45RFE No Reverse: Diagnosis and Fix, From the Clutch Split to P0736

A 45RFE that pulls forward fine but just sits and revs in Reverse is one of the more straightforward failures on this unit, as long as you know how Chrysler builds Reverse. Two clutches make it. Neither one depends on the solenoid pack to apply. That single fact rules out half the parts counter before you pull a pan.

This guide covers how Reverse is built in the 45RFE and 545RFE, the symptom split that tells you which clutch let go, Chrysler's own P0736 test path, the valve body wear points that take Reverse away on a unit with good clutches, and the fix. The Chrysler, Sonnax and Transmission Digest references are listed at the bottom.

Recommended 45RFE parts

Burnt Reverse or L/R frictions mean a clutch module; a cracked L/R accumulator piston means the accumulator kit; a full teardown for cut piston seals means a master rebuild kit. Ships from the USA, secure checkout.

45RFE Clutch Module

$167.98View part

45RFE 545RFE 68RFE Billet Accumulator Piston Kit

$79.99View part

45RFE / 545RFE / 65RFE Master Rebuild Kit with 4WD Filter

$318.99View part

How Reverse Works on the 45RFE

Chrysler's clutch application chart for the 545RFE (the 45RFE uses the same geartrain) shows exactly two elements on in Reverse: the Reverse clutch and the Low/Reverse (L/R) clutch.

Two details in that chart drive the whole diagnosis:

• The Reverse and overdrive clutches share one piston. Chrysler's input clutch description says the overdrive clutch is applied against the overdrive/reverse piston, and so is the Reverse clutch. A cut OD/Reverse piston seal can hurt Reverse and 3rd, 4th and 5th at the same time.
• Reverse is hydraulic. Chrysler's operation description states that the hydraulic system alone, with no electronic assist, gives the transmission Park, Reverse, Neutral, 2nd and 3rd based only on shift lever position. That is what lets a truck in limp-in still back up. If a 45RFE has no Reverse, do not start by blaming the solenoid pack. You are looking at oil supply, the valve body, a clutch, or a broken part.

One more point matters for the scan tool. None of the five pressure switches sits on the Reverse clutch circuit. The controller only finds a Reverse problem by comparing input and output speed, and that comparison sets P0736, Gear Ratio Error in Reverse. A truck that nobody has tried to back up under load can have a dead Reverse and no codes at all.

Step 1: Split It Between the Two Clutches

Before anything comes apart, drive it and use the other gears to figure out which clutch is the problem. The shared piston and the shared L/R clutch make this quick.

• Check manual Low. The chart shows the L/R clutch on in 1-Low, alongside UD and the overrunning clutch. In Drive, 1st can ride on the overrunning clutch, so a burnt L/R pack often still pulls away in Drive. What it loses is engine braking coasting in manual 1. Drive fine, no engine braking in Low, and no Reverse points at the L/R clutch or its feed.
• Check 3rd, 4th and 5th. The OD clutch is on in all three. If Reverse is gone and the 3-4 or 4-5 shift flares, or the OD pressure switch is setting codes, suspect the OD/Reverse piston seals or the input clutch housing before either clutch pack.
• Reverse is the only problem. Manual Low holds, 3rd through 5th are firm, and only Reverse slips or is missing. That puts you on the Reverse clutch pack, the reverse hub and shaft, the reaction plate snap ring, or the reaction carrier. Those are covered in Step 5.

For a truck that slips in several ranges, not just Reverse, start with our 45RFE slipping guide.

Step 2: Fluid, Shifter and Line Pressure

1. Fluid level, hot. Low fluid is the first item on Chrysler's P0736 cause list. The 45RFE takes ATF+4; see our 45RFE fluid and capacity guide for the check procedure.
2. Shifter adjustment. Chrysler's gearshift cable check is simple. The engine should start in Park and Neutral and nowhere else. If it starts in only one of them, the adjustment is off. The Transmission Range Sensor reports Reverse as its own switch code, with "Temp 1" and "Temp 2" between-gear codes on either side of it. A lever that leaves the manual valve in a between position can give a weak or delayed Reverse. ATRA adds that a shift linkage out of adjustment can make the range sensor send transitional signals, which causes erratic shift complaints that do not set a code (ATRA Technical Bulletin 990).
3. Line pressure in Reverse. Chrysler's hydraulic pressure test on the 2007 545RFE is done hot at 1500 rpm. It lists in-gear Reverse pressure of 220 psi on the 4.7L and 250 psi on the 5.7L, against 120 psi in Neutral. The N-R garage shift targets the same 220 and 250 psi. You can read line pressure on the scan tool or tee a gauge in with adapter 8259, and the two readings should agree within 10 psi. Chrysler notes these units run closed-loop pump pressure, so readings can move around, but they should always follow line pressure.

