Older diesel vehicles using the SAE J1708 bus (with J1587 protocol) can be retrofitted with modern SAE J1939-based dashboards and instruments by using specialized protocol gateway converters. These devices bridge the hardware (RS-485 vs. CAN) and data-format gap between legacy J1708/J1587 engine networks and new J1939/CAN networks. Below, we survey several commercially available J1708→J1939 gateways (as of mid-2025), focusing on products suited for in-vehicle fleet retrofits. We compare their technical features – supported protocols, form factor, power range, ruggedness, interfaces, configuration tools – and note whether they operate unidirectionally or bidirectionally and support concurrent network monitoring. Direct links to official product pages or datasheets are provided for each solution.
Overview of Gateway Devices
To assist with high-level comparison, the following summarizes key specifications of the gateway devices discussed. All listed products are currently available from reputable manufacturers and intended for vehicle installation.
Below, we provide detailed descriptions of each product, along with direct links and technical highlights to aid in decision-making.
Axiomatic AX140400 Protocol Converter (J1587/J1939 Gateway)
Figure 1: Axiomatic AX140400 Protocol Converter.
This rugged module is an isolated J1587–J1939 gateway from Axiomatic Technologies (a manufacturer known for heavy-duty mobile electronics). The AX140400 converter features two isolated CAN 2.0B ports and one isolated RS-485 port, bridging up to two SAE J1939 networks and one SAE J1708/J1587 bus. It is built for harsh engine bay environments: an IP67-rated aluminum enclosure with an integral 12-pin Deutsch automotive connector and fully potted electronics. The unit operates from 9 V to 36 V DC (12 V/24 V nominal) and is rated for –40 °C to +70 °C ambient, with surge and reverse-polarity protection on the power input.
Supported protocols: The Axiomatic converter’s CAN ports support SAE J1939 (and even CANopen on other models) and the RS-485 port supports SAE J1587 or Modbus RTU. The model AX140400 comes with standard firmware for J1708/J1587 ↔ J1939 data exchange. This means it can be configured to translate messages in both directions – allowing legacy J1708 engine data to be broadcast on J1939, and potentially sending J1939 data (or requests) onto the J1708 bus if needed (e.g. for certain controls). The gateway can also simply listen on both networks for monitoring purposes. Its dual CAN interface is useful if the retrofit requires isolating the new dashboard’s CAN from other vehicle CAN traffic, or interfacing with two CAN networks simultaneously.
Integration and configuration: The AX140400 is highly configurable via Axiomatic’s Electronic Assistant software (a Windows PC application). Using a USB-CAN adapter, an integrator can map J1587 parameters (PIDs) to J1939 parameters (PGNs) or vice versa, set conversion scaling, message rates, etc., to tailor the device’s behavior to the specific engine and instrument cluster needs. (By default, the unit comes with a basic pre-programmed logic for J1708–J1939 data exchange, but custom programming is possible.) Axiomatic provides documentation and a library of J1939 parameter definitions to aid configuration. Because it is a fully featured protocol converter, it requires some technical expertise to set up, but offers maximum flexibility for handling proprietary signals or unusual data mappings.
Physical and other features: This device measures about 5.4 × 12.1 × 4.6 cm and weighs ~0.3 kg. It mounts via the sealed connector and/or brackets, and its robust design (EMC/CE certified, vibration-rated) suits off-highway and marine use as well. In summary, the Axiomatic AX140400 is a bi-directional J1708–J1939 gateway with an emphasis on ruggedness and configurability. It is ideal when a wide range of signals (including custom ones) must be translated and the user is able to configure the mappings using the provided software.
Technoton MasterCAN V-Gate (J1708 to J1939 Data Converter)
Figure 2: Technoton MasterCAN V-Gate module (J1708/J1587 to J1939 gateway).
The MasterCAN V-Gate is a compact gateway designed specifically for vehicle telematics and retrofit dashboard applications where a J1708/1587 network needs to feed into a J1939 CAN system. Developed by Technoton (a telematics equipment manufacturer), it focuses on merging legacy and modern vehicle data. The V-Gate listens simultaneously to an SAE J1708 data bus and an SAE J1939 CAN bus, filters and converts the J1708/J1587 messages into J1939 format, and then outputs the combined data on a CAN/J1939 line. This allows installers to upgrade dashboards or logging systems to J1939 without losing critical engine data from an older J1708-based engine.
