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1999-2007 Ford 5.4L or 6.8L

Posted by Diesel Conversion on Oct 15th 2020

Many times customers ask about converting 1999 - 2007 Ford ® 5.4 and 6.8 trucks to a diesel due to the fact that they can be purchased reasonably, or they already have one and would like diesel power. There is not too much difficulty with this conversion, as these trucks will accept a diesel Super Duty intercooler without modification and the frame and transmission mounting is the same as the diesel versions. You should plan to drop the fuel tank and remove the electric fuel pump. This is explained further in the installation manual. Keep in mind that a new diesel exhaust system is recommended and a diesel radiator is also a good idea if you plan to do some considerable hauling.

It is recommended that a F-250 or heavier duty chassis be selected for 6-cylinder conversions, as the F-150 chassis is really too light duty to handle the power and weight of the 6-cylinder Cummins ®.



The 4R100 transmission in the gasoline trucks are a fine transmission.  If you are planning on doing constant heavy pulling or adding a lot of performance upgrades to your Cummins you may want to have your transmission rebuilt with aftermarket parts.

The 5R110 is not considered a "conversion friendly" transmission due to the limitations of aftermarket transmission control modules.  If your gas powered truck already has a 5R110 equipped it is highly recommended to switch to a 4R100 transmission!

Ford 5-Speed 
– Diesel Conversions ® currently does not make a 5.4 or 6.8 5-speed adapter plate due to the small clutch that would have to be used. We may someday for 4BT conversions. We make adapter plates for 5 speed transmissions as long as they were behind a 7.3 diesel or a 460 big block. The 1995 and newer transmissions are rated for 470 ft. / lbs. of torque.

Ford 6-Speed – Diesel Conversions ® currently does not make a 5.4 or 6.8 6-speed adapter plate due to the small clutch that would have to be used. We make adapter plates for the 7.3 and 6.0L diesel 6-speed. These are very good transmissions for the conversion, and worth the upgrade.



Our adapter plate kit uses the 6.0L Ford Power Stroke ® starter. This is actually the same adapter that was designed for the 6.0L 5R110 automatic transmission but it also works for the 4R100, and allows you to upgrade in the future if you'd like. Two holes in the top of the adapter are not used (the 4R100 does not have these holes, and two in the bottom are not used either, or if you want to use them drilling out the threads in the bottom holes in the transmission is required. The adapter plate replaces the adapter already on the back of the Cummins engine, making a factory quality connection for the transmission. They are precision machined from aircraft grade (6061) aluminum.


Our motor mounts are pre-drilled to accommodate for the stock engine fan (recommended). Because the Cummins engines are longer this will move your transmission back 2” to 3” causing you to move your transmission cross member back. The engine mounts are an excellent design with a bolt going all the way through the isolator, instead of relying on rubber and weak interlocking tabs to secure them to the frame cross member.

It is necessary to move the transmission cross member back or lengthen the slots in the mount to slide the transmission back enough to give room for the engine driven fan. Automatic trucks already have holes in the frame to move the cross member back to accommodate the Dodge Cummins engine driven fan.  You will need to shorten your rear driveshaft about 1.5". The front driveshaft has a longer slip yolk and is long enough unless you have a lifted truck, then you'll likely need to lengthen the front shaft.


Bushing kits include our custom built adapters to put your Ford gauge sending units into the Cummins engine so that your stock gauges still work with the Cummins engine.


When using Dodge Cummins alternator we provide you with an external voltage regulator. Common Rail applications do not need the external regulator.


Our conversion friendly manifolds work much better in the conversion for the 12-valve and 98.5-02 24-valve engines. These manifolds place the turbo in a better place for a/c component clearance than the stock variety, and also make exhaust and turbo oil drain connections easier as well. The conversion friendly manifolds improve air flow over stock and are 2-piece to prevent cracking.

12-Valve Engines

When using a 12-valve engine for your conversion with one of our manifolds it is required that the housing of the turbo be re-oriented so oil feed and drain are vertical. Once the housing is re-oriented, the waste gate actuator will interfere with the engine block. To remedy this issue, we offer a conversion friendly waste gate actuator kit (DCS Part Number 3048) to fit the H1C and HX35 Turbos that came factory on the 12-valve engines.

