47RE No Reverse: Diagnosis and Fix

A 47RE that pulls fine in Drive but will not back up is a case where Chrysler's service manual gives you a short, specific list of suspects. This is the heavy-duty four-speed behind the 5.9L Cummins and 8.0L V10 in 1996-2002 Ram 2500 and 3500 trucks. Reverse in this unit depends on four things: the front clutch, the rear (low-reverse) band and its servo, the overdrive direct clutch at the back of the case, and enough line pressure to hold all three. If any one of them lets go, the truck will not move backward, or it will creep back with the engine flaring.

Below is the factory diagnosis chart for this exact complaint, the pressure test that splits it, and the parts Sonnax and TransGo have documented as the usual failures in the 47RE. The specs come from Chrysler's 2001 Dodge Ram Truck (BR/BE) service manual. Sources are listed at the end.

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What the Factory Chart Says: No Reverse, D Ranges OK

The factory service manual has a diagnosis chart entry for exactly this condition, "No Reverse (D Ranges OK)." Per the 1998 Chrysler Ram Truck service manual (Group 21, 46RE/47RE), it lists seven possible causes, with the factory correction next to each:

1. Gearshift linkage or cable misadjusted or damaged. Repair or replace the linkage parts.
2. Park sprag sticking. The correction is to replace the overdrive annulus gear. The park pawl engages teeth on that gear, so a gear with damaged teeth can hold the pawl from releasing.
3. Rear band misadjusted or worn. Adjust the band, or replace it.
4. Valve body malfunction. Remove and service the valve body, and replace it if any valves or bores are worn or damaged.
5. Rear servo malfunction. Pull the transmission and replace the worn or damaged servo parts.
6. Overdrive direct clutch worn. Disassemble the overdrive unit and replace worn parts.
7. Front clutch burnt. Pull and disassemble the transmission and replace the clutch parts.

If the truck will not move in Drive either, you are on a different chart. The "No Drive or Reverse (Vehicle Will Not Move)" entry lists low fluid, a loose or misadjusted shift linkage, a broken U-joint, axle or transfer case, a plugged filter, a damaged oil pump and a valve body malfunction. Check the driveline before you blame the transmission. On a 4x4, the same page notes that a transfer case failure can plug the cooler.

Start With the Linkage and the Park Pawl

The first item on the list costs nothing to check, so check it first. Put the column shifter in R and crawl under the truck. The manual valve lever on the left side of the case should be sitting in its reverse detent, not between detents. If the cable is stretched or its bushing is gone, the manual valve can sit partway, and the reverse circuit never gets full line pressure. The same page of the manual lists a misadjusted cable as a cause of shifts that are delayed or harsh, so a sloppy cable usually shows up in more than one way.

The park sprag cause is easy to overlook. If the truck feels like it is dragging against something when you select Reverse, or it stays locked after you come out of Park on a grade, pull the overdrive unit and look at the teeth on the annulus gear. The manual's fix is the gear, not the pawl alone.

Figure Out Which Part Let Go

Every part that holds Reverse also works in some forward gear, and that overlap is what makes the 47RE easy to diagnose from the driver's seat. Here is where each reverse element also applies, from the manual's clutch and band application chart:

Reverse element	Also applied in	Road test to confirm
Front clutch	Third and fourth	Slips or flares on the 2-3 shift and in third
Rear (low-reverse) band	Manual 1 only	No engine braking coasting down a hill in manual 1
Overdrive direct clutch	Every range except fourth	No coast braking in manual 2 or 1

If third gear flares and there is no Reverse, the front clutch is burnt. Manual 1 freewheels on a closed-throttle downhill and there is no Reverse: that points to the rear band or servo. If coast braking is gone in both manual 2 and manual 1 and Reverse slips or is gone, look at the overdrive direct clutch. A truck with all forward gears solid and no Reverse at all usually has a band, servo or linkage problem, since those parts carry very little load in the forward gears.

The Rear Servo and the Reverse Servo Plug

Reverse is the highest-pressure range in the 47RE, and the rear servo takes that pressure on every backup. Sonnax lists "No Reverse" and "burnt bands" as the symptoms of a failed rear servo piston in this unit. According to Sonnax, the rear servo piston in '97-later 47RE and 48RE units can wedge in its bore, causing bind in Reverse, and that intermittent binding wears the bore and damages the band. The OE piston is cast, and it can crack.

Get the right piston for the year. Sonnax lists the '97-later 47RE/48RE piston as OE 52118745 and the '94-96 47RE/RH piston as OE 4531229. Both are 2.46 in. across. The 46RE and A727 piston is a different 2.80 in. part, so a 46RE piece will not fit a 47RE case.

The plug inside the servo piston is a second weak point. Sonnax explains that the 47RH/RE and 48RE use an extended-tip aluminum reverse servo plug. The smaller units use a flat-tip plug. Both are aluminum, and both wear, gall and break at the spring seat under Reverse loads. A broken plug means the servo cannot apply the band, and the result is no Reverse and a burnt low-reverse band. Sonnax sells a hardened steel replacement (kit 22912-01K) that fits both styles.

The Rear Band, Strut and Drum

The manual's correction for a misadjusted rear band is simply to adjust it, and on a 47RE that means dropping the pan. The factory procedure, from pages 21-308/309 of the 1998 Chrysler Ram Truck service manual:

1. Raise the vehicle, remove the pan and drain the fluid.
2. Loosen the band adjusting screw locknut 5-6 turns and make sure the screw turns freely in the lever.
3. Tighten the adjusting screw to 8 N·m (72 in-lb).
4. Back the screw off 3 turns.
5. Hold the screw and tighten the locknut to 34 N·m (25 ft-lb).
6. Install the pan with a new gasket, tighten the pan bolts to 17 N·m (13 ft-lb), and refill with Mopar ATF+4.