Supported signals and operation: Because J1708/J1587 and J1939 define many analogous parameters differently, the MasterCAN V-Gate firmware is programmed to handle a pre-defined subset of the “most important” vehicle data parameters. It translates common engine and vehicle PIDs (speed, RPM, coolant temp, pressures, etc.) into standard J1939 PGNs. (Technoton provides a list of output PGNs it supports; users should verify that the needed signals are among those converted.) In essence, it adds a J1939 broadcast of key engine data on vehicles that originally lacked a CAN bus. Notably, the V-Gate can simultaneously read an existing J1939 stream (if present) and a J1708 stream – for example in vehicles that have both buses – and merge data so that one unified J1939 output is produced. The output CAN messages include both original J1939 data (if any) and the converted J1708 data, avoiding conflicts by using a configured source address for the gateway device. This merged output can be fed to a new instrument cluster, FMS telematics unit, or other J1939 device.
In addition to the CAN output, the MasterCAN V-Gate provides an RS-232/RS-485 port that can transmit the data in ASCII text or Modbus RTU formats. This is useful for telematics trackers or displays that don’t have a CAN interface – the gateway can directly supply them with engine data over serial lines (e.g. Modbus registers for fuel level, engine hours, etc.). Both the CAN and serial outputs operate simultaneously, so the V-Gate can feed a J1939 dashboard and, for instance, a GPS tracking unit at the same time.
Hardware and environment: The MasterCAN V-Gate is a very compact module (approx. 94 × 59 × 25 mm, 0.15 kg) and is normally installed in-cab or in a protected area. Its enclosure is IP40 rated– essentially protected from dust but not waterproof, so it should be kept out of direct exposure (a higher-IP version is not noted for this model). The device tolerates 10–45 V power input (suitable for 12 V and 24 V systems) and draws about 50–100 mA. It meets automotive E-mark standards for electrical safety and EMI. The V-Gate has dedicated connectors for the input buses and outputs: typically a plug for J1708, one for CAN in, one for CAN out, and one for RS-232/485 (the unit’s diagram labels these clearly). To avoid splicing into wires directly, Technoton even offers optional contactless readers (clamp-on couplers) for the J1708 and CAN lines – allowing “listen-only” installation without breaking the existing wiring.
Setup and usage: Technoton supplies a configuration and diagnostics software (“Service S6”) which connects via the device’s serial port. In general, the MasterCAN V-Gate is intended to work plug-and-play for its standard set of signals, requiring minimal user configuration. The Service S6 tool would be used to adjust settings like the output CAN identifier (address), baud rates, enabling/disabling certain PGNs, or configuring the serial output format (Modbus vs ASCII). Notably, if the installer needs to capture non-standard J1708 data or modify the mapping, this may be beyond the scope of the default device – the V-Gate is somewhat fixed to common parameters. Copperhill Technologies (a distributor) explicitly advises reviewing the supported PGNs list to ensure the needed data is included. Within its scope, however, the V-Gate “does exactly what it promises” – it provides real-time J1708-to-J1939 conversion with high reliability.
Overall, MasterCAN V-Gate is well-suited for fleet retrofit scenarios where a quick, pre-engineered solution is desired. It has been used in applications like upgrading trucks (Volvo, Renault, etc. from late 1990s) with modern telematics and combined CAN data streams.
CA Instruments TMT-7839 “Translator TB” (J1708 to J1939 Translator)
Canadian Automotive Instruments (CAI) offers the TMT Translator series, a popular plug-and-play gateway for mixing old and new engine data buses. The TMT-7839 Translator TB unit is designed to convert J1708/J1587 engine messages into J1939 CAN for newer dashboards, electronic gauges, or control systems. (CAI also produces a complementary TMT-3939 for the reverse direction or dual-CAN scenarios.) This product is often found in retrofit kits for truck engine swaps or instrument upgrades due to its ease of use and broad compatibility.
