Diesel Swap Considerations
It is fun to daydream about that swapped diesel engine you worked so hard to transplant fire up for the first time. When the starter disengages and the truck rocks with the rhythmic torque that could put a teething baby to rest.
Before you hit that point of the journey you have a few hurdles to jump. We here at Diesel Conversion Specialists® have compiled a list of things to be aware of when you set your sights on that diesel swapping adventure. This is not a list of everything you may stumble across, but it does give you a good understanding of what is to come.
Fuel System
- Will you be utilizing the factory fuel pump or an aftermarket pump?
- Fuel line connections very. The aftermarket industry is usually AN style friendly. You can typically acquire fittings that will adapt common fuel connections to AN.
- Ensure the fuel line ID is capable of handling new flow rates.
- A fuel return system may not currently be a part of your fuel system. This may require tank modifications.
- Filler neck replacement or modification to accept the larger nozzles used on diesel pumps at fuel stations will be necessary if your vehicle was originally equipped with a gas engine.
- Fuel sender modifications like capping off existing lines, terminating factory fuel pump, and sealing electrical connection should be addressed. You will want to retain the sender unit and wiring, so your fuel gauge still operates.
Exhaust System
- Be selective about what exhaust manifold you use so you can put the turbo in a friendly spot for the conversion. You can get a manifold that has threaded ports for temperature sensors.
- The turbo oil supply and drain tube may differ depending on manifold selection. Be mindful of bends in the drain tube so you do not restrict the flow of oil.
- The exhaust down pipe and how it attaches to turbo will likely need to be changed to a more conversion friendly version.
- What is your preference on how you hang the exhaust? You will most likely not be able to use existing hangers.
- What exhaust size do you have room for, and what modifications are you willing to do to get the exhaust you desire?
- What decibel level do you prefer? What will achieve that desired sound: muffler, resonator, or straight piped?
- Be mindful of the heat sensitive areas near drivetrain components.
- When modifying crossmembers and supports, leave room for exhaust routing.
- Be mindful of points where the exhaust could touch the cab or frame, as it will result in unwanted vibrations and resonate unpleasantly.
Transmission
- Manual or automatic?
- Can the transmission handle the diesel engine as well as the type of work it will be used for?
- Will there be enough room for the transmission selected?
- How to control your automatic transmission: Can the factory TCM be programmed or use an aftermarket standalone module and harness?
- What is the cooler line routing and transmission cooling capacity needed for the type of work the truck will be used for?
- Hard line cooler connections or rubber hoses?
- What type of fittings are needed?
- What is your preferred torque converter or clutch capabilities?
- How easily can the transmission be removed or installed for future repairs?
- Will the factory cross member support work and will the driveline angles be correct?
- The angle of the transmission will affect the pitch of an engine fan to the radiator. This will affect the air flow through the radiator and could be parasitic to cooling efficiency.
- Automatic transmission shifting via linkage or cable is nice to have routed or at least been thought about before final engine placement.
Transfer Case
- There are several transfer case options to choose from. Some things to consider are: chain or gear driven, cast iron or aluminum, divorced or married.
- How do you want to engage the 4WD in your vehicle? There is a wide selection of mechanical and electrically engaged cases to choose from.
- There are some options to make an electrical shifting case mechanical depending on case selected.
- Will it fit between the frame rails, can or should it be clocked?
- If mechanical engagement: will you use cable or linkage?
- Does the input shaft match transmission output?
- Will there be enough clearance between the front driveshaft and the transmission selected?
Drivelines
- Shortening and/or lengthening of the driveshaft may be necessary.
- Is the driveshaft capable of new torque capabilities?
- Now is a great time to address hanger bearing and u-joint condition. Starting fresh could save you some trouble shooting after the build. People tend to pay closer attention to vibrations and noises after investing so much into a build.
- Verify driveline angles to extend u-joint life and reduce unwanted vibrations.
Differential
- Know what gear ratios the truck is equipped with (example 3.55, 3.73, 4.88, etc.). Gears greatly affect drivability.
- Can the differential handle the desired torque and type of work you’re building the truck for?
- Does it need shims to change the driveline angles?
- Tire sizing may assist you in achieving your desired speed to RPM ratio.
Suspension
- Is your suspension ready for the weight of a diesel engine?
- Will you require a lift via suspension or body to aid in engine fitment?
Power Steering
- Electric over hydraulic or hydraulic system?
- Heavier engines and tire sizing affect the workload of steering components.
- Do you now require more cooling capacity than what the vehicle came with due to higher steering demands?
- Is the power steering pump going to be incorporating hydra-boost for braking?
