1979 Ford F100
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This truck originally belonged to a close friend of mine, John Sheppard, and over the years I'd helped him do a bunch of regular work on it along with a few upgrades. It's a good work truck with a 302 V8, a 4-speed overdrive "SROD" transmission, and a 9" rear axle. Befitting a good work truck, it has about zero options other than two-tone green and black paint, and a replacement "long block" engine from Schuck's Automotive in the recent history before John bought the truck. John's son Trey was slated to become the eventual recipient of this truck, so we made an effort to keep it going so he'll have something to learn about cars on and take pride in working on when he gets old enough. It was getting a bit run-down and rusty, and that transfer was in question, and then it developed a rod knock. (So much for that high quality rebuilt engine...) I took possession of the truck to fix it, and eventually gave John a 1989 Ford F150 in exchange for me keeping this truck to mess around with.


Related Pages

As individual part of this page get too long, I move them off to separate pages to keep things more manageable. Here's the current list of separate pages.


Basic Stuff/History

I used to live in the same town as the previous owner of this truck (John), and we helped each other do all sorts of preventative maintenance on each other's vehicles, as well as diagnose and fix the usual list of problems that crop up on older cars.

Most amusing was that his heater never worked for years, and everyone hated riding in John's truck in the winter because it was so darned cold. John never cared to investigate and fix it because he's basically cold blooded. I was sick of freezing my butt off every time I was in his truck, and the first time I was under his dash, I noticed that the heater door control cable had fallen off the arm that protrudes out of the heater box. 30 seconds later, he had a heater again. He rarely used it, but it did work when the passenger demanded some heat.

At one point we added some basic gauges under the dash, as well as a tach on the column so he could keep tabs on things. They're still there and working, and I'm going to continue to enjoy/use them after the EFI conversion.



The replacement motor from Schuck's (installed just before John bought the truck many years ago) decided to go south shortly before I got the truck. It developed a minor rod knock and the oil pump appears to have basically quit making oil pressure - so it was time for a replacement. At about the same time that the motor developed problems, I happened into a 1985 Mustang with a 5.0L engine, and the original plan was to use that engine to replace the existing and very tired engine in the truck. It needed a basic rebuild, but seemed like it would be a reasonably good rebuild candidate. I also had a decent 1987 Mustang engine laying around, plus a couple of basically complete 1987-1993 5.0L EFI setups laying around. All I really needed to try and swap the truck to EFI along with the new motor was a suitable gas tank out of a later model F-series truck with an EFI in-tank fuel pump. Frankly, it's less hassle for me that rebuilding and tuning the carb would be - wiring and computers make more sense to me than carbs do, at least for tuning purposes. Yes, I am a geek. After I made the decision to go with an EFI setup and started picking up a few odds and ends I still needed, I decided to go with the 1987 Mustang engine for this project.



The original transmission is a "SROD" (single rail overdrive) 4 speed manual transmission, with 4th gear being an overdrive gear. Here are three pics of the trans tag that we took a long time ago. Why three pics? Because we are apparently a couple of goobers who can't manage to get a single good picture that is both in focus and not over-exposed with the flash. Between all three you can make out pretty much all of the info on the tag.

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The codes on the tag are something like this:


D8TRMA  1668

The "RUG CD" identifies this as the SROD transmission. It's similar in appearance to the Toploader transmissions, but it's not the same. Unlike the Toploader, this variation has a reputation for being weak in performance applications and is not considered to be a "desirable" transmission for performance use. The "AK17" is the year and date code for when this transmission was built - A is 1979, K is October, and 17 is the day of the month. "D8TRMA" is the "transmission assembly number prefix and suffix" - at least that's what the factory service manual calls it. "1668" is the serial number of the transmission. I'm still trying to sort out the ratios it really has - I really need to do this to sort out any possible transmission swap options for the future. The factory manual only lists "RUG BP" in the transmission tag decoding, and I think that two-letter suffix indicates the ratios. For that one the ratios are listed below.

Trans First Second Third Fourth Reverse
RUG BP 3.29:1 1.84:1 1.0:1 0.8:1 3.29:1
RUG CD ???:1 ???:1 1.0:1 ???:1 ???:1

The plan for now is to leave the existing trans in place with the new motor and use it as-is. I won't be driving the truck very hard or do any drag-race style launches, so the transmission will (hopefully) continue to lead a long and happy life behind the new late-model motor. The only hitch will be that I needed to swap the flywheel to a later model unit to match the "50oz imbalance" of the later model engine. I originally thought this would be no big deal - used Mustang 5.0L flywheels with plenty of service life left in them are readily available around here - but as it turns out, the flywheel in the trucks in larger than the flywheel used in the Mustangs. The F-series manual transmission requires a 164 tooth flywheel with an 11" clutch, while the Mustang manual transmission requires a 157 tooth flywheel with a 10.5" clutch. I learned enough researching this and figuring out what flywheel to buy that I started a tech page about Ford flywheels and flexplates.