Capabilities: The TMT-7839 comes pre-configured to recognize a wide range of standard J1708 engine parameters (PIDs) – including vehicle speed, RPM, odometer, fuel rate, temperatures, pressures, etc., as well as diagnostic trouble codes – and to output their J1939 equivalents without user programming. In CAI’s words, it provides “real-time translation of a large assortment of performance parameters” and supports both 250 kbps and 500 kbps CAN baud rates to match the target J1939 network. This means whether the new dashboard (or other J1939 device) expects standard 250k (typical on-highway truck bus speed) or 500k (used in some newer or off-road systems), the translator can accommodate it. The device automatically handles message formatting, for example packaging J1587 data into the appropriate J1939 PGNs (including Transport Protocol for long multi-packet messages if needed). It also translates active fault codes: J1587 fault code data (PID 194) is converted into J1939 DM1 diagnostic messages so that the new dash’s warning lights and diagnostics will function. This comprehensive parameter support out-of-the-box is a key strength of the TMT-7839 – in many cases you can simply install it and immediately see engine data on the J1939 side.
Hardware and installation: The TMT Translator is a sealed polycarbonate module built to handle Marine, Truck, and Off-Highway conditions. CAI advertises it as durable and vibration-proof. The enclosure is not explicitly given an IP rating, but user reports and its use in marine contexts suggest it is weather-resistant (likely potted internally). The module has two LED indicators (power and bus activity) for status diagnosis. Wiring is straightforward: only 6 wires are needed to install it– typically: J1708+ and –, CAN High and Low, and power +12/24 and ground. (The device does not require an ignition signal or other inputs). The J1708 and CAN lines simply tap into the existing buses; the translator is mostly a passive listener on J1708 and an active broadcaster on CAN. The power input range is 9–30 V and it draws about 60–150 mA. Operating temperature is specified from –40 °C up to ~80 °C, covering automotive extremes.
One notable feature: the TMT-7839 includes a built-in USB interface (USB Type B) for connecting to a PC. Using CAI’s free ToolBox software, installers can scan both the J1708 and J1939 buses to see what data is present, troubleshoot communication issues, and update the unit’s firmware if needed. This effectively allows the TMT device to double as a diagnostic adapter during installation – for example, you can verify that the translator “sees” the engine on J1708 and is transmitting expected J1939 PGNs, all through the PC interface. CAI provides lifetime technical support at no cost, which can be valuable during tricky retrofits.
Plug-and-play focus: A key point is that no custom parameter mapping is required or possible in normal use – the TMT translator is preloaded with logic to cover most engines. This greatly simplifies upgrades: “modules preconfigured from the factory, providing seamless plug & play installation”. In scenarios like an engine swap (putting an older engine into a newer truck chassis, or vice versa), the translator can restore communication so that gauges, cruise control, and even advanced functions work again. (In fact, CAI mentions opto-isolated outputs for brake/clutch/fan/cruise status – indicating the device can even help interface certain hardwired signals if needed.) The plug-and-play nature means unidirectional operation: a given unit either runs J1708→J1939 or J1939→J1708 (the hardware is the same but firmware differs). The TMT-7839 model specifically handles older-engine-to-new-dash (J1587 to J1939) conversion. If the opposite is required, one would purchase CAI’s TMT-3939 or similar module instead.
Use cases: Fleet retrofitters and service centers have widely adopted the TMT translator for projects like modernizing instrument clusters, engine control unit (ECM) upgrades, or adding telematics to legacy fleets. For example, one could install a J1939-based digital gauge set into a 2003 truck originally with J1708 – the TMT box would supply the needed engine data to the new gauges. It is also used in marine settings to link older J1708 marine diesels to NMEA2000 or J1939 bridge systems. With a 2-year warranty and strong support, this device minimizes the risk in critical retrofit projects. In summary, the CAI TMT-7839 Translator is a highly user-friendly gateway that trades off some flexibility for convenience: if your application’s data points fall within its extensive standard list, it offers a nearly drop-in solution to get J1939-compatible outputs from a J1708 source.
Au Group Electronics GW2 Gateway (J1708 to J1939)
Another option comes from Au Group Electronics, a smaller U.S.-based firm offering niche protocol converters. Their GW2-1708-1939 gateway is a device dedicated to adding a J1939 CAN network to vehicles that only have a J1708/J1587 data bus. This gateway is often used in older heavy-duty trucks or buses so that new J1939-based accessories (dash displays, logging devices, etc.) can be installed. Au Group’s GW series has been on the market for over a decade, and while less known, they provide practical solutions (including variants for other conversions like J1939-to-J1708, J1708-to-NMEA2000, etc.
