45RFE 3-4 Clutch Failure: Symptoms and Fix

Search "45RFE 3-4 clutch" and you will find plenty of people asking about it, but if you open a Chrysler service manual you will not find a clutch by that name. The 45RFE has no band and no GM-style "3-4 clutch." What people mean is the overdrive (OD) clutch: one of the three input clutches in the input clutch assembly, and the clutch that comes on during the 2-3 upshift and stays on through 4th. When it burns, the truck flares or slips in exactly the gears a GM tech would blame on a 3-4 pack, which is how the name stuck.

Below: why the OD clutch burns, how to prove it is the OD clutch and not the UD or 4C before teardown, and the clearances that decide whether the rebuild holds. Every spec is sourced at the bottom.

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Recommended 45RFE parts

Frictions, the input drum the OD clutch lives in, and a valve body for a worn switch valve bore. Secure checkout.

45RFE Transmission Master Rebuild Kit, Dodge Ram/Jeep

$287.99View part

45RFE Input Drum 1999-2007

$107.83View part

45RFE Valve Body 1999-2010

$417.99View part

Which Gears Use the OD Clutch

The RFE has three input clutches (underdrive, overdrive, reverse), three holding clutches (2C, 4C, low/reverse) and an overrunning clutch. Chrysler's clutch application chart for the 545RFE, which shares its gear train with the 45RFE, applies the OD clutch in these ranges (Chrysler Road Testing):

• 3rd gear (1.00:1): UD + OD
• 4th gear (0.75:1): OD + 4C
• 5th gear, 545RFE only (0.67:1): OD + 2C
• Limp-in in Drive: UD + OD (3rd gear)

Two things fall out of that chart. First, the OD clutch is the only element shared by 3rd and 4th (and 5th on a 545RFE). A slip that shows up in 3rd and 4th, but not in 1st or 2nd, points straight at the OD pack or its feed circuit. Second, and this catches people out: the RFE's failsafe default is 3rd gear. ATRA Technical Bulletin #990 notes that on an immediate shutdown the RFE series defaults to 3rd gear in Drive, with 2nd available if you pull the selector into 2 or L (ATRA TB #990). Because limp-in 3rd uses the OD clutch, a truck with a burned OD pack often has no good forward gear left once it drops into limp. Pull it into manual 2 and it usually drives, because 2nd is UD + 2C.

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Symptoms of a Failing 45RFE OD Clutch

The progression is predictable once you have seen a few of these:

• Flare on the 2-3 shift. RPM jumps for a moment before 3rd takes. This is the first time the OD clutch applies on a normal upshift, so it is often where the failure shows first.
• Slip or flare going into 4th, then a slip that comes and goes at highway speed in 4th, especially hot or under load.
• Gear ratio codes. P0733 (3rd gear ratio error) and P0734 (4th gear ratio error), together or one at a time. More on reading those below.
• Limp mode with almost no drive in D, while manual 2nd still pulls, for the reason covered above.
• Burnt-smelling, dark ATF+4 and friction material on the pan magnet.

One warning on timing: Chrysler notes that the gear ratio DTCs can take up to five minutes of problem identification before they light the MIL (Chrysler P0734 procedure). A short test drive with no light does not clear the OD clutch.

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Why the OD Clutch Burns

The burned frictions are what you see when the drum comes apart, but they are rarely the root cause. Chrysler's possible-causes list for P0734 reads like a map of the OD feed circuit: cut OD piston or accumulator seals, missing OD bleed orifices, a loose dribbler orifice in the reaction shaft support, a broken support seal ring, worn solenoid switch valve or plugs, and poor machining on the pump valve body face (Chrysler P0734 procedure). Sonnax narrows the usual culprits to three areas for the whole RFE family, 45RFE through 68RFE (Sonnax, RFE OD clutch failure):

1. Solenoid switch valve and plug bore wear

The solenoid switch valve bore has three plugs in it, and two of them move depending on gear. On the 1-2 shift the switch valve feeds the 2C circuit. On the 2-3 shift a bore plug strokes against the switch valve, and on the 3-4 shift it strokes the other way to feed the OD clutch circuit and hold the switch valve. Every shift cycles those plugs, and over time they wear the aluminum bore. A worn bore crossleaks OD apply oil, holding pressure drops, and the clutch slips and burns. Sonnax lists "OD clutch burned," bind-up and failsafe, plus codes P0841, P0868, P0871, P0988, P1775 and P1776, among the problems its switch valve plug kits fix.