Rear Axle

The original rear axle (currently in storage in my shed) has these codes:


275 9  356A

  • The "WDM CJ" decodes to a 2.75:1 ratio, non-locking, 28 spline rear axle with a 9" ring gear from a 1979 F100 or F150, or a 2.75 ratio non-locking 31-spline rear axle with a 9" rear gear from a 1980-82 Ford F100 or F150.
  • The "9AD" is a extra number for interchange purposes. Most books ignore it from what I can see. I would guess that it's extra details about the entire original axle usage so Ford could track what specific model/application it was used in?
  • The "275" indicates the ratio and that it's not locking. A locking unit would be tagged as "2L75". No love here.
  • The "9" indicates the diameter of the ring gear in inche and that it's a 9" ring gear.
  • The "356A" is a build date and/or build plant code that I have not been able to decipher yet.

No surprises here - since it was the original axle, the codes line up with this truck.


The replacement rear axle (currently in the truck) has these codes:


370 87 3024

  • The "WDM V" decodes to a 4.11:1 ratio, non-locking, 28 spline rear axle with a 9" or a 8 3/4" ring gear from a 1963-1972 F100. The 4.11:1 ratio decoding here does not agree with the rest of the tag which specifies a 3.70:1 ratio. The 9" of 8 3/4" ring gear decoding disagrees between different web sites, but the rest of the tag indicates it's likely an 8 3/4" ring gear.
  • The "OGC" is a extra number for interchange purposes. Most books ignore it from what I can see. I would guess that it's extra details about the entire original axle usage so Ford could track what specific model/application it was used in?
  • The "370" indicates the ratio and that it's not locking. A locking unit would be tagged as "3L70". No love here. This disagrees with the decoding of the rest of the tag on all of the websites I found, which specify this was a 4.11:1 ratio rear axle. I tend to believe the tag is correct at this is a 3.70:1 ratio axle.
  • The "87" indicates the diameter of the ring gear in inches, and that it's a 8 3/4" ring gear. This disagrees with the decoding of the rest of the tag on some websites I found, but I'd tend to believe the tag is internally consistent and this is a .
  • The "3024" is a build date and/or build plant code that I have not been able to decipher yet.

So, we stepped up in ratio a good bit but stepped down from a 9" to a 8 3/4" rear diff. For what this truck gets used for, that's fine. If I found a better carrier super cheap or this one blew up, I'd consider swapping it.


Air Conditioning

This section got long enough to make into it's own separate page. I added AC from a series of Craigslist purchases and a 1977 Ford F250 parts truck.



This section got long enough to make into it's own separate page. I'm running Summit headers with an X-pipe and basic mufflers.


Cooling System

This section got long enough to make into it's own separate page. It's a conglomeration of various factory bits and a bit of creative thinking.


Previous Upgrades

These were all done before I owned the truck.

4 bbl intake and carb. Our first major customization project was swapping the original 2bbl carb and cast iron intake manifold to a 4bbl carb on an Edelbrock aluminum intake manifold. I had some extra cash, and I found a great deal on the parts on eBay, and bought them as a surprise birthday gift for John - he's helped me on a number of projects and it seemed like a nice thing to do. The picture below was what I sent to him to let him know what I had waiting for him the next time he brought the truck over to my house so we could work on it.

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Better rear axle gear ratio. The other major project was swapping the original 9" rear center section for one with a higher gear ratio. The original rear gearing was a 2.75 and was very incompatible with the gearing in the original transmission. The truck was hard to to start off from a stop in first gear (burned clutches from slipping the clutch and/or impromptu unintentional burnouts from disengaging the clutch too fast), and it actually had so low of an RPM in 4th gear (overdrive) that the gas mileage was horrible. We stepped up to a 3.70 rear and drivability, mileage and overall performance all jumped up noticeably. Yes, it really is possible to have a rear axle ratio that is "too low" and causes a serious drop-off in gas mileage. Comparing the vacuum gauge at cruise in top gear before and after the rear axle ratio change was enlightening. Before the vacuum was very low and you had to give the engine a lot of gas to keep your speed. After, the vacuum was noticeably higher and you didn't need to give the engine as much gas to keep your speed. It's all about running in a more efficient RPM range so the engine could make the best use of the fuel you gave it.

