Refurbishing my '73 after 48 years of ownership

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Chris, what tranny cross member did you use? Also what clutch and shifter? Your Stang is looking good!

I ordered everything for this conversion from Modern Driveline.

The clutch kit is the King Cobra 10.4, part number MD-OKC-SS26

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The crossmember is MD-6773M-CMT5

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The shift lever is the Hurst Classic MD-320-2040

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July 21, 2021

Well, today I moved to the other end of the powertrain. I removed the factory 2.75 one-wheeler-peeler and installed a new 3.81 Eaton Truetrac rear end that I purchased from Quick Performance.


First I pulled the axles.


Here's what the diff looks like after 48 years. I spent more time removing the old gasket that all the rest of the job combined! That gear lube sure is smelly...


Since the new gasket ran me $20!!, I figured it deserved a photo of it's own:


And now the finished install. Damn was it heavy. Heavier than the Tremec transmission.


Tomorrow I plan to tackle the rear brakes, install new axle seals, and put the rear end back together so I can lower the car and measure for the new driveshaft.
Your thread is coming together nicely! Your re-documenting your progress like this will make it a handy reference for the forum users.

Well, now that I have got a system down, it is not as tedious as I thought. Unfortunately I cannot just cut and paste the posts since the photos don't transfer full size. I have to re-upload them and then insert in the correct spot.
July 25, 2021

I installed new rear axle seals and brakes. Thankfully the rear bearings were good so I didn't need to replace them.



Rear drum brakes are something I really don't enjoy doing. It is a very messy job and even with the right brake tools I always end up struggling with a spring or retainer. A scrape or cut on one hand or the other just adds to the experience. I am happy to have the job behind me.

Tomorrow I dig into the heater core replacement. After researching what is involved to get to the heater core, I suspect I am going to find I prefer working on rear brakes...
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So here is a forum conversation I had regarding wiring up the Tremec to the factory harness. I have edited it down here and included it in the build thread in case others read this and have the same question. Thanks to Don C for the help.

"So having removed my FMX transmission and installed a Tremec T-5 I would like to make up a short wiring harness. I want to plug into the existing connector (previously connected to harness that ran to the automatic transmission shifter) on the engine side of the firewall.

Before I start cutting wires I am hoping for some verification that I have the correct plan:

Confirm that the Neutral Safety Switch wiring (prevents start unless in neutral) are the two Red with Light Blue stripe wires?

Confirm that the back up light wires are the Black with Violet stripe and White with Violet stripe wires?

Further that in both cases, these wires need to be closed to provide function.

Thank you!


Don C answers:

"Yes, red with light blue stripe are for the neutral safety switch, and connected together to provide power to the starter solenoid.

The back up light wires are actually called white with purple stripe and black with pink stripe, and are connected together to provide power to the lamps. The white with purple stripe wire is the one that connects to the fuse block and provides the power and the black/pink wire runs to the lamps."

Anyone interested in the full discussion will find it here:
July 26, 2021

My heater core does not leak, but at 50 years old it is only a matter of time. And while I don't need A/C in North Idaho, a heater is a must.

I removed the heater/AC box and replaced the heater core. As it turns out the job was pretty straight forward and not as difficult as I had anticipated from my research. I followed the steps in the Ford Shop Manual.

First I removed the carpet. I am installing new carpet anyway and figured I'd need every inch of room to drop the box. As you can see the floor is in good shape.


The box was in real good shape as well. No internal signs of leakage. No critter nests. No cracks or chips.

Of particular note. I did not have to remove the dash. (the Ford manuals confirm this). By removing the footwell side trim and the carpet and padding I had just enough room to pull the box right and rotate it out from under the dash. Other than removing the glove box and door no other disassembly was necessary. Here's a photo of the box prior to disassembly.


And here is is torn down. Care must be taken when removing the clips to avoid breaking them or cracking the housing.


Next I laid out a sheet of craft paper on a table. Not knowing what all parts I would be removing I labeled everything on the table as I removed things. If I am not going to be immediately reassembling something I am careful to bag and label, but if I know I am immediately putting everything back together I find the table labeling method to be more convenient.