Good Reverse line pressure with no Reverse means the oil is reaching the valve body and getting lost somewhere past it. Low line pressure in every range is a pump, filter or regulator problem, and our 545RFE pressure testing guide covers that.

Step 3: Chrysler's P0736 Path

P0736 sets when the input-to-output speed ratio in Reverse does not match the Reverse gear ratio. Chrysler notes it can take up to five minutes of problem identification before the MIL comes on. Follow the procedure in order. It is built to stop you from tearing into a unit for a code that something else set.

1. Clear the related codes first. Chrysler says to handle any solenoid, line pressure, speed sensor or loss-of-prime code before P0736, and to run the P0944 Loss of Prime test first if it is stored. Record the transmission DTC event data before you clear anything.
2. Run the clutch test. The scan tool clutch test checks whether input speed stays at zero with the element applied. Chrysler's caution is not to overheat the transmission while doing it. If the test passes and the event data shows zero input speed when the code set, look for an intermittent fault before condemning hard parts.
3. Air check the circuits. With the pan and valve body off, Chrysler says to apply 30 psi of clean, dry air to each clutch port. A working clutch gives a soft thump on apply and releases when the air is removed. One Chrysler note saves a lot of confusion: the Reverse circuit has a bleed orifice that connects to the OD clutch cavity, so a small amount of air leaking into the OD circuit while you air Reverse is normal.
4. If the clutch test fails in Reverse, check the reaction carrier. Chrysler's next question is whether the reaction carrier is turning faster than the drive shell. If it is not, the call is to replace the reaction carrier, because the reverse sun gear weld to the reaction carrier has broken. If it is, go to the reverse carrier hub, and if that is good, disassemble and inspect the input clutch assembly.

Chrysler's full P0736 cause list reads like a map of the circuit:

• Low fluid level
• Cut L/R tower seal on the main valve body
• Cut L/R clutch piston seals, or a broken or missing L/R clutch bleed orifice in the L/R clutch retainer
• Cut L/R accumulator piston seal, or a cracked L/R accumulator piston, in the main valve body
• Cut OD/Reverse piston seals, or a broken or missing OD/Reverse bleed orifice in the OD/Reverse piston
• Broken reverse carrier hub weld
• Broken reverse sun gear weld to the reaction carrier

If clutch debris turns up, Chrysler says to pull the unit and inspect both the Reverse and L/R clutches, plus the pump and main regulator valve for damage or sticking in the bore.

Step 4: The Valve Body Wear Points

A 45RFE can lose Reverse with good clutches if the oil never gets to them. Three places matter.

L/R switch valve bore

Sonnax describes the RFE low/reverse switch valve as a one-way valve for the L/R clutch in Reverse and Drive. The valve is heavily side-loaded because its diameter is close to its length, and the bore wears. Once it does, oil leaks past and exhausts through the manual valve. Apply pressure drops and you get a burnt L/R clutch, delayed Reverse or no Reverse. Sonnax's fix for the 45RFE, 545RFE and 68RFE is the drop-in checkball sleeve kit 92835-41K, or the oversized 92835-45K for bores with heavy wear. On vacuum test, Sonnax treats 18 in-Hg as passing and anything lower as worn. You have to shuttle the valve by hand to each port to get a real reading.

L/R accumulator and tower seal

Both appear on Chrysler's P0736 list, and they get skipped because they live on the main valve body instead of in the clutch pack. Sonnax's RFE vacuum test guide lists delayed engagement and L/R clutch failure as symptoms in this area, with accumulator piston and sleeve kits that are specific to the 45RFE and 545RFE. Check the L/R accumulator piston for cracks and its seal for cuts, and replace the tower seal any time the valve body is off.

Checkballs and test plugs after a valve body job

Sonnax's RFE checkball article says the #3 checkball routes Reverse oil through an orifice to soften garage shifts. Leave it out and Reverse engagement gets firm, not lost, so a harsh Reverse after a valve body job points here. A missing #1 ball causes a different problem: the L/R clutch applies off the manual valve and binds 2nd. For a unit with no movement at all after a valve body swap, Transmission Digest documented an RFE with zero line pressure because the clutch pressure test plugs came in a separate bag in the box and were never installed. Check the plugs before you condemn anything else. Our 45RFE valve body testing guide covers the other bores.

Step 5: Inside the Input Clutch Assembly

If the valve body tests good and air goes to the Reverse port without clutch action, the unit comes out. Chrysler's final step in the P0736 test lists what to inspect in the input clutch assembly:

• The Reverse clutch reaction plate snap ring. If it is out of its groove, the pack has nothing to clamp against.
• The OD and Reverse clutch seals and discs. Because they share a piston, a torn seal usually shows up as trouble in both clutches.
• The bleed orifice in the OD/Reverse piston. Chrysler lists a broken or missing orifice here as a cause of P0736, so inspect it every time the piston is out.
• The reverse hub and shaft. Look for stripped splines or a broken weld. The reverse carrier hub weld and the reverse sun gear weld are separate failures, and both are on Chrysler's list.

