47RE Shudder - Causes and Fix

47RE Shudder - Causes and Fix

47RE Shudder - Causes and Fix

A 47RE shudder almost always shows up the same way: the Cummins is cruising at light throttle somewhere around 45 to 55 mph, the converter clutch tries to lock, and the whole truck vibrates like it is driving over rumble strips. Give it more throttle and it smooths out. Let off and it comes back. Owners describe it as a warped converter, a driveline problem or a bad u-joint, and sometimes it is. But on a 47RE the shudder is usually the torque converter clutch slipping and grabbing because it is not getting the apply pressure or the friction it needs. This article walks through how to tell the difference, what wears out inside the valve body to cause it, and which parts fix it.

Parts for your 47RE

47RE Master Rebuild Kit - Frictions & Steels, Gaskets & Seals, Filter, Shift Kit, Servo, Solenoids, Bushings (7-Piece) — $346.99

See all 47RE rebuild kits

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Confirm it is TCC shudder

The 47RE locks the converter in 3rd and 4th, so a true converter shudder only happens in those gears with the TCC applied. The quickest test is to make it come and go on command:

  1. Drive at the speed where it shudders with the OD switch on and hold light throttle.
  2. Tap the brake pedal lightly. On the 47RE, the brake switch drops lockup. If the shudder stops instantly when the pedal is touched and returns a few seconds later, it is TCC shudder.
  3. Turn OD off and repeat in 3rd. If it still shudders only when the converter locks, the diagnosis is the same.
  4. If the vibration is there in all gears, at any throttle, and does not change with lockup, look at u-joints, the pinion bearing, tire balance and the driveshaft instead.

Gears Magazine documented a 47RE that stalled coming to a stop and dragged as it warmed up; the shop looped the cooler lines, unplugged the transmission connector, inspected the valve body for flatness, blocked the converter clutch valves to separate hydraulic from mechanical faults, and air-checked the front clutch, eventually finding a warped stator support cross-leaking front clutch oil into the converter passages. The sequence is a good model for any 47RE converter complaint: electrical first, then valve body, then cross-leaks, then the pump.

What causes 47RE shudder

1. Wrong or worn-out fluid

The 47RE was built for ATF+4, and the friction characteristics of ATF+4 are what let the converter clutch apply smoothly. Monster Transmission's 47RE/48RE guide lists contaminated fluid, incorrect TV calibration and low line pressure as the primary causes of converter shudder and lock problems and specifies ATF+4 only. Old fluid that has lost its friction modifier, or a truck that has been filled with a generic multi-vehicle fluid, will shudder. This is the cheapest cause to rule out, so it is the first fix to try.

2. Worn lockup boost valve in the valve body

This is the big one. Sonnax states that Chrysler 42-46-47-48RH/RE transmissions have a lockup boost valve that is prone to wear, and when it wears it causes a loss of converter and lubrication flow that results in TCC slip and an overheated converter. Their symptom list for the worn valve reads like a 47RE shudder complaint: TCC slip under load, no line rise during TCC apply in 4th, overheated converter, TCC cycling and no lockup. The cause is excess boost valve bore wear that reduces oil to the switch valve, leaving it in a partial stroke position that restricts the converter and lube circuits. The correction is an oversized lockup boost valve kit (Sonnax 22771-19K) installed with the matching reamer.

3. Worn 4-spool switch valve

Sonnax's valve body layout for these units tags the 4-spool switch valve with the exact symptoms of lockup shudder, overheated converter, low cooler flow and soft TCC apply. The switch valve is what routes oil to apply and release the converter clutch; a worn one gives a soft, partial apply that lets the clutch slip and chatter.

4. Low line pressure and a lazy TV setting

The 47RE still uses a throttle valve cable, and a mis-set TV cable lowers line pressure at the throttle position where lockup happens. Monster's guide notes that a small movement of about 1/8 inch changes shift points by roughly 75 rpm, and lists verifying pressure against spec and setting the TV correctly as part of the shudder fix. Owners on Cummins Forum who report shudder when the converter locks in 3rd and OD frequently find the answer is more line pressure.