Closed cooling system conversion by adding a coolant overflow tank. We converted the truck to a closed cool system by adding a coolant overflow tank from a '80s Ford vehicle. Simple, easy, and keeps all of the coolant in the engine even after ongoing hot/cold cycles. When the engine heats up, the coolant expands out of the radiator and into the overflow tank via the small rubber hose attached at the radiator filler neck. When the engine cools back off again, the coolant is sucked back into the radiator for the overflow tank, thus ensuring that the radiator is full at all times. Without this, it's considered "normal" to have the coolant not come up to the top of the radiator when cold, and if you run the engine hotter than "normal", some coolant will drop onto the ground from the small rubber hose attached to the radiator filler neck. This means it's common to have to add some coolant over time - not cool, and messy when it drips.

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This is the truck as it arrived in my driveway to prepare for the engine replacement (see below). The best part of this is that the Ford purists will be suitably aggravated that a Chevy was used to rescue a Ford. :-) I took some pics of the existing wiring work we had done already, plus the engine and body as they were when it arrived in my driveway. There are a number of small things that need fixing, and I'll handle them along with the engine work.

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Here's the 1987 Mustang engine installed into the truck. These first few pictures show it with a set of fuel rails from a 1989 F150 that I parted out. I was hoping to use the entire fuel system from the 1989 F150 because it would have simplified the plumbing of the high pressure fuel line, but no such luck was to be had. The upper intake from the 1987 Mustang engine hit the pressure regulator on the fuel rails from the 1989 F150 and not even a 1" spacer between the upper and lower intakes looked like it would have cured it, so I was back to using the Mustang fuel rails and trying to combine them with the F150 EFI fuel system I would be installing along the driver's side frame rail.

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As a result of that problem, I installed a set of fuel rails from another Mustang EFI system I had laying around, and then everything cleared just fine. Unfortunately, this means I need to do something different than I had planned for the EFI fuel pumps and lines to mate up the output of the high pressure pump from the 1989 F150 to the fuel rails from the Mustang.

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Here's a picture of the serpentine belt system for reference.

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This is a picture of a friend of mine who was helping out that day - Trey "Wilson" Sheppard. Thanks for the help, Trey - I appreciated it, even if you were massively camera shy. :-)

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Here's the shifter re-installed, complete with a brand new shift boot. That should help out a lot with keeping the noise and fumes out of the cab.

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I got a canopy courtesy of Craigslist - it was free because it has a busted out front window. It was originally slated to be used on the 1989 F150, but I found a better canopy for that truck and decided to use the black one on this truck. It'll help keep stuff from getting stolen out of the bed and keep things sort-of dry.

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Here's the engine compartment after I installed the vacuum distribution block, BP sensor, and decided on the rough location where the EFI wiring would enter the cab - the yellow tape marks that rough spot in both pictures. It's low and behind some stuff in the second picture, but you can see it just next to the factory wiring harness that goes through the firewall. The entire passenger's side of the firewall is being reserved for a future AC system installation.

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Here's the EGR spacer and the throttle body re-installed after having been cleaned. They look much better. The gaskets were Felpro #72543 for the EGR plate to upper intake manifold and #70262 for the throttle body to EGR plate. After bolting everything down, I even remembered to hook up the IAC, TPS, and EGR sensor.

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This is a picture of the firewall from the inside taken through the glove box opening - I removed the glove box to help see where the EFI wiring could come through the firewall. The rusty area is the backside of the pinch weld on the front of the firewall - as you can see it's got some rust issues. The second picture shows how bad - the bright spots in the red circle are daylight that you can see from the inside. I'm not doing a full restoration, but I will need to keep this at bay for a while. I think I'll use some Eastwood Rust Encapsulator on it followed by some seam sealer.

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EFI Conversion Information

This is the specific notes for the EFI conversion on this truck. I have a dedicated page for general information about doing a Ford EFI conversion.

I'm using a Mustang MAF-based EFI system for this conversion, circa 1989-1992. It's cobbled together from a variety of pieces I had laying around and that I collected from the local junkyards, eBay, and Craigslist. The computer is program code A3M, which is Mustang MAF unit for a manual transmission application.

