47RH Won't Shift Into 3rd Gear: Why It Is Almost Never the Solenoids, and the Real Fix

47RH Won't Shift Into 3rd Gear: Why It Is Almost Never the Solenoids, and the Real Fix

47RH Won't Shift Into 3rd Gear: Why It Is Almost Never the Solenoids, and the Real Fix

You pull away from a stop, the 47RH grabs 1st, shifts to 2nd, and then nothing. The engine winds out and the truck stays in 2nd. Or it shifts to 2nd, hangs there, and finally thumps into gear only when you lift off the throttle. Reverse still works. The overdrive light behaves normally. So you buy a governor pressure solenoid, a transducer, or a full solenoid kit, install it, and the truck shifts exactly the same as before.

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That is the most common wasted repair on this transmission, and it happens because owners troubleshoot a 47RH as if it were a 47RE. It is not. Understanding one specific thing about how the 47RH is controlled will tell you, in about five minutes, whether you are chasing an electrical problem or a hydraulic and mechanical one.

What the 47RH is, and the detail that decides your diagnosis

The 47RH is the heavy-duty Chrysler four-speed built on the TorqueFlite architecture, with an overdrive unit added behind the main case. It went into Dodge Ram 2500 and 3500 trucks behind the 5.9L Cummins turbodiesel and the 8.0L Magnum V10. Gearboxlist places 47RH production in the 1993 to 1995 window, while DieselHub covers the broader 47RH and 47RE family as serving 1994 to 2003 Ram 2500 and 3500 trucks. Either way, if you have an RH, you have an early truck.

Per DieselHub, the gear ratios are 2.45:1 in 1st, 1.45:1 in 2nd, 1.00:1 in 3rd, 0.69:1 in overdrive, and 2.21:1 in reverse. Note that 3rd is 1.00:1, a straight-through direct-drive ratio. DieselHub lists max input torque at roughly 450 lb-ft with a Chrysler strength designation of "7" on a 1-to-9 scale, and Wikipedia's TorqueFlite entry gives the same 450 lb-ft (610 N·m) figure for the A618 family.

Now the part that matters. The letters in the name are not decoration. Wikipedia's TorqueFlite entry states that the RH designation indicates "hydraulic controlled governor pressure" while RE means "electronic controlled governor pressure." DieselHub's A518 page is blunt about what that means in practice: the "1, 2, 3 shift sequence is controlled entirely by hydraulic governor pressure," while "overdrive engagement and torque converter lockup rely on electronic solenoids." HGM Electronics describes the same split, noting that "the shifts between the first 3 gears need to be adjusted with the hydraulic governor" and that "activating overdrive and the torque converter clutch (TCC) engagement can be done electronically."

The five-minute test that saves you a solenoid

Follow that architecture to its conclusion. On a 47RH, the only two things a solenoid can do are engage overdrive and lock the torque converter. The 1-2 and 2-3 shifts do not pass through any solenoid, module, or connector. They are commanded by governor pressure, which rises with output shaft speed, working against throttle pressure.

So if your truck will not shift into 3rd, the electronics are not in the path. Confirming it is straightforward: unplug the transmission's main case connector and road test it. Losing power to the transmission will cost you overdrive and lockup, and will typically set codes, but the 1-2 and 2-3 shifts must still happen, because they were never electrical to begin with. If the truck shifts 1-2 with the harness unplugged and still refuses 3rd, you have proven the fault is hydraulic or mechanical. Stop buying solenoids.

Working the problem in order

  1. Fluid level and condition, on a hot transmission. Low fluid lets the pump aerate and drop pressure at exactly the moment a shift is commanded. Gearboxlist and DieselHub both specify Mopar ATF+4 (MS-9602). DieselHub lists 14.5 to 16.5 quarts dry fill and approximately 4 quarts for a service refill, so a pan drop moves only about a quarter of the fluid in the unit. Dark fluid with a burnt smell, or a pan carrying friction material, changes the entire conversation and points at a worn clutch pack.
  2. Throttle valve linkage. On these units the throttle valve cable sets throttle pressure, which works against governor pressure to determine shift points. A cable that is out of adjustment or seized can hold shift points so high the truck feels like it will not shift at all. This is a free check and it is the single most commonly skipped one. Our throttle valve cable adjustment guide walks the procedure.
  3. Line pressure test. Gauge it in each range and compare against spec. Pressure that is low across the board points at the pump, filter, or a leaking circuit. Pressure that is correct in some ranges and low in others narrows the fault to a specific circuit. The line pressure test procedure covers where to tap in and what the readings mean.
  4. Governor pressure. Because governor pressure alone times the 1-2 and 2-3 shifts on an RH, a governor that sticks or leaks will hold the transmission in a lower gear. It has to rise smoothly with road speed.
  5. Road test the failure mode precisely. There is a real difference between a transmission that never attempts 3rd and one that attempts it and slips. Flaring engine RPM as the shift is commanded means the shift is happening hydraulically but a clutch pack is not holding. That is a friction problem, not a control problem.