5. Worn converter clutch lining

If the valve body has been leaking apply pressure for years, the clutch inside the converter has been slipping for years. At that point the lining is glazed and the shudder will not fully go away with fluid or a valve kit. The converter needs to be replaced, and if the old fluid was dark and smelled burnt, the clutch material has been circulating through the whole unit.

6. Solenoid or electrical faults

The overdrive/TCC solenoid on the 47RE is a common failure, and cheap replacements are a known problem. Cummins Forum threads on 47RE lockup problems repeatedly trace no-lockup and erratic lockup to bad or low-quality OD solenoids, and Transmission Digest points out that the 46RE/47RE transmission control relay is only powered when the engine is running, so solenoid circuits must be tested with the engine on, not just the key. A solenoid that is electrically intermittent produces an on-off-on lockup that feels exactly like shudder.

The fix

Work from cheapest to most expensive:

  1. Fluid and filter service with ATF+4. Drop the pan, change the filter, adjust the bands, refill with ATF+4 and drive it for a few hundred miles. If the shudder was fluid-related it will fade.
  2. Set the TV cable and check line pressure. Tap a gauge into the line pressure port and confirm pressure rises with throttle. A 47RE that will not build line rise will not hold its converter clutch.
  3. Test the OD/TCC solenoid and the relay circuit with the engine running. Replace with a quality unit if it is out of spec.
  4. Fix the valve body. This is where most persistent 47RE shudder lives. A 47RE shift kit recalibrates the springs and valves and raises apply pressure; TransGo's kit for the 48RE sibling specifically claims to correct TCC slip or shudder and reduce converter drain-back through higher line pressure and a line-to-converter feed. If the lockup boost valve bore is visibly worn, add the oversized boost valve kit, and on a high-mileage valve body consider a full Sonnax Sure Cure kit, which lists lockup shudder, soft TCC apply and overheated converter among the concerns it addresses.
  5. Replace the converter if the shudder survives all of the above, or if the fluid came out burnt. Options are in the torque converters collection.
47RE Shift Kit 1990-Up valve body recalibration kit
47RE Shift Kit 1990-Up - recalibrated valve body springs, valves and separator plate components that restore TCC apply pressure.

Replace while you are in there

  • OD/TCC solenoid and governor pressure solenoid and sensor - the 47RE Shift Solenoid Kit 2000-Up with Sensor covers the 2000-up electronic governor units; more options are in the solenoids collection
  • Boost valve spring retainer - the OE retainer cracks and lets the boost valve and spring fall out of position, leaking 4th gear and TCC oil
  • Filter, pan gasket and a full ATF+4 fill
  • Band adjustment on both bands
  • Cooler flush - a slipping converter clutch sends debris to the cooler, and low cooler flow feeds the overheat that ruins the next converter

If the teardown goes deeper than the valve body, the 47RE Master Transmission Rebuild Kit 1998-2002 with Filter covers the clutches, seals and filter for a full rebuild.

Cost and effort

A fluid service and TV adjustment is a driveway job with a few quarts of ATF+4 and a filter. A shift kit is a pan-off, valve-body-out job that takes an afternoon and does not require pulling the transmission. Oversized valve kits need the Sonnax reamer and a drill fixture, which is shop territory for most owners. A converter replacement means the transmission comes out, so it is the most expensive step and the one to save for last unless the fluid is already burnt. For background on the family, see 47RE vs 48RE and our general guide to TCC shudder.

Frequently Asked Questions

Will changing the fluid fix a 47RE shudder?

Sometimes. If the truck has old fluid or the wrong fluid, a filter change and a refill with ATF+4 can eliminate a light shudder. If the shudder is from a worn lockup boost valve or a glazed converter clutch, fluid alone will not fix it.

How do I know if it is the converter or the valve body?

If the shudder improves after a shift kit or boost valve repair but does not fully go away, or if the fluid was burnt, the converter clutch lining is worn and the converter needs to be replaced. Worn valves cause the problem; a glazed converter is the result.

Can I drive with a 47RE shudder?

A slipping converter clutch makes heat, and heat kills the 47RE. Turning OD off keeps the converter unlocked at highway speed, which stops the shudder but raises temperatures. Treat it as a repair to schedule soon, not something to live with.

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