47RE 3-4 Clutch Failure: Symptoms and Fix

People search for the "47RE 3-4 clutch" because GM units like the 4L60E have a clutch with that name. The 47RE does not. On the Chrysler RE family the 3-4 shift does not happen in the main case at all. It happens in the overdrive unit bolted to the back of it, and two clutches trade jobs: the overdrive clutch applies and the overdrive direct clutch releases. When a 1995-2002 Ram 2500 or 3500 with the 5.9L Cummins or 8.0L V10 flares on the 3-4, slips in fourth with a trailer on, or loses fourth altogether, one of those two packs or the pressure feeding them is nearly always the cause.

This guide covers how the overdrive unit makes fourth gear, how to separate an electrical no-4th from a mechanical slip, the plate counts and snap ring traps you meet on the bench, and the parts that keep it from happening again. The rebuild details come from the ATSG 46RE/47RE/48RE technical manual. Hydraulic detail comes from Sonnax and ATRA's GEARS magazine. Sources are listed at the end.

Recommended 47RE parts for an overdrive clutch job

Frictions, steels and seals for the overdrive pack, the compressor for the 830 lb direct spring, and the harness that carries the overdrive solenoid. Secure checkout.

47RE Transmission Master Rebuild Kit with Filter

$254.99View part

47RE Overdrive Clutch Spring Compressor Tool T-1302

$76.99View part

47RE Internal Wiring Harness

$92.99View part

How the 47RE Makes Fourth Gear

Per the ATSG manual, first through third come from the main case: the front (direct) clutch, rear (forward) clutch, kickdown band, low/reverse band and low roller clutch working a TorqueFlite-style geartrain. Fourth comes from the rear section, which holds an overdrive clutch, an OD/direct clutch, an overrun roller clutch and a single planetary gearset. ATSG lists the OD/direct clutch as an input driving component and the overdrive clutch as a holding component. Fourth is 0.69:1.

The overdrive unit has two states:

• First through third (1:1 through the overdrive). The overdrive direct clutch locks the overdrive sun gear to the planetary so the whole unit turns as one. Nothing hydraulic holds it on. A single large spring clamps it, and ATSG warns that spring force is approximately 830 pounds. The overrun roller clutch carries drive torque. On coast, the roller clutch freewheels, so the spring-applied direct clutch is what gives you engine braking.
• Fourth (0.69:1). The PCM energizes the overdrive solenoid, oil strokes the 3-4 shift valve, and the overdrive piston applies the overdrive clutch. That holds the sun gear to the overdrive case. The same piston travel pushes the clutch hub against the 830 lb spring, which releases the direct clutch.

That is why a "3-4 clutch" failure on this unit can be either pack. The overdrive clutch has to beat the spring and then hold engine torque multiplied by the planetary. The direct clutch has to hold first-through-third torque and coast loads on spring force alone. A fault in either one shows up around the 3-4 shift.

The control side is simple. GEARS (Dave Skora, October 2006) puts it plainly: these are hydraulically controlled transmissions for the first three gears, with governor pressure moving the shift valves. ATSG confirms that the 3-4 upshift is not influenced by governor pressure at all. It is controlled strictly by the overdrive solenoid, and the solenoid is used for nothing but the 3-4 shift.

Symptoms, Sorted by Which Pack Is Failing

Overdrive clutch (slips in fourth)

• Flare on the 3-4 shift. Rpm drops, then climbs back before fourth takes.
• Slip in fourth under load, especially towing up a grade or at highway speed with the converter locked. Rpm creeps up with no throttle change.
• Delayed or soft 3-4 that gets worse as the fluid warms.
• Black, burnt-smelling fluid and friction material in the pan with first through third still shifting fine.

Overdrive direct clutch (slips everywhere but fourth)

• Slipping or no reverse.
• Reduced or no engine braking in manual 2 or manual 1.
• Bind-up or a harsh 4-3 if the pack is warped or the hub is dragging. Full no-4th tree: 47RE won't shift into overdrive.

TransGo, which makes the replacement spring, describes the direct clutch side well: these units often come in with faded overdrive direct clutch springs and burnt overdrive direct plates. A faded spring means less clamping force, which leads to exactly the reverse slip and lost coast braking above.