Functionality: The GW2 translates a fixed set of 24 standard engine/vehicle signals from J1587 to J1939. The supported parameters include vehicle speed, engine RPM, odometer, engine hours, coolant temperature, oil pressure, turbo boost, throttle position, engine load, various temperatures (fuel, oil, intake air), battery voltage, fuel rate and economy, PTO status, cruise control status, road speed limit status, idle shutdown status, and retarder/brake assist status. Essentially, it covers the essential instrumentation and engine performance data that a typical dashboard or telematics system would need. Each J1587 PID is mapped to the corresponding SPN/PGN in J1939 (for example: J1587 “Road Speed” (PID 84) is sent out as J1939 Wheel-Based Vehicle Speed in PGN 65265). These mappings are built-in and cannot be changed by the user – the GW2 is very much a fixed-function unidirectional translator. It does not send data from J1939 to J1708, and it will ignore any J1939 messages other than possibly those it needs for timing or address claiming. (For the reverse direction, Au Group sells a separate GW3 unit.)
Because the GW2’s outputs are pre-defined, using it is straightforward: once powered and connected, it immediately starts broadcasting the J1939 PGNs (at default cyclic rates) whenever valid data is seen on the J1708 side. The conversion latency is on the order of milliseconds, effectively real-time for dashboard purposes. One limitation is that if a less-common PID is needed (not in the list of 24), the GW2 will not translate it – so one should verify the engine’s critical data is within those supported.
Design and connectors: The GW2 is a very small module – only ~3.1 × 1.7 × 0.8 inches (78 × 42 × 21 mm) – and it comes in a black plastic enclosure with a translucent red cover (so you can see the status LED). It uses DB9 connectors for its interfaces: one DB9 male port for the vehicle network and power, and one DB9 female port for an RS-232 link. The DB9 “BUS” port carries J1939 CAN High/Low, J1708 A/B, +V supply, and ground on specific pins (Au provides a pinout diagram). This is convenient because it can plug directly into diagnostic adapters or use standard J1939 cable harnesses. The RS-232 port is primarily for monitoring and firmware updates – for example, an installer can connect a laptop and use a simple terminal to see that data is flowing, or use Au’s bootloader tool to update firmware if provided. The RS-232 could also output debugging info (like reporting what PIDs are detected), though in normal operation it’s not streaming the engine data in human-readable form (unlike the Technoton’s dedicated telematics output).
The GW2 is specified for 10 V to 32 V input (works on 12 V or 24 V systems) and draws about 65 mA normally. It can survive transients and has onboard surge protectors (TVS diodes) on both the J1708 and CAN lines to shield against voltage spikes. The device can handle the full automotive temperature range (–40 to +85 °C). The standard version, however, is not waterproof – the DB9 connectors are not sealed. It’s intended to be mounted in a dry location (e.g. behind the dash). For applications requiring exposure to the elements, Au Group offers a “waterproof” version of the GW2 (suffix –SW) which has a potted enclosure and a 14-wire sealed pigtail harness instead of DB9 connectors. This rugged version carries a higher price but would be suitable for off-road equipment or externally mounted installations.
Installation and usage: Using the GW2 is as easy as wiring it in parallel with the existing J1708 bus and connecting the new J1939 device to its CAN output. It does not require any configuration software or parameter setup – truly plug-and-play. An example use case (described in Au’s documentation) involves a legacy engine ECU broadcasting speed and distance on J1708; the GW2 picks these up and transmits the appropriate J1939 PGNs so that a modern dash can display vehicle speed and odometer. Because the GW2 is passive on J1708 (it just listens) and acts as a transmitter on a new CAN segment, it typically doesn’t interfere with other systems. It’s possible to have multiple listeners on J1708 (e.g. the GW2 and a diagnostic scan tool at the same time), and the new J1939 network can be isolated or tied into an existing CAN bus depending on the retrofit design.
One should note that the GW2’s J1939 output has no source address conflicts by design – since the vehicle originally had no J1939, the GW2 effectively becomes the sole ECU on that new bus (aside from whatever you connect to read the data). If connecting into an existing J1939 bus, the GW2 will use a fixed source address (likely 0xAE or similar) that should be chosen to avoid conflicts with other ECUs; however, in most retrofit cases it’s outputting to a dedicated link to the new instrument cluster or device.
