6R80 Navigator Slipping: Causes and Fix

A Navigator owner who says "it's slipping" can mean four different things, and only one of them is a burned clutch. On these trucks I have seen a launch in 5th, a sudden drop into 1st at speed, a converter that looks like it is slipping because the engine is surging, and a genuine worn-out E or C pack. They all get described the same way at the counter. The repair for each one is very different, and one of them is still sitting under a Ford extended-coverage program on some VINs.

This guide covers the 2009-2017 Lincoln Navigator with the 6R80: the 5.4L 3V trucks from 2009-2014 and the 3.5L EcoBoost trucks from 2015-2017. The 2018-up Navigator moved to the 10R80 and is not covered here. The clutch-by-gear logic is the same as the Expedition, so I will keep that part short and point you to our Expedition slipping guide for the full chart. Every source is listed at the bottom.

Recommended 6R80 parts

The parts that fix a Navigator 6R80 slip complaint: the AL3Z-7G276-D lead frame when the OSS signal is dropping out, a master rebuild kit when the clutches are burned, and a remanufactured 2015-2017 valve body when bore wear is bleeding off pressure. Secure checkout on site.

6R80 Lead Frame Connector with Valve Body Seal AL3Z-7G276-D

$275.99View part

6R80 Transmission Master Rebuild Kit, Ford F-150 Expedition Mustang

$383.99View part

6R80 Valve Body 2015-2017 - Remanufactured With Solenoids, Non Start/Stop

$525.00View part

Step one: is it a slip or a speed signal problem?

On a 2012-2013 Navigator, start with the electronics, not the clutches. Ford has three published documents on this platform that describe symptoms an owner will call slipping, and all three trace back to the molded lead frame on the main control (valve body) assembly.

Look at the code list on 16N02 and 19N01. P0731 is a gear 1 ratio code, the same code a burned clutch sets. The PCM calculates ratio from turbine shaft speed and output shaft speed. If the OSS signal drops out, the computed ratio goes wrong and the PCM flags a ratio error even though every clutch is holding. A shop that reads "P0731, incorrect gear ratio" and quotes an overhaul without checking the OSS signal can sell a Navigator owner a transmission it did not need.

A launch in 5th gear, the TSB 13-6-8 symptom, feels like the truck has no power and the engine is flaring. Most drivers call that a slip. The giveaway is in the TSB itself: the speedometer reads zero while the truck is moving. A slipping clutch never takes the speedometer with it.

How to separate them on the scan tool

• Graph OSS against an ABS wheel speed PID. If OSS drops to zero or spikes while the wheel speeds stay smooth, the fault is the sensor signal, which on this unit means the lead frame. A clutch slip leaves OSS tracking road speed and shows up as turbine speed running too high.
• Check the speedometer during the event. Zero speed or dashes on the odometer while moving points at OSS, per TSB 13-6-8.
• Read freeze frame on P0720, P0722 and P0731 together. An OSS code stored alongside a ratio code is a signal problem until proven otherwise. A ratio code alone, set at operating temperature under load, leans toward a real clutch slip.
• Run the VIN through Ford's program lookup. The 19N01 extended coverage ended on October 31, 2019 for trucks already past 10 years or 150,000 miles, and the supplement says vehicles over 150,000 miles are not covered. A lower-mileage 2012-2013 Navigator is still worth checking at a Lincoln dealer before anyone pays for the repair.

If you do the lead frame yourself, Ford's 16N02 procedure calls out 9 quarts of MERCON LV (XT-10-QLVC), filter BL3Z-7A098-A and pan gasket BL3Z-7A191-C as required, and torques the six long lead frame bolts to 53 lb-in (6 Nm) in sequence. Ford allows 2.2 hours of labor on a Navigator. 53 lb-in is inch-pounds. Do not reach for the foot-pound wrench on this job.

Step two: rule out the engine on a 2015-2017 EcoBoost

The 2015-2017 Navigator shares its 3.5L EcoBoost and 6R80 with the Expedition, and that combination has a documented false-slip case. Troy Hopp of Certified Transmission wrote up a 2015 Expedition 3.5L in Transmission Digest that came in with RPM surging and the scan tool showing converter clutch slip, with no codes. The shop replaced the transmission, updated the PCM, programmed the solenoid strategy and body ID, fixed a broken ground and swapped the converter. None of it helped.

What found it was a stationary stall test. With the truck standing still, the engine surged and the TCC slip PID swung exactly as it had on the highway, then P0234 (turbo overboost) set. Ford TSB 16-0013 addresses that turbocharger concern, and replacing the left turbo fixed the truck. TCC slip is engine rpm minus turbine rpm, so anything that makes the engine surge moves that number. On an EcoBoost Navigator with a "converter slip" complaint and no transmission codes, check boost, the charge air tubes and pending engine codes before the transmission comes out.

Step three: confirm a real clutch slip

If OSS is clean and the engine is steady, prove the slip with numbers. Graph turbine speed, output speed, commanded gear, engine rpm and transmission fluid temperature together. The 6R80 ratios are 4.17, 2.34, 1.52, 1.14, 0.87 and 0.69 for 1st through 6th. Multiply OSS by the commanded gear ratio to get the turbine speed you should see. Turbine speed running above that number with a steady gear command is a clutch slipping.