Rule Out the Electrical Side First

A truck that simply will not go into fourth, with no rpm drop at all, is usually not a burnt clutch. Burnt overdrive frictions still give you a partial shift and a flare. A dead circuit gives you nothing. Check these before you pull anything:

1. Overdrive switch. Per ATSG, the switch has to be in the normal (ON) position to energize the OD solenoid and allow a 3-4 upshift. Tow/Haul or O/D OFF mode resets to ON every key cycle. Make sure the lamp is not lit.
2. Fluid temperature. ATSG notes that above 127C (260F) the PCM forces a 4-3 downshift and applies the converter clutch on the third-gear schedule. Chrysler's 1998 Ram service manual (pp. 21-212/213) fills in the rest of the logic: no overdrive or converter lockup below 50F, no 3-4 upshift above 250F, and fourth restored once the fluid cools to 230F. A truck that "drops out of overdrive" while towing on a hot day may be protecting itself. See our 47RE overheating guide.
3. Solenoid and harness. The overdrive and TCC solenoids are built into the internal wiring harness and case connector assembly. ATSG gives 25-40 ohms for each solenoid. Measure at the case connector, then at the PCM, to catch a chafed external harness. If the overdrive solenoid reads open or shorted, replace the harness assembly or the solenoid for your year.
4. Codes. The ATSG code list includes 3-4 shift solenoid circuit and "no rpm drop at 3-4 shift" faults. The first is electrical. The second is the PCM telling you the shift was commanded but the ratio did not change, which points back to hydraulics or the overdrive clutch. Chrysler's "No 3-4 Upshift" diagnosis chart in the 1998 Ram service manual (pp. 21-230/231) lists 15 possible causes, from the overdrive switch and solenoid through the valve body and the overdrive clutch itself, so work it in order rather than jumping to the pack.

Prove It: Scan Tool, Pressure and Air

Watch the ratio change

With a scan tool, log engine rpm (or turbine speed if your tool shows it) against output speed through a light-throttle 3-4 shift. Fourth is 0.69:1, so with the converter unlocked, rpm should fall about 30 percent and stay there. If rpm drops and then climbs back, or drifts up under load at a fixed throttle, the overdrive clutch is slipping. If you see no change at all while the PCM says fourth is commanded, go back to the electrical checks.

Check line pressure in fourth

The overdrive clutch is fed straight off line pressure, so low line pressure will make a healthy pack slip. Sonnax's article on 48RE hydraulics explains that in fourth (or in third with TCC on), the 46/47RE pressure regulator drops one of its reducing areas so line pressure rises roughly 10-15 psi, specifically to give the converter clutch and overdrive clutch more clamping force.

GEARS points out a shortcut: above about 40 mph the PCM turns the governor solenoid off, so the governor circuit sees full line pressure and the governor pressure sensor is really reading line pressure while you drive in fourth. Watch "governor actual" on the scan tool in fourth, confirm it with a gauge on the governor tap, and compare it to the same reading in third. If it does not rise in fourth, or reads well below the rest of the range, fix the pressure problem before you condemn the clutch. GEARS adds that more than 105 psi in third or fourth at wide-open throttle points to excessive line pressure or a bad transducer.

Air check the overdrive circuits

With the pan and valve body off, the ATSG case passage chart identifies two overdrive feeds for the 46RE and 47RE: overdrive clutch pre-fill and overdrive clutch apply. Use regulated, low-pressure air with the passage clean. A good overdrive clutch applies with a solid thump and holds air with only a light leak at the sealing rings. A hiss you can hear from the extension housing, or air that blows straight through, means a damaged piston seal, a cracked or worn piston retainer, or a leaking support at the case. If the pack applies cleanly but the truck still slips in fourth, the frictions themselves are done. If you have a gauge set, Chrysler's hydraulic pressure Test Six in the same service manual checks the overdrive clutch circuit directly and gives you a number instead of a sound.

On the Bench: What You Will Find and What Goes Wrong

Overdrive clutch pack

ATSG lists two overdrive clutch stack-ups. Gasoline units use 5 frictions and 5 steels with a flat (no-step) backing plate. Diesel units use 6 frictions and 6 steels with a stepped backing plate installed step-down. Do not mix the backing plates. Count the plates as you take them out, and check the build tag before you order a friction kit. Per ATSG, the part number and build date are on the bar code label on the left side of the case and are etched into the pan rail.

The snap ring trap

The gasoline overdrive pack uses three different snap rings in three locations: a wire-type retaining ring, a waved ring and a flat ring, with the waved and flat rings sharing one groove at the backing plate. ATSG calls installing these in the wrong place "a very common mis-assembly error." The diesel pack has no waved ring. Get it wrong and you change the overdrive clutch clearance and apply feel. Lay the rings out in order as they come off.

Overdrive direct clutch and the 830 lb spring

To get at the direct clutch you have to compress the spring. ATSG specifies compressor tool 6227-1 or an equivalent and a shop press with at least 5 to 6 inches of travel and an adjustable bed, with the output shaft flange (not the ball bearing) sitting on press plates. Release it slowly. That spring stores enough energy to hurt someone, and a screwdriver is not a compressor.