2. The OD dribbler valve in the stator support

The dribbler is a controlled leak that precharges the OD circuit so the clutch applies on time. If it is restricted, the OD clutch applies late and drags on the way on. If it leaks, it holds too much pressure in the circuit and the OD clutch stays slightly applied when it should be released, so it drags in 1st and 2nd. Either way the pack overheats. Chrysler lists the same part as a "loose / missing dribbler orifice assembly in reaction shaft support."

3. Clutch pack clearance

Too tight and the pack fills too fast, applies too fast, and risks bind-up. Too loose and fill time gets longer, the clutch drags while it strokes, and it overheats. Sonnax also notes OE steels and frictions are thin and tolerate heat poorly.

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How to Diagnose It Before Teardown

Step 1: Fluid level and condition

Chrysler lists low fluid level first among the causes of both P0733 and P0734 (Chrysler P0733 procedure). Check it hot, at the dipstick temperature marks, with ATF+4 only. Chrysler's spec table lists Mopar ATF+4 as the recommended fluid for this unit (Chrysler 545RFE Specifications). Black, burnt fluid with friction material in the pan means a fluid change will not save it.

Step 2: Read the code pattern against the apply chart

This is the quickest way to point at a clutch without opening anything. Each gear ratio code tells you which pair of clutches failed to hold:

• P0733 (3rd) and P0734 (4th) together: the shared element is the OD clutch. That is your prime suspect, along with its feed: switch valve, dribbler, OD accumulator, reaction shaft support seal rings.
• P0733 alone: 3rd is UD + OD. Chrysler's P0733 list includes burned UD or OD clutch, cut UD or OD piston seal, and missing UD or OD bleed orifices. If 1st and 2nd (both UD) are also soft, lean toward the UD clutch.
• P0734 alone: 4th is OD + 4C. If 3rd is clean, look harder at the 4C clutch, the cut 4C tower seal and the 4C bleed orifice in the 2C/4C retainer, all on Chrysler's P0734 list.

Chrysler's procedure says to clear up any solenoid, line pressure, speed sensor or loss-of-prime DTCs first.

Step 3: Watch input and output RPM live

The ratio codes come from the two speed sensors. Chrysler states the input speed sensor reads 60 teeth on the input clutch hub and the output speed sensor reads 30 teeth on the park gear. With a scan tool showing Input RPM and Output RPM, the math is simple: in 3rd, input should equal output (1.00:1). In 4th, input should be 0.75 times output, so 2,000 rpm output means about 1,500 rpm input. When the OD clutch slips, input RPM climbs above that number under throttle while output stays steady. Also check the DTC event data: Chrysler's procedure looks for P1790 with Target Gear = 4th, or with both the 4C and OD clutches applying.

Step 4: Check the clutch volume index

The TCM learns a clutch volume index (CVI) for each clutch: basically how much oil it takes to stroke the piston. A worn OD pack has more clearance and takes more oil, so the OD CVI creeps up. Sonnax notes that some professional scan tools show individual clutch volume indexes, which helps find the problem. Watch whether it keeps climbing after a reset.

Step 5: Air check and vacuum test

With the pan and valve body off, Chrysler's procedure is to apply 30 psi of clean, dry air to each clutch apply passage. A working clutch gives a soft thump when it applies and releases when you take the air away (Chrysler Air Checking). If the OD port just hisses, the piston seal, the OD/reverse piston bleed orifice or the reaction shaft support seal rings are leaking. Air-test the dribbler separately: Sonnax says air should flow from the pump side to the drum side and not the other way. Then vacuum test the solenoid switch valve bore on the valve body. Sonnax recommends a vacuum test to decide whether the bore needs repair.

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The Fix: Clearances and Parts That Matter

A real repair covers the clutch pack and the circuit that burned it. Fit frictions and steels alone and you will see the truck again.

OD clutch clearance

Chrysler's spec table lists OD clutch pack clearance at 1.103-1.856 mm (0.043-0.073 in.), with UD at 0.84-1.54 mm (0.033-0.061 in.) and reverse at 0.81-1.24 mm (0.032-0.049 in.). Input shaft end play is 0.46-0.89 mm (0.018-0.035 in.) (Chrysler 545RFE Specifications). Check it, do not assume it.

Do not mix OD plates with UD or reverse plates

TransGo's 45RFE/545RFE instructions flag that on 45RFE, 545RFE, 65RFE and 2012-13 66RFE units, the OD frictions and steels are thicker than the UD and reverse plates: about 0.090 in. OD frictions and 0.087 in. OD steels, against 0.075 in. and 0.068 in. for UD and reverse. Build an OD pack out of the wrong plates and the clearance will be off before the drum ever goes back in (TransGo SK45RFE-A instructions).