I did buy a seal kit and replaced all the foam when I put the box back together. I also spent the extra $15 to buy a non-aluminum heater core. I have not had good luck with aluminum cores as they do not appear to hold up over time. I did check the new core for leaks (as suggested by David w Carolina Mountain Mustangs) prior to installation.

I removed and set aside the A/C evaporator. Since moving to North Idaho from Florida I find there is really no need for air conditioning and I have removed the compressor and other A/C equipment from the engine bay to give me more room and shed a little weight.

The box went back in even easier than it came out. I'd say the whole job start to finish took about four leisurely hours. Having done the job once now I could probably do it again in about half the time. All in all not the horror story I was anticipating.

Rear brakes remain my least favorite R & R. ;)
July 27, 2021

Today I took apart the front seats and cleaned them up. I also repainted and lubricated the seat tracks. They don't look too bad for 50 year old seats.


Next I took apart the instrument cluster to replace the lens and clean things up.

July 30, 2021

I did a lot of little things to the car today; filled the radiator, cleaned up the wiring behind the dash, fitted a new lens to the instrument cluster (waiting for new bulbs before re-installation), topped the transmission fluid, and made up a little wiring harness to connect the new T-5 transmission to the factory automatic transmission wiring harness:

I used Rust-Oleum Silver Ultra High Heat (1200 degrees) Paint from Home Depot on mine. They are still look perfect after 500 miles.


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If anybody has a spare set of 73 blue deluxe front seats "exactly like" yours for sale, I'd be more than a little interested! I have original knitted vinyl insert material but am hesitant on sending it to be used making reproduction covers. Afraid they will not come out like a factory set since almost all have wrinkles somewhere time and heat won't fix.

Treat them very gently getting in and out or cover when using and not at a show. The 50-year-old factory material is fragile and will at some point fail.

Here is some of that "unobtanium" center material I just found for sale if you or another owner wanted some...
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July 3, 2021

I finished the front end suspension work. All new MOOG stuff including tie rods.

I have decided to remove the air conditioning from the car. Here in North Idaho there really is no need for A/C, and there is so much more room in the engine bay without it.

Since I'm removing so much weight from the front end, and since our Mustangs tend to sit a tad nose high anyway, I cut the front springs down 1/2 coil to give me a slight drop. Now that she is down off the lift I can see how she sits with the new rear leaf springs as well.

I've included two photos, the first taken right after lowering from the lift. The second a couple of months later once she's had a chance to settle.

I'm pretty happy with the stance. Brakes next.

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Absolutely beautiful vehicle and looks so much better without the rear "Wing".-
Absolutely beautiful vehicle and looks so much better without the rear "Wing".-

Yeah, I am not really a rear wing guy either on the 71-73s. Though I really like how a '69 Mach 1 looks fully decked out with a shaker hood, front spoiler, rear wing and window louvers.

That said, I am a believer in build what you like, and drive what you want. Your car, your taste- be damned what anyone else thinks!
July 31, 2021

I bled the brakes. I used the vacuum method. All in all I fed about a quart and a half of DOT 3 into the system.


Now with brakes bled and the heater core replaced, I put the strut braces back in place, and ran new vacuum hoses. Except for the flex hose that runs from the right exhaust manifold up to the air cleaner, and the ram air vacuum lines, the engine bay is finished.


Ha! I've been looking all over for my missing deep 11/16" socket, and after posting up this photo I notice it is sitting on the washer fluid bottle. Mystery solved!
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August 1, 2021

I reassembled my instrument cluster after installing LED lights. After bench testing to confirm all was well I reinstalled the cluster. Unfortunately after screwing it back in place in the dash the lights did not light up when I turned on the headlights. Damn...

After some troubleshooting I determined that the switch was to blame. I guess after 48 years some corrosion is to be expected.


Since the dimmer resistance coil was loose on the switch and the internal contacts are suspect I decided not to try and clean it. I have ordered a new switch.

I moved on from the dash to the underside and fitted up the new exhaust system. The tailpipes are going to need a little work to get the tips to exit through the rear valence in the right spot, but otherwise all was well.


I am hoping my new driveshaft shows up next week.

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