A useful ID tip from the Chrysler assembly pages: the Reverse and UD clutches share common separator plates, and the UD frictions are tan with a cross-hatched groove pattern. Stack the packs in the right places and get the select snap ring right on the way back together.

Quick Diagnostic Order

1. Pull codes and event data. Fix solenoid, line pressure, speed sensor and loss-of-prime codes first.
2. Check fluid level hot, confirm ATF+4, and look in the pan for friction material.
3. Confirm the engine starts only in Park and Neutral, and that the TRS reads Reverse with the lever in R.
4. Split the failure using manual Low (L/R clutch) and 3rd through 5th (OD/Reverse piston).
5. Gauge line pressure in Reverse at 1500 rpm hot: about 220 psi on a 4.7L and 250 psi on a 5.7L 545RFE.
6. Pan and valve body off: air check at 30 psi, vacuum test the L/R switch valve bore to 18 in-Hg, and inspect the L/R accumulator and tower seal.
7. No clutch action on air with a good valve body means the unit comes out. Check the reaction carrier weld, the reverse hub, the snap ring and the OD/Reverse piston seals.

The Fix, by Root Cause

• Worn L/R switch valve bore, clutches still good: sleeve the bore with 92835-41K or 92835-45K, or install a correct-year replacement valve body.
• Cracked L/R accumulator or a cut tower seal: replace the accumulator piston and seals on the main valve body.
• Burnt Reverse or L/R frictions, or leaking pistons: overhaul with new frictions, steels and all piston seals. Inspect the input clutch retainer's sealing surfaces, because new seals will not hold on a scored drum.
• Broken reverse sun gear weld or reverse carrier hub: replace the reaction carrier or hub. No friction kit fixes a broken weld.

After any valve body or internal repair, run the Quick Learn so the controller relearns clutch volumes. Otherwise the new parts can shift harshly or flare and set codes. ATRA notes that quick learn resets more than 70 learn parameters to their preset values, and that the vehicle still has to be driven afterward to fine-tune them (ATRA Technical Bulletin 990). The drive-learn steps are in our 45RFE harsh shift guide.

Related guides

• 45RFE Delayed Engagement: Causes and Fix
• 45RFE Slipping: Causes and Fix
• 45RFE / 545RFE Valve Body Problems: Symptoms and Testing
• 45RFE Limp Mode Causes and Fix
• 545RFE Line Pressure Testing: Specs and Procedure
• 68RFE No Reverse: Diagnosis and Fix

FAQ

Why does my 45RFE have Drive but no Reverse?

Reverse on a 45RFE needs two clutches, the Reverse clutch and the Low/Reverse clutch. In Drive, 1st gear can be carried by the overrunning clutch, so a failed L/R clutch or a worn L/R switch valve bore can leave Drive working while Reverse is gone. Chrysler's P0736 cause list also includes cut OD/Reverse piston seals, a cracked L/R accumulator piston and broken welds on the reverse carrier hub or reverse sun gear.

Can a bad solenoid pack cause no Reverse on a 45RFE?

It is rarely the cause. Chrysler states that the hydraulic system alone gives the 45RFE and 545RFE Park, Reverse, Neutral, 2nd and 3rd based on shift lever position, which is why a truck in limp-in can still back up. Check fluid, shifter adjustment, line pressure, the valve body and the clutches before buying a solenoid pack for a Reverse complaint.

Will a 45RFE go into Reverse in limp mode?

Yes. Limp-in removes power from the solenoids, but Reverse is still available through the manual valve and line pressure. If a 45RFE has no Reverse even in limp-in, the problem is hydraulic or mechanical, not electronic.

What should 45RFE line pressure be in Reverse?

Chrysler's hydraulic pressure test for the 2007 545RFE, done hot at 1500 rpm, lists 220 psi in Reverse on the 4.7L and 250 psi on the 5.7L, with 120 psi in Neutral. The scan tool line pressure reading should agree with a gauge within 10 psi.

What causes P0736 on a 45RFE?

P0736 is Gear Ratio Error in Reverse. Chrysler lists low fluid, a cut L/R tower seal, cut L/R clutch piston seals or a missing L/R bleed orifice, a cut seal or cracked L/R accumulator piston, cut OD/Reverse piston seals or a missing OD/Reverse bleed orifice, a broken reverse carrier hub weld, and a broken reverse sun gear weld to the reaction carrier. Fix solenoid, line pressure, speed sensor and loss-of-prime codes first.