakes. My 72 Q-code was factory 4 wheel drum. When I spoke to Baer about what master cylinder to use they stated the factory 4 wheel drum unit and distribution block is perfect for the 4 wheel disc conversion. I have installed an in cabin rear perportioning valve for on the fly front/rear bias fine tuning.
Brakes stop on a dime with nine cents change.

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Which distribution block? I ask, because I'm going through my car now about to sort out the brakes. It is currently a mix-match of parts. The distribution block and a couple of the steel lines came out of my parts car, which was a 72 with 4 wheel drums. If it is useful for something other than a paper weight, I won't toss it out.

giantpune said:

Which distribution block? I ask, because I'm going through my car now about to sort out the brakes. It is currently a mix-match of parts. The distribution block and a couple of the steel lines came out of my parts car, which was a 72 with 4 wheel drums. If it is useful for something other than a paper weight, I won't toss it out.

View attachment 97948

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Here ya go pune:
Factory installed 4 wheel manual drum block from April, 1972. Now used with 12" manual four wheel disc.