GEARS Magazine describes the 6R80 as having three driving clutches (A, B and E) and two brake clutches (C and D), with two applied in every gear. That makes the slip pattern a map:

• 2nd and 6th slip together: clutch C, the 2-6 clutch. Sonnax says the clutch C regulator valve oscillates and wears its bore, causing 2nd and 6th slip, ratio errors and eventually clutch C failure (kit 95740-40K).
• 4th, 5th and 6th slip, worst at highway load: clutch E, the 4-5-6 overdrive clutch. A Navigator that tows a camper in 6th lives on this pack.
• 3rd, 5th and Reverse: clutch B, the 3-5-R direct clutch.
• Slips in Forward and Reverse, delayed Reverse, TCC slip: line pressure. Sonnax ties these to spring-end wear in the pressure regulator valve bore (kit 95740-01K), which also exhausts converter feed and burns the converter clutch. Sonnax tests that bore with a vacuum check and lists 18 in-Hg as the minimum it should hold.

One Navigator-specific trap: the 2011 design change. GEARS documents that Ford added a one-way clutch to the rear planetary in 2011. On 2011-later units the D clutch only holds until about 3 mph, then the PCM releases it and the one-way clutch carries 1st. The D/E solenoid is normally high, applying D at about 50 mA and releasing it at about 850 mA. So on a 2011-2017 Navigator, a slip in 1st in Drive that goes away in manual 1st points at the one-way clutch, not a friction pack. On a 2009-2010 truck, D holds all of 1st and the same symptom points at D or its circuit. The parts are not interchangeable between the two designs.

Fluid: the cheap check that gets skipped

A Navigator that slips only hot, on a long grade or in a hard corner is often low. The 6R80 has no conventional dipstick; level is set at the fill plug with the engine running, the vehicle level and fluid temperature read on the scan tool. Our 6R80 fluid type and capacity guide walks through it.

Ford's Motorcraft fluid chart lists MERCON LV for the Navigator 6R80 3.5L EcoBoost and MERCON ULV only for the 10R80 that replaced it, and it warns against supplemental additives, treatments and cleaners. Use MERCON LV in every 2009-2017 Navigator. If the fluid is burnt and the pan has friction material, the fluid did not cause the slip and a fluid change will not cure it.

The repair, by what you found

1. Speedometer drops to zero, OSS codes, 5th-gear launch or sudden 1st: molded lead frame. Check the VIN for Ford coverage first on a 2012-2013.
2. Surge that repeats standing still, boost or engine codes: engine repair on the EcoBoost. Leave the transmission alone.
3. Low fluid, clean pan: set the level with MERCON LV at temperature, fix the leak, retest hot and loaded.
4. Slip with clean fluid that follows one circuit: valve body repair with the matching oversized valve, or a remanufactured valve body for the correct year.
5. Burnt fluid and a slip that follows one clutch: overhaul with all frictions and steels, air-check every piston, inspect the valve body bores, hot-flush the cooler.

After any valve body, solenoid or lead frame work, program the solenoid strategy and body ID codes into the PCM. Sonnax's Jim Dial explains that the PCM uses those codes to know each solenoid's banding and which clutch it controls, and that adaptation can often settle in three to five full up-and-down shift cycles once the right data is loaded. A good valve body with the wrong data still flares and still feels like a slip.

Need parts for this job?

Navigator 6R80 lead frames, remanufactured valve bodies by year, master rebuild kits and MERCON LV are on our 6R80 parts page, with checkout on site.

FAQ

Why does my Lincoln Navigator feel like the transmission is slipping?

On a 2009-2017 Navigator with the 6R80, the common causes are a failing molded lead frame that drops the output shaft speed signal, low or burnt MERCON LV, valve body bore wear, and burned clutches on high-mileage or towing trucks. On 2015-2017 EcoBoost models an engine or turbo surge can also look like converter slip. Graph output speed against ABS wheel speed before condemning the clutches.

Can a bad lead frame cause a slipping code on a Navigator?

Yes. Ford's 16N02 and 19N01 programs list P0731, a gear 1 ratio code, alongside P0720, P0722 and P1500 for the 2012-2013 Navigator lead frame failure. The PCM calculates gear ratio from turbine and output shaft speed, so a lost OSS signal sets a ratio code even when no clutch is slipping.

Why does my Navigator start out in 5th gear?

Ford TSB 13-6-8 covers 2012-2013 Navigators built on or before 4/8/2013 that launch in 5th gear, with the speedometer reading zero and the odometer showing dashes. The fix is a new molded lead frame, part AL3Z-7G276-A, and the bulletin says the shift solenoids do not need replacing.

Is the Navigator lead frame still covered by Ford?

Program 19N01 extended lead frame coverage on 2012-2013 Navigators to 10 years or 150,000 miles from the warranty start date. Coverage for trucks already past those limits ended October 31, 2019, and vehicles over 150,000 miles are excluded. Have a Lincoln dealer check the VIN for open programs.

What transmission fluid does a 2009-2017 Navigator use?

MERCON LV, Motorcraft XT-10-QLVC. Ford's fluid chart lists MERCON LV for the Navigator 6R80 and warns against additives and cleaners. Ford's lead frame program called for 9 quarts per job, and the level is set at the fill plug with the engine running at the specified temperature.

Related guides

• 6R80 Navigator Common Problems and Fixes
• 6R80 Expedition Slipping: Causes and Fix
• 6R80 Slipping: Causes and Fix
• 6R80 P0720 Fix
• 6R80 Valve Body Wear Fix