Know which input drum you have

The UD/OD pressure plate changed in 2007. TransGo lists the 2007-up plate (p/n 68009902AC) with about 0.065 in. offset on the OD side and the 1999-06 plate (68009108AA) with about 0.021 in. offset. A 1999-06 unit may already have a 2007-up drum in it from a previous repair, so measure: top of drum to top of the 0.061 in. flat snap ring is 1.960 in. on a 2007-up drum and 1.907 in. on a 1999-06 drum. TransGo also replaces the factory tapered UD snap ring, which can break and pop out, with a 0.091-0.094 in. flat ring.

Fix the circuit, not just the pack

• Solenoid switch valve bore: if the vacuum test fails, ream and fit an oversized valve or plug kit, or replace the valve body. Sonnax's family writeup notes the original 45RFE-group valve has a 0.420 in. large spool and a later design (about 2010) went to 0.453 in., so measure the valve before you pick a kit (Sonnax, solenoid switch valve family).
• Dribbler and reaction shaft support: air test the dribbler, replace the support seal rings, and inspect the pump valve body face.
• Flush the cooler. Burned OD material in the cooler and lines will go straight into the new pack.

Torque values for reassembly

From Chrysler's spec table: valve body to case 12 N·m (105 in-lb), reaction shaft support bolts 12 N·m (105 in-lb), oil pump bolts 28 N·m (250 in-lb), accumulator cover screws 7 N·m (60 in-lb), solenoid module to transfer plate 6 N·m (50 in-lb), primary filter screw 4.5 N·m (40 in-lb), and oil pan bolts 12 N·m (105 in-lb).

Quick learn and drive learn afterward

New clutches and seals mean the old adaptive values are wrong. ATRA TB #990 says a quick learn resets more than 70 learn parameters and must be done after any repair to prevent premature failures during road testing. For the OD clutch specifically, it gives a drive-learn procedure for the first 2-3 shift: fluid above 80°F (27°C), select reverse for more than 2 seconds, then shift to Drive and accelerate at a steady 15-degree throttle through the 2-3 shift. Repeat until the first 2-3 OD CVI settles. If a shift is still rough after that, ATRA warns an internal problem may be present.

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Preventing a Repeat Failure

Heat is what kills the OD clutch once the hydraulics are right. ATRA's bulletin describes the RFE overheat strategy: above 240°F oil temperature or 244°F coolant, the TCM delays the 3-4 upshift to 41-48 mph and changes converter lockup behavior to protect the unit. If a truck keeps hitting that strategy when it tows, add cooling and use the right gear. Keep it on ATF+4, service it on the severe schedule if it tows, and test a fresh 2-3 flare right away. A slipping OD pack turns a valve body repair into a full rebuild quickly.

FAQ

What is the 3-4 clutch on a 45RFE?

The 45RFE does not have a clutch Chrysler calls the 3-4 clutch. The term usually refers to the overdrive (OD) clutch, one of the three input clutches, which applies with the underdrive clutch in 3rd gear and with the 4C clutch in 4th gear. On a 545RFE it also applies in 5th with the 2C clutch.

What codes does a burned 45RFE overdrive clutch set?

Most often P0733 (gear ratio error in 3rd) and P0734 (gear ratio error in 4th), because 3rd and 4th are the two gears that share the OD clutch. Chrysler notes these codes can take up to five minutes of problem identification before the check engine light comes on, so a short test drive may not show them.

Why does my 45RFE barely move in limp mode?

The RFE failsafe default in Drive is 3rd gear, which uses the underdrive and overdrive clutches. If the OD clutch is burned, limp-in 3rd slips badly. Manual 2nd uses the underdrive and 2C clutches instead, so moving the shifter to 2 usually gives you a gear that still pulls.

What is the 45RFE overdrive clutch clearance spec?

Chrysler's service specifications list OD clutch pack clearance at 1.103-1.856 mm, or 0.043-0.073 inch. The OD frictions and steels on 45RFE and 545RFE units are thicker than the underdrive and reverse plates, so building the pack with the wrong plates will throw the clearance off.

Will replacing the clutches alone fix 45RFE overdrive clutch failure?

Usually not for long. Worn solenoid switch valve bores, a restricted or leaking dribbler in the reaction shaft support, leaking seal rings, and incorrect clearance are what burn the OD pack in the first place. Vacuum test the valve body, air test the dribbler and clutch passages, set clearance to spec, and run a quick learn after the rebuild.

Related 45RFE guides

• 45RFE Won't Shift Into Overdrive
• 45RFE Slipping: Causes and Fix
• 45RFE Valve Body Problems and Testing
• 45RFE Limp Mode Causes
• 45RFE and 545RFE Gear Ratios and Specs