45RFE Won't Shift Into Overdrive: Causes, Diagnosis and Fix

"It won't go into overdrive" is one of the most common 45RFE complaints, and it covers two very different trucks. One is a truck where the controller never asks for 4th. The other is a truck that asks for 4th, tries, and fails. The first is usually a switch, a sensor, a temperature schedule or a shifter adjustment. The second is the 4C or OD clutch circuit.

This guide covers the 45RFE (Ram 1500, Dakota, Durango, Grand Cherokee, Liberty) and the 545RFE, where the same logic applies to 4th and 5th. It follows Chrysler's 45RFE/545RFE diagnostic procedures, ATRA's bulletin on RFE shift strategies and Sonnax's TASC Force notes. Sources are at the bottom.

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What 4th Gear Actually Needs

The 45RFE has no band and no dedicated overdrive unit. Fourth is built by applying the OD clutch and the 4C clutch together. Chrysler's pressure switch table (from the P0988 procedure) shows which switches should be closed in each gear, and it is the fastest way to see what the transmission thinks it is doing:

*Per Chrysler, L/R reads closed in 1st only when output speed is below 100 rpm in Drive and Manual 2, and always in Manual 1.

The 3-4 shift is a clutch swap: UD releases while 4C applies, and OD stays on. A truck that pulls 3rd fine has already proven the OD clutch holds, at least at light load, so 4C is the new element on the 3-4. When the controller commands 4th and the ratio does not follow, 4C and its circuit are the first suspects, not the OD clutch. On a 545RFE that will take 4th but not 5th, the new element is 2C instead.

Step One: Is the Controller Even Asking for 4th?

Drive it with a scan tool on. Watch commanded gear, actual gear (or input and output rpm), transmission temperature and lever position, and sort the truck into one of two piles:

• Never commands 4th: the controller is choosing not to. Something it reads (a switch, the temperature, the lever position, a stored fault) is telling it 4th is not allowed. Keep reading this section.
• Commands 4th, ratio does not follow, or it shifts and falls back: a hydraulic or mechanical problem in the 4C or OD circuit. Skip to the clutch sections below.

The Tow/Haul overdrive-off switch

Check the obvious one first. Chrysler describes the Tow/Haul overdrive OFF switch as a momentary contact that toggles overdrive. Overdrive is allowed at key-on; one press enters overdrive-off mode and lights the lamp, a second press restores normal overdrive. The mode resets to overdrive-on every time the ignition is cycled. The manual is explicit that the switch must be in its normal on position to allow a 3-4 upshift.

So if the lamp is on, the truck is doing what it was told. If the lamp is off after a key cycle and it still will not take 4th, the switch is not your problem, unless it is intermittent. Watch the overdrive status on the scan tool while you drive; it should not change unless someone presses the button. Location varies by model: on the Commander it sits in the lower center instrument panel switch bank, while other RFE applications put it on the shift lever.

Limp-in: stuck in 3rd is not "no overdrive"

If the truck will not take 2nd or 4th, it is not an overdrive problem. It is limp-in. ATRA Technical Bulletin 990 lays out the RFE shutdown modes: in an immediate or orderly shutdown the controller de-energizes the transmission control relay and the RFE defaults to 3rd gear in Drive, with 2nd available only if the lever is moved to 2 or L. A logical shutdown uses only 1st and 3rd in Drive at a preset line pressure. Either way, pull the codes and diagnose the fault that caused the shutdown. Our 45RFE solenoid guide covers the electrical side.

Temperature: the shift schedules

The RFE controller runs different shift schedules by fluid temperature, and two of them hold off 4th on purpose. ATRA Bulletin 990 lists them:

A truck that will not take 4th for the first few miles on a winter morning may be running exactly as designed. A truck towing hard that stays in 3rd until 45 mph is in the overheat schedule, and Chrysler's P0218 (High Temperature Operation Activated) is an informational code that sets once the overheat schedule is triggered at 260 F. Listed causes include a slipping converter clutch and long idling in gear. Fix the heat, not the shift. Our 545RFE overheating guide covers coolers and TCC checks.

The temperature sensor itself can cause the complaint. On these units it is a thermistor built into the transmission range sensor on the solenoid/TRS assembly. If it fails, Chrysler says the controller substitutes a calculated temperature from ambient temperature, coolant temperature and in-gear run time. P0711 flags a reading that never reaches operating temperature; the procedure's warm-up times run from about 10 minutes starting at 60 F to 25 minutes at -20 F. Transmission temperature lagging far behind coolant after a real drive means a cold-schedule truck: fix the sensor circuit or solenoid/TRS assembly, not the clutches.

Shift lever position: the "Temp" codes

This one catches experienced techs. Chrysler's range sensor reports lever position as five switch states, decoded into seven gear positions plus five "between gear" positions, Temp 1 through Temp 5. Temp 3 sits between Neutral and Drive, and Temp 4 sits between Drive and Manual 2. A lever or cable that parks the sensor in a transitional code instead of Drive changes what the controller will do.

ATRA's bulletin puts it plainly: a shift linkage out of adjustment that feeds transitional range signals to the module causes erratic shift concerns that will not set a code. With the lever in OD, the scan tool must read OD, not a temporary T3 or T4 value. Chrysler adds P1715 (Restricted Manual Valve in T3 Range), which sets after three failed attempts to engage 1st with the lever in the Temp 3 zone, and notes it can be set simply by the driver pushing forward on the lever while in OD. The quick cable check from the service information: the engine must start in both Park and Neutral.

Watch the lever position PID while wiggling the shifter in Drive. If it flickers into a Temp code, fix the cable first.

Step Two: It Commands 4th and Will Not Hold It

Now the problem is inside the case. Start with the codes, because on this unit the controller tests every clutch circuit it is not using.