24-Valve engines

When using a 24-valve engine for your conversion with one of our manifolds we recommend upgrading to a 2003-2004 Common Rail or similar style turbo . Due to the design of the waste gate actuator on the stock 24-valve turbo it makes it difficult for the housing to be re-oriented. Using a 2003-2004 common rail turbo alleviates this issue.


Along with replacement manifold gaskets, hardware, and turbo mounting studs, we also offer a flexible turbo drain tube that connects to the stock hose and elbow that is left in your engine block when the stock drain tube is removed. The flexible drain tube makes for an easy connection to the re-oriented turbo housing.


The tach kit consists of three parts; the Mounting Bracket, Sensor, and Tone ring. These parts are necessary to make your factory tachometer work.

 Providing this signal to your Ford PCM computer also is necessary for the air conditioning, transmission temperature, and other gauges to function properly. All 5.4L and 6.8L trucks require the tach ring that bolts onto the front of the Cummins crankshaft balancer for the sensor to send the correct signal pulse to the Ford PCM which makes the tachometer work.

 It is not necessary to buy a diesel instrument cluster for your truck.


See the Automatic Transmission Article for more information.


Our air filter kit includes a Brute Force air filter, pipe and hose to connect to your turbocharger. We offer two styles of air filter kits. The kit the 5.4 or 6.8 liter truck will most likely use is the DCS SKU 1941. It requires relocating the passenger side battery to the driver’s side. This takes some fabricating skill to make the brackets to mount the passenger side battery tray and another one just like it on the driver’s side, but it provides a nice roomy area for the air filter, and allows you to keep the degas (radiator fill tank) in its stock location.

The DCS SKU 1943 positions the Brute Force air filter between the passenger side battery and the radiator. This is especially the kit to use if you are using a Ford 6.0 diesel radiator and a common rail style turbo.

A/C Line

The complete A/C line connects to a 1994-2005 Dodge compressor.  All you have to do is bolt the line to the drier and condensor, & refill the system.  It's that simple!


Diesel Conversions ® radiator hose kit includes the radiator and heater hoses that work well in the conversion and a specially bent aluminized steel lower radiator hose connector tube along with hose clamps. The kit that is offered in our kit builder for these trucks only works with the stock radiator and a new style water connections as shown on our Cummins Engine Information page.


Diesel Conversions ® can provide you 5.4 or 6.8L engine harness modification services that make wiring much less of a challenge. We modify your Ford engine harness to connect to a Cummins engine harness, providing your Ford PCM the signals it needs to make your factory gauges work. This service is normally included in our comprehensive kits.


Even if you buy everything Diesel Conversions ® sells, you will need to come up with a few parts on your own, such as an exhaust down pipe (usually a Dodge ® down pipe can be a good start), a diesel exhaust system for the same year and style of your truck, a Ford Super Duty diesel radiator and intercooler, and intercooler tubes (again Dodge stuff can be a good start). We may be able to supply you with these, but our supply is limited at this time. If you live in a colder climate, we would also recommend adding an additional battery for longer starter cranking ability.

Automatic transmission equipped trucks will require a throttle position sensor. Depending on the year and what transmission your Cummins engine had on it originally, you may need to purchase a throttle position sensor, or look into other options. All 24-Valve engines already have a throttle position sensor that can be used for the transmission controller.

Sometimes customers buy engines out of industrial applications. These engines may not have the correct brackets for conversion friendly accessories.
See Cummins Engine Information for more information .


Give us a call and find out how Diesel Conversions ® can do a professional conversion on your truck for a reasonable price. We have an international airport for travel from and back to our shop, and also can help with shipping options getting a disabled truck here.

This information is provided to you to help you make an informed decision on your conversion. If you have any questions do not hesitate to CONTACT US.

*Diesel Conversions ® is not affiliated with Cummins, Ford, or Dodge. Our use of these and other registered trademarks is for descriptive purposes only.

Diesel Conversions ®
Diesel Conversion Specialists

Knowledgebase Topic:
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Adaptable Transmissions:
Ford 7.3 4R100 AT