The fuel tank, rear fuel lines, accumulator, filter, and low and high pressure fuel pumps are from a 1989 Ford F150 and a 1987 Ford F150 that I parted out. With the exception of the fuel sender being different, the later model tank is a direct bolt-in. See the EFI Gas Tank page for more details on the sender rebuild and installation process. I used the original later model nylon fuel fuel lines to go from the rear tank to the accumulator. The high pressure fuel lines from the accumulator to the high pressure pump and filter are custom made using the original nylon line connectors with 5/16" high pressure fuel hose clamped to them. I closed off the ports on the accumulator for the front fuel tank using a short length of low pressure fuel line and some clamps to keep dirt and debris out of the system, and prevent gas fumes from leaking out.

The later model EFI speed sensor mounts directly in the original transmission and uses the original speedo gear from the transmission. I used a 75" long speedo cable that, assuming I labeled all of my boxes of parts correctly, should be out of a 1987 F150 with a 5.0L and an AOD.

The wiring is mostly from a Mustang circa 1989-1992, but does have a few late model F150 bits spliced in where needed. The engine wiring is straight up Mustang, the engine compartment harness is a lightly modified Mustang harness with a custom adaptor harness plugged into it at the green, grey, and black connectors. The under-truck wiring to the speed sensor is from a 1987 F150, and the under-truck wiring for the fuel pump is a 1987 F150 frame harness reworked to remove non-essential bits.

I kept a complete to-do list as I went through this process.


Parts Replacement Information

Since I used parts from a couple of years to make this all work, I wanted to keep a note of it all in one place for later servicing.

  • The engine is a 1987 Mustang 5.0L.
  • The flywheel is originally for a 1985 F150 with a 302/5.0L, or more correctly that's the application I looked up to find the correct one. It's a 164 tooth unit that is drilled for the original 11" clutch for this truck and has a 50oz imbalance to match the later model Mustang motor.
  • The molded heater hose at the water pump is a Gates 18774. It's a 5/8" diameter molded hose with a S-bend in it, and one short and one long leg. The short leg needs about 1" trimmed off the end to make it work.
  • The radiator has previously been replaced by one from an AC equipped 1979 F100 with a 302, and the radiator hoses have to be from an AC truck as well. I know the upper radiator hose is a Gates 20860, which is the listing for a 1979 F100 with a 302 and AC.
  • The heater hose outlet in the front of the intake manifold is from a 1989 F150 with a 302/5.0L, but a few similar years are the same. This is where the temp sensor threads into along with the fitting for the heated throttle body setup, and it has a long horizontal extension for the heater hose outlet. I replaced the outlet fitting for the heated throttle body with a 90 degree fitting that has a 1/8" NPT male fitting on one end and a 1/4" hose fitting on the other. The original heated throttle body fitting on the manifold was a straight 3/8" hose fitting.
  • The rear gas tank, filler neck, and gas cap are out of a 1989 F150.
  • The fuel level sender is from a 1985 F150 with a 5.0L and EFI. This has the right EFI pump setup along with the correct early style fuel level sender. Any EFI swap of this kind will need a sender like this so that your original fuel gauge will continue to work.
  • The speedometer cable is a 75" long unit out of a 1987 F150 with a 5.0L and an AOD. Any comparably long cable with the right ends will work - there's nothing magical about this particular application.
  • The VSS is a standard Ford EFI unit out of a Mustang or F150. When I bought a replacement, I asked for one from a 1989 Mustang with a 5.0L and it worked fine. The original speedo gear was used on the new VSS. It's wrong due to the previous rear gear replacement, but it will get the speedo going until I can get a different one.
  • The charcoal canister is from a 1985 Mustang.
  • The AC system in/on/under the dash is from a 1977 F250, as is the condenser and receiver/dryer. The compressor is for a 1987 Mustang 5.0L. The hoses will start off as 1977 F250 pieces, but may need to be modified.


Parts for sale

  • Old 302 motor
  • Old flywheel (164 tooth, 28oz imbalance, accepts 11" clutch, recently resurfaced and in good condition)
  • AOD flexplate and motor plate (with inspection cover)


Purchasing Order

This was vehicle #32. This vehicle was my first EFI conversion project and the first vehicle I got in trade for another vehicle. It was also the first vehicle that I got that was owned by a friend previously - aka, the first one to move from a Foster Vehicle to one that I owned.

Comments? Kudos? Got some parts you'd like to buy/sell/barter/swap? Nasty comments about my web page so far? You can email Mike or Debbie.

Pretty much everything on this website is copyrighted, if you want to use something, ask first.

Page last updated 06/28/2009 01:44:19 PM