In summary, Au Group’s GW2 gateway provides a cost-effective, simple solution for J1708-to-J1939 conversion with a known set of signals. It is less flexible than the Axiomatic or CAI solutions (no custom mappings or dynamic config), but for many standard diesel engines it covers the needed parameters. The availability of a sealed version broadens its use to harsh environments. This device is unidirectional (J1708 → CAN only) and aimed at retrofits where quick installation and reliability are more important than extensive configurability.
Conclusion
Retrofitting a J1939-based dashboard or control system onto a J1708-era engine is made feasible by the range of J1708-to-J1939 protocol converters now on the market. The choice of gateway depends on the specific needs:
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For a plug-and-play retrofit covering all common engine data with minimal setup, devices like the CA Instruments TMT-7839 Translator and Au Group GW2 are attractive. They come pre-loaded to handle standard parameters (24+ signals) and require little to no configuration. The CAI unit offers a more comprehensive parameter set (including fault codes) and USB diagnostic features, whereas the Au GW2 focuses on the essentials at a lower cost, with an available waterproof option for tough environments.
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For advanced or custom integration, the Axiomatic AX140400 provides a robust, bi-directional platform. It is ideal if you need to map proprietary signals or integrate the gateway into a complex CAN architecture (thanks to its dual CAN ports and PC configurable logic). Its industrial-grade build (IP67, heavy-duty approvals) suits extreme conditions.
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For telematics-oriented projects or merging data from multiple buses, the Technoton MasterCAN V-Gate offers a unique solution by outputting both on CAN and serial simultaneously. It automatically merges legacy and modern data and can feed downstream systems in parallel, which is great for fleet tracking installations. It is essentially uni-directional (J1708→) and has a fixed PGN set, so its simplicity is an advantage when those PGNs meet your needs.
In all cases, these gateways are commercially available as of mid-2025, with manufacturer support and documentation in English. They are purpose-built for in-vehicle retrofit integration, featuring automotive power conditioning, temperature tolerance, and protection features to ensure reliable operation in trucks, buses, off-road machines, and marine vessels. When selecting a gateway, consider whether bi-directional translation or plug-and-play simplicity is more important for your project, and verify that the device supports all the critical parameters for your engine and dashboard. With the right gateway in place, even decades-old diesel engines can successfully communicate with today’s J1939-based displays and controllers, extending the service life of legacy fleet equipment.
Sources:
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Axiomatic Technologies – “Protocol Converter, 2 SAE J1939, J1587, Isolated” (Product Page & Datasheet)
axiomatic.com
products.axiomatic.com -
Copperhill Technologies – “MasterCAN V-Gate – SAE J1939 & SAE J1708 to SAE J1939 Gateway” (Product description)
copperhilltech.com
copperhilltech.com -
Technoton (JV Technoton) – MasterCAN Data Converter (Product literature and specs)
jv-technoton.com
jv-technoton.com -
Copperhill Tech Blog – “J1708 to J1939 Conversion Made Smarter” (W. Voss, May 2025)
copperhilltech.com
copperhilltech.com -
Canadian Automotive Instruments – TMT-7839 Translator (Product info & brochure)
c-a-i.net
shop.cainstruments.com -
CA Instruments – TMT Translator User Manual (Electrical specs)
c-a-i.net
c-a-i.net -
Au Group Electronics – “GW2: J1708 to J1939 Gateway” (User manual/features)
auelectronics.com
auelectronics.com -
Au Group Electronics – GW2 Product Page (Supported signals list and options)
auelectronics.com
auelectronics.com
SAE J1939 has emerged as the de facto industry standard and preferred vehicle network technology for off-highway machines, including those used in construction, material handling, and forestry. Built on the Controller Area Network (CAN) protocol, J1939 serves as a higher-layer protocol that enables serial communication between microprocessor-based systems—known as Electronic Control Units (ECUs)—in heavy-duty vehicles.
These ECUs exchange a wide range of operational data, such as vehicle road speed, engine torque requests from the transmission, oil temperature, and much more, ensuring seamless coordination and efficient system performance.
The information presented in this book is primarily based on two key documents from the SAE J1939 Standards Collection:
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SAE J1939/21 – Data Link Layer
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SAE J1939/81 – Network Management
A Comprehensible Guide to J1939 is the first publication outside the official SAE standards to provide an in-depth yet accessible explanation of the J1939 message structure and network management. It combines technical precision with a clear, reader-friendly approach, making it an essential resource for engineers, developers, and technicians working with heavy-duty vehicle networks. More information…
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