- Power steering hoses will need to be made to handle high hydraulic pressures.
- Fittings will need adapting. AN fittings are usually supported in the aftermarket industry.
- The power steering pump reservoir could be mounted directly to the pump or remotely. If you use a remote reservoir, be selective in placement so you do not starve the pump of oil.
- A good time for a refreshed gearbox is while everything is out of the way.
Cooling Pack
- Is your existing system capable of supporting diesel engine cooling demands?
- Will you be using a viscous, electric, or electro-viscous engine fan?
- Will the fan you have fit the set space provided?
- Fan shrouds aid in safety as well as increase cooling capabilities. It is advised to retain that feature of your vehicle.
- Charge air cooler (CAC) systems take up a lot of room, so heavy modifications to the cooling pack occur when a system was not previously in place.
- It is often necessary to modify the core support for an adequate cooling pack to be installed.
- Radiator inlets and outlets differ greatly in location and size and will usually require custom hoses to get the system connected.
- Transmission cooling often routes into the radiator as well as a separate cooler for HD transmissions.
- The grill is often modified to make room for the added cooling components.
- The use of isolators on radiators, CAC’s, oil coolers, and condensers should decrease vibrations through cooling packs and extend the life of components.
- What pressures will the charge air system have? Make sure the components that make up the system can handle it.
Vacuum System
- Vacuum pumps are an accessory for most diesels and are not automatically included with each engine option.
- Older vehicles used vacuum air to operate HVAC systems as well as the brake booster. In some cases, the 4x4 lockers are vacuum actuated. So, keeping a vacuum system in place may be necessary.
- If vacuum is required, your options are typically an electric pump or engine driven accessory pump.
HVAC System
- What A/C compressor will you use?
- How will you adapt to the trucks A/C system, and what fittings will you require?
- A typical conversion uses the electrical system that vehicle already had in place, so factory operation can be retained.
- Sometimes a universal condenser will be used to allow for more room in the cooling pack.
- Proper system care is crucial to component reliability. High pressures and tight tolerances make the A/C system vulnerable to failure when proper care is not taken.
- Proper equipment for extracting and filling the A/C system is required. If you do not have all the necessary equipment to properly charge the system, it’s highly recommended that you take it to a local shop to be serviced.
- Keep the directional flow of the coolant through the heater core the same. Be aware of what you will need to make the connections.
- Know where on the engine to plumb your heater core lines. Make sure any rub and high heat points are addressed in the routing.
- A great time to flush or replace a heater core is while the engine bay is clear and accessible.
Starting & Charging System
- Depending on the transmission you use, the starter may differ from what the vehicle was originally equipped with.
- Starting circuits are not standard on stand-alone wiring options to allow for a more universal fitment.
- Battery and alternator wiring are not included in stand-alone harnesses and often rely on the existing system from the vehicle to operate.
- Conversion friendly one wire alternators are a common selection when doing a diesel swap. Many times, you can get a tachometer signal from the alternator as an output signal option.
- Some newer electrical systems require a handshake amongst the modules before being allowed to start.
- Anti-theft starting inhibiting parameters may also be in place and should be addressed before trying to turn over the engine.
- Jumping from the starter solenoid on some vehicles will result in an ECM lockout and the ECM will have to be unlocked before any further diagnostics can be done.
Cluster
- Oil pressure and coolant temperature sensors usually go directly to the cluster. You will use the vehicles factory sensors if you keep the factory cluster in most cases.
- Auxiliary gauges often come with sensors to wire in separately if you are looking for an aftermarket option.
- If your swapped engine has OBDII communications, some aftermarket clusters can use the CAN bus system to communicate cluster inputs for gauges.
- How will you get your tachometer operational: via alternator, crankshaft signal, CAN bus signal? There are aftermarket modules designed to adjust the input signal to a more applicable output signal giving you accurate gauge readings.
- The speedometer input may need to be addressed if not fed from the differential. Modules to drive a cable or change the speed signal are available.
- The check engine light may be on depending on the vintage of vehicle.
Cruise Control
- On cable driven throttles, this can be a cruise servo using a cable to control throttle.
- Drive by wire systems add a level of complexity. A good understanding of electrical operations along with clear schematics is the minimum requirement when tackling this part of the vehicle’s operation.
- There are aftermarket options available if factory cruise control is not easily adaptable.
Module Communication
- A scan tool with code reading capabilities is required for diagnosing vehicles with OBDII capabilities.
- Transmission tuning will require the builder to upload and download transmission tuning files to get the transmission to function properly with the newly selected engine.
Emissions
- Is your combination going to be compliant with the emission requirements in your area?
- What are your local emission requirements? Testing?
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