Electrical: OD and 4C solenoid circuits

P0760 (OD solenoid circuit) and P0770 (4C solenoid circuit) come from Chrysler's inductive-spike continuity test, run at power-up and every 10 seconds, and immediately after any ratio or pressure switch error. The P0760 procedure calls it "strictly an electrical fault" that cannot be caused by an internal transmission failure other than an open in the solenoid/TRS assembly, and warns: if the solenoid/TRS assembly needs replacing, do not replace the valve body. Check harness and connector first, then the assembly.

The 4C circuit: P0987, P0988 and P2704

The pressure switch tests are the best clues on a no-4th truck.

• P0987 (4C Hydraulic Pressure Test). After a shift into a forward gear with the engine above 1000 rpm, the controller briefly turns on pressure to clutch circuits that are not in use and checks that each pressure switch closes. If the 4C switch fails to close twice, the code sets, the MIL comes on and the transmission goes to the orderly shutdown routine. The procedure first checks that line pressure holds steady at 85 to 95 psi and that the line pressure sensor connection is good.
• P0988 (4C Pressure Switch Rationality). The 4C switch read open or closed at the wrong time for the gear. Listed causes include excessive fluid leakage in the 4C clutch circuit, a cut or damaged number 5 check ball, low line pressure, and the solenoid/TRS assembly. If every switch reads open with line pressure under 40 psi, look at fluid level, the primary filter seal and the main regulator valve instead.
• P2704 (Inadequate Element Volume 4C). The controller learns a clutch volume index (CVI), the oil volume needed to stroke each piston. The 4C CVI is updated on the 3-4 upshift at 10 to 54 degrees throttle with fluid at least 110 F, and the code sets when it falls below 5. A near-zero volume means something mechanical is wrong. Chrysler's cause list leads with a broken 4C return spring or dislodged snap ring and broken 4C accumulator springs.

That P2704 cause list lines up with a known RFE-family failure. Sonnax's TASC Force reports the 4C return spring retaining ring in the 45/545/65/66/68RFE can come unseated and pop off, and Sonnax released a 4C retaining ring and shim kit (72978-01K) that fixes the retention and adds clearance options for 4C. If a 45RFE suddenly lost 4th, check that ring when the unit is apart.

The ratio code: P0734

If 4th applies but slips, you get P0734 (Gear Ratio Error in 4th). Chrysler's procedure has you record the event data and check whether input rpm reads zero (a speed sensor problem, go to P0715) and whether line pressure was more than 10 psi below desired (filter, regulator valve, then clutches). The cause list covers both clutches that make 4th: cut OD or 4C piston and accumulator seals, missing OD or 4C bleed orifices, a cut 4C tower seal, a broken reaction shaft support seal ring, a worn solenoid switch valve, and burned OD or 4C clutches.

Use 3rd to split them. If 3rd (UD plus OD) holds under full throttle and 4th slips, lean toward 4C. If 3rd also flares at wide open throttle, the OD clutch is failing and 4th is just where it shows first. The OD clutch failure pattern and Sonnax's checklist for it (solenoid switch valve bore wear, the stator dribbler, clutch clearance) are in our 45RFE slipping guide.

Air check before you condemn anything

With the pan and valve body off, Chrysler's air check uses clean, dry air at 30 psi; a working clutch applies with a soft thump. Per the P0734 procedure, the OD and 4C circuits both have small bleed orifices and the OD bleed connects to the reverse cavity, so a little leakage there is normal, not a cut seal.

A Diagnostic Order That Works

1. Check the O/D OFF lamp and cycle the key. Pull codes; fix anything that caused a shutdown first.
2. Compare transmission temperature to coolant. Below 36 F or above 240 F, a delayed 3-4 is by design.
3. Confirm lever position reads OD, not T3 or T4, and that the engine starts in Park and Neutral.
4. Road test: no 4th command means inputs; a command with no ratio change means the 4C or OD circuit.
5. Check line pressure against desired and the 4C CVI, then pan off, debris check and air check.

After the Repair

Run the Quick Learn with a scan tool after replacing the solenoid/TRS assembly or doing any internal repair. ATRA notes it resets more than 70 learned parameters to base values, and the truck still has to be driven to fine-tune them. If a shift is still rough after the clutch volumes stabilize, ATRA warns there may be an internal problem, and to confirm the controller has the latest software.

Related guides

• 45RFE Slipping: Causes and Fix
• 45RFE Shift Solenoid Symptoms, Testing and Replacement
• Chrysler 45RFE and 545RFE Transmission Problems and Fixes
• 45RFE vs 545RFE Differences
• 545RFE Overheating Prevention
• 68RFE Won't Shift Into Overdrive

FAQ

Why won't my 45RFE shift into overdrive?

Either the controller is not asking for 4th or the 4th gear clutches cannot hold it. Common no-command causes are the Tow/Haul overdrive off mode, a cold or overheat shift schedule, a shifter reading a between-gear Temp position, and limp-in. If it commands 4th and fails, look at the 4C circuit codes P0987, P0988 and P2704 and the 4th gear ratio code P0734.

Does cold weather stop a 45RFE from shifting into overdrive?

Yes, by design. Per ATRA, below -16 F the RFE uses only 1st and 3rd in Drive, and between -12 F and 36 F the 3-4 upshift is delayed. A failed temperature sensor that reads cold can hold the truck on the cold schedule after it is warm.

Can a misadjusted shifter stop a 45RFE from shifting into 4th?

It can. If the cable leaves the range sensor in a transitional Temp 3 or Temp 4 position, shifting goes erratic and often no code sets. The scan tool must read OD with the lever in OD, and the engine should start in both Park and Neutral.