1989-1993 Dodge 5.9L Cummins Transmissions & Parts

Transmissions on the 1989-1993 RAM 5.9L Cummins

Dodge backed the first-gen Cummins with three gearboxes. The Getrag G360 5-speed manual ran all five years, geared 5.53/3.02/1.60/1.00/0.77 with a 5.03 reverse. Automatic trucks built from 1989 to mid-1991 got the A727 TorqueFlite, a heavier-duty 3-speed with no overdrive and a non-lockup torque converter. In mid-1991 the A518 4-speed took over on the D250, D350, W250 and W350, adding a 0.69 overdrive and converter lockup. Its 1-2-3 shifts stay hydraulic, while overdrive and lockup are switched by electronic solenoids. Under Chrysler's 1992 naming the A518 became the 46RH (and the A727 the 36RH), so a 1992-1993 automatic may be listed under either name. Capacities tell you what you are servicing: the G360 holds 3.5 quarts of motor oil, and the A518 takes 14.5 to 16.5 quarts of ATF+4.

What fails and why

• G360 input bearing. The upper input bearing is the manual's weak spot. Heat, vibration and load from extended towing raise fluid temperature and starve that bearing. Listen for a whine or growl in neutral with the clutch out that changes when you press the clutch, then roughness under load and, left alone, gear damage.
• Clutch slip. On manual trucks, engine rpm that climbs without road speed under load means the clutch is slipping. The stock clutch is undersized once fuel has been added.
• A518/46RH converter and clutches. Behind the Cummins the A518 is the weak link, especially at mid-to-high mileage and with a trailer: slipping, a flare on the 2-3 shift, converter shudder and overheated fluid. One documented 1993 D250 that reached 620,000 miles went through two remanufactured A518s before a converter failure, and it only held up after a rebuild with a low-stall non-lockup converter, more clutches in the overdrive and direct packs, a new second-gear band and a billet accumulator piston.
• A727 heat. With no overdrive, the 3-speed cruises at high rpm and runs hot, and its converters were loose by design to make the driveline last longer.
• Cooler lines. The factory steel lines rust and leak. ATF drips under the passenger side, a low level and burnt fluid are the signs.
• Kickdown cable. A cable that is mis-set or disconnected after throttle-linkage work gives early, soft shifts and low line pressure, and that can burn the transmission up.

Stock replacement vs. upgrade

If the truck is stock and works for a living, start with service and cooling. The A727 schedule is fluid, filter and a band adjustment every 24,000 miles or 24 months, and the G360 gets a drain and refill every 60,000 miles. Owners who tow add auxiliary cooling, either a factory-style under-bed cooler with a fan or a large aftermarket core, plus a deep pan. Past that, the automatic upgrade path is a better converter, more clutch capacity and a valve-body kit; aftermarket non-lockup converters for these trucks aim for a stall suited to street and towing, quicker response at lower rpm and less heat. Manual owners move to a stronger clutch, and the NV4500 5-speed is the common replacement for a worn G360. Built first gens have gone further, to the 47RH, 48RE, Allison 1000 and G56, but those are custom swaps.

What we carry

Start with fluid: Hot Shot's Secret Blue Diamond and ADRENALINE transmission fluids plus its Shift Restore additive, and Lucas Oil multi-vehicle ATF. For cooling, Mishimoto supplies universal transmission fluid coolers, a heavy-duty cooler with its own fan and a combination transmission and power steering cooler. Deep pans come from PPE, Mag-Hytec (727-D deep and 727-DD extra deep), BD Diesel (deep sump) and XDP (XD450 aluminum), with a MAHLE pan gasket, a Mag-Hytec pan filter and an ATS drain plug made for ATS pans and differential covers. Hard parts include the BD Proforce torque converter and BD valve body, the ATS Diesel Performance A618 towing valve body and 618 master rebuild kit, and an XDP flex plate bolt kit. If the case itself is done, BD has a complete 518 4WD transmission and ATS a complete 618 transmission package.

Fitment notes

Identify the transmission before you order. A 1989 through early-1991 automatic is an A727 3-speed; the A518 4-speed only shows up from mid-1991, yet parts sellers list 727, A518 and 46RH together for all of 1989-1993. Product dates here vary: the BD converter is listed for 1989-1993, the BD valve body and complete 518 for 1991-1993, and the ATS valve body and transmission package for 1990-1993. Count the forward gears, look for overdrive and confirm against your VIN. The BD complete transmission is a 4WD unit, so it belongs under a W250 or W350. Planning an exhaust brake on an A518/46RH? It needs a converter lockup controller; the non-lockup A727 does not. And if a previous owner already swapped in an NV4500, buy parts for that unit, since a G360 clutch is built for the stock input shaft.

Frequently asked questions

Which transmission does my first-gen Cummins have?

If there's a clutch pedal, it's the Getrag G360 5-speed, used all five years. Automatics built from 1989 to mid-1991 are A727 3-speeds with no overdrive; mid-1991 through 1993 automatics are the A518, called the 46RH from 1992. Because the change came mid-year, a 1991 truck can be either, so count the gears and check your VIN.

What goes in the G360 manual?

Motor oil, not gear oil or ATF. The spec is 3.5 quarts of 5W-30, drained and refilled every 60,000 miles. Many owners who tow run 15W-40 and add an extra quart to protect the input bearing; that's owner practice, not the factory number.

Is the A518 strong enough behind a stock 5.9L?

It can live, but it's the weak link, especially with towing and miles. Diesel Hub notes it was short-lived in Cummins trucks because the 1994 P-pump engine needed a more robust unit. Keep the fluid cool and clean, watch for slipping or a 2-3 flare, and plan on converter and clutch upgrades when it comes apart.

Do I need an extra transmission cooler?

If you tow with an automatic, it's the first thing to add. First-gen owners who tow run an under-bed cooler with a fan or a large aftermarket core, usually with a deep pan. Some trucks left the factory with an external auxiliary cooler, so look before you buy, and check the factory steel cooler lines for rust while you're under there.

Why does my automatic shift early and soft?

Check the kickdown cable first, especially if anyone has worked on the throttle linkage. A mis-set or disconnected cable makes the transmission upshift early with low line pressure, and that can burn it up. Set the cable before you blame internal parts.

Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.