If the screw runs out of adjustment, or the band will not hold after you adjust it, the band or drum is worn. There is a trap here for a rebuilt unit. Sonnax warns that after the low-reverse drum has been resurfaced and the band relined, the band may not hold, and you get a slip or no Reverse. The stock strut is too short for the smaller drum. Their guideline, by measured drum OD:

• 6.185-6.200 in.: the OE strut is fine.
• 6.170-6.185 in.: use the extended strut that is 0.100 in. longer (Sonnax 22900-10).
• Under 6.170 in.: use the 0.150 in. longer strut (22900-15). If the band still will not apply, replace the drum.

If a freshly rebuilt 47RE has no Reverse, measure the drum before you pull it apart again.

The Overdrive Direct Clutch Spring

The overdrive direct clutch is applied by a large spring, not by oil pressure. TransGo, which makes a high-temp replacement (TFOD-SP, a direct replacement for OEM spring 4461027), says RE-family units often come in with faded direct clutch springs and burnt direct clutch plates. Once the spring fades, clamping force drops, and TransGo lists the complaints as slipping or no Reverse, reduced or no coast braking in manual 2nd or 1st, and burnt direct clutch plates.

The manual's correction for a worn direct clutch is to disassemble the overdrive and replace the worn parts. Replace the spring any time the direct clutch plates are burnt. Fresh plates behind a tired spring will slip again. You need a spring compressor to do it safely.

While the overdrive is apart, check the piston retainer. Sonnax says many OE supports in 46RH/RE, 47RH/RE and 48RE units do not seal well against the case. That cuts lube flow to the geartrain and can take out the reverse drum, retainer and planets. If you find a scored reverse drum, that is the likely reason.

Pressure and Air Tests Before Teardown

The manual is clear that the cause of a failure usually is not known until the hydraulic and air pressure tests are done. For Reverse, run Chrysler's Test Four. Put a 300 psi gauge on the rear servo port, with the rear wheels off the ground and the engine at 1600 rpm in Reverse. Rear servo pressure should read 145-175 psi and rise to 230-280 psi as the throttle lever at the valve body moves rearward, per the 1998 Chrysler service manual. Then compare it with the other tests, using the manual's pressure test analysis chart:

• OK in 2, low in R and 1: a leak in the rear servo.
• OK in 1 and 2, low in D3 and R: a leak in the front clutch area.
• Low in all positions: a clogged filter, a stuck regulator valve, a worn pump or low fluid.

Good pressure with no Reverse means a mechanical failure: burnt front clutch plates, a slipping band or strut, or the direct clutch. Low pressure in Reverse only brings the valve body back into it. Sonnax's vacuum test guide for the 46RE/47RE lists reverse slip, poor forward and reverse engagement and poor line pressure control as symptoms of a worn line pressure plug and sleeve. The manual's chart also lists valve body malfunction for no Reverse.

With the valve body off, air-check the circuits. Air on the front clutch apply passage should give a soft thump as the clutch applies. Air on the rear servo passage should extend the servo rod and tighten the band around the drum, and the rod should return when you release the air. A hiss with no movement means that circuit is leaking.

The Fix, by What You Found

• Cable or linkage: adjust it or replace the bushing, and confirm the lever is in the reverse detent.
• Rear band out of adjustment: adjust it to 72 in-lb and back it off 3 turns. If it will not hold after that, replace the band and check the drum OD and strut length.
• Rear servo: replace the piston with the correct year part and the reverse servo plug. Inspect the bore for wear.
• Front clutch or direct clutch burnt, or friction material in the pan: that is an overhaul. Use a full master rebuild kit, a new direct clutch spring, the servo piston and plug upgrades, and the piston retainer. Flush the cooler, and replace the converter if the unit made debris.
• Pressure low in Reverse with good parts: vacuum test the valve body and repair the line pressure plug and sleeve or the regulator valve, or replace the valve body.

Our 47RE slipping guide covers the full pressure test, and the 47RE fluid guide covers the hot level check.

Frequently Asked Questions

Why does my 47RE go forward but not in reverse?

Chrysler's chart for no Reverse with the D ranges OK lists the shift linkage, a sticking park sprag, the rear band, the valve body, the rear servo, a worn overdrive direct clutch and a burnt front clutch. The forward gears barely load the rear band and servo, so a band, servo or linkage problem usually shows up as no Reverse first. A road test in manual 1 and in third tells you which part to look at.

Can a band adjustment fix no reverse on a 47RE?

Yes, if the rear band is just out of adjustment. Drop the pan, torque the adjusting screw to 72 in-lb, back it off 3 turns and tighten the locknut to 25 ft-lb. If the band still will not hold, the band, strut, drum or rear servo is worn.

What is the most common cause of no reverse in a 47RE?

Sonnax and TransGo document three repeat failures. The rear servo piston binds in its bore, the aluminum reverse servo plug breaks at its spring seat, and the overdrive direct clutch spring fades and burns the direct clutch plates. A burnt front clutch is also common if third gear slips as well.

Will a 47RE with no reverse need a rebuild?

Not always. Linkage, band adjustment and some valve body problems can be fixed in the truck. A servo piston, a direct clutch or a burnt front clutch means pulling the transmission. If the pan has friction material in it, plan on an overhaul.

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Related 47RE guides

• 47RE Slipping: Causes and Fix
• 47RE Torque Converter Lockup Shudder Fix
• 47RE Common Problems and Fixes
• 47RE Valve Body Problems and Testing
• 47RE Harsh and Delayed Shifts
• 46RE No Reverse: Diagnosis and Fix
• 48RE No Reverse: Diagnosis and Fix