The likely causes, ranked

Throttle valve cable misadjustment. Free to check, free to fix, and it can produce a complaint that reads exactly like a no-3rd condition. Always first.

Low or degraded fluid, or a restricted filter. Cheap, and it protects everything downstream while you diagnose.

Governor or valve body circuit leakage. Wear in the valve body bores bleeds off the pressure a shift needs to complete. This is why valve body reconditioning kits exist for the 46RH and 47RH family in the first place.

Front, or direct, clutch pack wear. This is the expensive answer, and it is the one that a pan full of friction material or a flaring shift points toward. Raybestos Powertrain's steel clutch pack listing for the 1990 to 1997 A518 diesel application specifies "7 Front, 4 Overdrive Brake, 9 Overdrive Direct Steel Clutch Plates," with the front steels at .069" thick, 7.035" outside diameter, and 12 teeth. Those seven front plates are the stack that has to hold torque in direct drive, and when they are cooked, no amount of pressure correction upstream brings 3rd back.

The fix, and the parts that actually address it

If your pressure tests are good and the fluid is clean, fix the adjustment and the leakage. If the fluid is burnt and the shift flares, the unit needs to come apart, and once it is apart the front clutch pack, the front band, and the servo are all on the table.

47RH servo piston kit for Dodge Ram Cummins transmission
47RH Servo Piston Kit — fresh seals for the servo that applies the front band. A leaking servo seal bleeds off apply pressure and shows up as a lazy or incomplete shift.

A leaking servo seal is one of the classic reasons a shift will not complete on this family, and the kit is inexpensive relative to the labor required to reach it. Replace it any time the valve body or band is already out.

Replace while you are in there

Cost and effort

The realistic tiers look like this. A throttle valve cable adjustment is a driveway job measured in minutes and costs nothing but your time. A pan drop with filter, gasket, and fluid is a two to three hour job for a competent DIY mechanic, with the main consumable being the roughly 4 quart service refill of ATF+4. A valve body pull and recondition, with the servo resealed while you are in there, is a half-day job and is where a large share of no-3rd complaints are actually resolved. A full teardown to reach the front clutch pack means the transmission comes out of the truck, which is a full weekend for an experienced DIY builder or a multi-day ticket at a shop. Because the 47RH carries roughly a 450 lb-ft input rating and lives behind a Cummins, it is worth doing the clutch pack properly rather than doing it twice.

FAQ

Will a governor pressure solenoid fix a 47RH that will not shift into 3rd? No. On an RH transmission the 1-2 and 2-3 shifts are controlled entirely by hydraulic governor pressure, per DieselHub and HGM Electronics. The solenoids on this unit engage overdrive and lock the converter. A solenoid cannot cause, or cure, a missing 2-3 shift.

How do I know whether I have a 47RH or a 47RE? The letters tell you how governor pressure is controlled. Per Wikipedia's TorqueFlite entry, RH means hydraulic controlled governor pressure and RE means electronic controlled governor pressure. Early trucks are RH. If your diagnosis depends on it, confirm from the tag on the transmission rather than from model year alone, because the changeover does not fall neatly on a calendar boundary in every source.

My truck has no 3rd but reverse is fine. Does that rule out the clutches? No, and it is worth a careful road test before you conclude anything. A shift that flares engine RPM as it is commanded indicates the shift is occurring hydraulically while a clutch pack slips, which is a friction problem. A transmission that never attempts the shift at all points upstream, at throttle valve adjustment, governor pressure, or valve body leakage. Pressure test before you pull the unit.

Sources