Plate counts per ATSG: the 46RE ran 8 frictions and 7 steels (double-sided frictions) in the overdrive direct pack. The 47RE ran 10 double-sided frictions and 9 steels. The 2003 48RE moved to a single-sided stack of 12 inside-spline and 11 outside-spline plates, then went back to 10 and 9 double-sided in 2004. ATSG notes the 10/9 double-sided stack can replace the single-sided stack because the height difference is minimal.

Replace the spring at every overdrive rebuild. TransGo's TFOD-SP high-temp spring is a direct replacement for OEM 4461027 and fits all RE-family overdrive units from 1988 on. A new pack behind a faded spring will burn again.

Piston retainer and lube

Look hard at the overdrive piston retainer, the six-bolt support the overdrive piston rides in. Sonnax's 22754N-01K retainer kit exists because the OE retainer wears excess clearance against the intermediate shaft, which cuts lube flow to the geartrain. Many OE supports also do not seal well against the case, which lets lube oil escape and drags down pump volume. The symptoms Sonnax lists are loss of lube to the planetaries and reverse drum, retainer and planet failure. A leaking retainer bleeds overdrive apply oil too. If the bushing bore is scored or the case face shows wear, replace the retainer instead of just resealing it.

Selectives on reassembly

ATSG calls out two selectives you must set before the overdrive goes back on the case: the intermediate shaft spacer and the number 10 thrust plate. They are measured with Chrysler tool 6312 through the sun gear, with the output shaft unloaded. The spline alignment tool (C-6227-2 or a modified intermediate shaft) has to stay in the overdrive planetary and roller clutch cam from assembly until installation. ATSG calls this step mandatory, because otherwise the overdrive will not go onto the transmission without coming apart again.

Do not confuse it with the front (direct) clutch

Chrysler also calls the main-case front clutch the "direct" clutch, and its clearance spec is not the overdrive spec. Sonnax's input shaft kit instructions give OE front clutch clearance as .070-.129 in. for the 47RE 4-clutch drum and .098-.161 in. for the 48RE 5-clutch drum. Use the overdrive specs for the overdrive and the drum specs for the drum.

The Fix, and Keeping It Fixed

1. Overdrive clutch burnt: new overdrive frictions and steels (5/5 gas, 6/6 diesel), new piston seals, correct snap ring order, retainer inspected or replaced, selectives set. Find out why it burned: line pressure, a leaking retainer, overheating or the wrong valve body.
2. Direct clutch slipping: new 10/9 pack and a new high-temp spring. Inspect the clutch hub and sun gear splines.
3. Both burnt, with debris in the pan: this is a full overhaul. Clean the cooler and flush the lines, or the debris goes straight back into the new parts. See 47RE rebuild cost for what drives the bill.

Prevention on these trucks comes down to heat, pressure and fluid:

• Fluid. ATSG states the 46RE, 47RE and 48RE require ATF+4. Do not top off with a generic multi-vehicle fluid.
• Heat. Run a real cooler and a temperature gauge on a tow rig, and use Tow/Haul or O/D OFF on long grades so the overdrive is not hunting.
• Pressure. Keep the valve body correct for the unit. Sonnax warns that the 48RE uses a different pressure regulator curve and TCC feed, and a 46/47RE valve body on a 48RE can run fine briefly and then come back with a burned converter clutch or overdrive clutch.

Frequently Asked Questions

Which clutch does the 3-4 shift on a 47RE?

The overdrive clutch in the rear overdrive unit. On the 3-4 shift the overdrive piston applies the overdrive clutch and, through the clutch hub, compresses the roughly 830 lb spring that holds the overdrive direct clutch on in first through third. The main-box front and rear clutches do not change state on the 3-4 shift.

Why does my 47RE slip only in 4th gear?

Slip that shows up only in fourth, or as a flare on the 3-4 shift, points at the overdrive clutch pack or the pressure feeding it. Burnt overdrive frictions, a leaking overdrive piston seal or retainer, low line pressure, or a mis-assembled backing plate snap ring are the usual causes once the electrical side has been cleared.

What does a weak overdrive direct clutch spring cause?

The overdrive direct clutch is applied by spring force alone. TransGo notes that once the spring fades, clamping force drops, leading to slipping or no reverse, reduced or no coast braking in manual 2nd or 1st, and burned overdrive direct clutch plates. Replace the spring at every overdrive rebuild.

Can I fix 47RE overdrive slip without pulling the transmission?

Only if the cause is electrical or hydraulic control: the overdrive solenoid, the internal harness, the overdrive switch, low fluid, or line pressure. If the overdrive frictions are burnt, the overdrive unit has to come apart, which on a 47RE means pulling the transmission and setting the intermediate shaft selective spacer on reassembly.