6R80 Expedition Slipping: Causes and Fix

An Expedition is a 6R80 working at the top of its rating. It is the heaviest vehicle Ford ever put this transmission in, a lot of them pull campers and boats, and the 2015-2017 trucks put twin-turbo torque into it at low rpm. When one of these comes in "slipping," the odds of a real clutch failure are higher than on a Mustang or a light-duty F-150. So are the odds that the shop down the road already replaced the wrong thing.

Two published Expedition cases show both sides of that: a 2014 5.4L that kept slipping in 5th after a rebuild because of a cracked piston, and a 2015 EcoBoost that got two transmissions for "TCC slip" when the fault was a turbocharger. The general logic for every 6R80 is in our 6R80 slipping guide. This one sticks to the 2009-2017 Expedition and Navigator. Every source is linked at the bottom.

Recommended 6R80 parts

The parts that fix a slipping Expedition 6R80: a master rebuild kit when the clutches are burned, a remanufactured valve body when bore wear is bleeding off apply pressure, and the MERCON LV it must be filled with. Secure checkout on site.

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

Motorcraft Mercon LV ATF 12-Quart Case for Ford 6R80

$181.99View part

Know which Expedition you have first

The 6R80 ran in the Expedition and Navigator from 2009 through 2017. The 2018 truck moved to the 10R80, so a 2018-up Expedition is a different transmission and a different fluid. Within the 6R80 years there are three groups, and they do not share all their parts:

GEARS Magazine documents the 2011 change. Ford added a one-way clutch to the rear planetary to smooth the 1-2 and 2-1 shifts, and that forced changes to the case, the C and D support, the rear planetary, the valve body, the lead frame, the harness and the PCM strategy for the D clutch. On the late design, the D/E solenoid is a normally-high unit: about 50 mA applies the D clutch and about 850 mA releases it. The PCM starts releasing D at roughly 3 mph and lets the one-way clutch hold 1st. Keep those numbers in mind when you read solenoid current PIDs on a 2011-2017 truck.

Prove the slip on the scan tool

Do not road test an Expedition for slipping without a scan tool on it. Graph turbine shaft speed (TSS), output shaft speed (OSS), 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, and 3.40 in Reverse. Multiply OSS by the ratio of the commanded gear and you have what TSS should read. At 1,800 rpm OSS in 5th, TSS should sit close to 1,570. If TSS runs above that while commanded gear holds steady, a clutch is slipping. If TSS tracks the ratio but engine rpm still flares, the slip is ahead of the turbine, which means the converter clutch or something that is not the transmission.

Two habits save time on these trucks:

• Log it loaded and hot. Many Expedition slips only show up on a grade with a trailer, with fluid temperature well above where it sits on a commute. A test drive around the block with 120°F fluid will pass a unit that slips at 220°F.
• Compare Drive to manual mode. On a 2011-2017 truck, a slip in 1st in Drive that disappears when you select 1st in manual mode (where the D clutch stays applied for engine braking) is the one-way clutch, not a friction pack.

Which clutch: the slip pattern tells you

GEARS describes the 6R80 as a Lepelletier geartrain with three driving clutches, A, B and E, and two brake clutches, C and D. Every gear uses two of them. A burned pack slips in every gear that uses it, so the pattern points at the clutch before the pan comes off.

The table is where to start, not where to stop. The ATSG case below is the best example I know of a slip that did not follow the textbook.

Case 1: 2014 Expedition 5.4L slipping in 5th

Wayne Colonna wrote this one up in Transmission Digest from an ATSG help line call. A 2014 Expedition 5.4L slipped in 5th and set a 5th gear ratio code. Only the E clutch (4-5-6 overdrive) plates showed a slight burn, and the heated drum showed no cracks. The shop rebuilt it, replaced the stator bushing and valve body, and it road tested fine.

It came back cycling 4-5, 5-4, 4-5 on the scan tool. Engine load, speed sensors and misfires checked out, and a second removal to inspect the B clutch (3-5-R) drum found nothing. On the third removal the E clutch (4-5-6) piston was cracked, a crack that had grown since the first teardown. ATSG noted this failure usually hits the shift into 4th, not 5th, which is why it hid so well. The shop sourced a matching piston from a ZF 6HP24 drum.

The lesson: burned E plates on an Expedition are a symptom. Air-check every piston with the plates installed and watch for slow bleed-off, and treat a slip that moves to another gear after a rebuild as a cause never found.

Case 2: 2015 Expedition EcoBoost "TCC slip" that was a turbo

Troy Hopp of Certified Transmission published this in Transmission Digest in May 2024. A 2015 Expedition 4WD with the 3.5L EcoBoost came in with RPM fluctuation and a whirring noise, right after a reman unit went in for converter shudder. No codes, clean full fluid, and the scan tool showed converter clutch slip during the RPM swing on uphill highway grades.

A second transmission, a PCM update, solenoid data, a ground repair and a different converter changed nothing. Then Hopp stall-tested it in the bay. Standing still, the whir appeared, the TCC slip PID surged just as it had on the highway, and P0234 (turbo overboost) set. Ford TSB 16-0013 covers that turbo concern, and a new left turbocharger fixed the truck.

TCC slip is a calculated number, engine rpm minus turbine rpm. If the engine surges, that number swings even when the converter clutch is holding. On an EcoBoost Expedition with no transmission codes, check pending engine codes and the charge air ducts, and try to reproduce the surge with the truck stationary. If it surges standing still, it is not a clutch.

Case 3: valve body wear that bleeds off apply pressure

Most high-mileage Expedition slips I see with clean fluid and no broken parts come from the valve body. The 6R80 controls every clutch with a regulator or control valve fed by a variable bleed solenoid, and those aluminum bores wear. Sonnax publishes three kits that line up with Expedition slip complaints:

• Clutch C regulator valve (Sonnax 95740-40K). Clutch C applies in 2nd and 6th. Sonnax says the valve oscillates and wears its bore, and the pressure loss causes 2nd and 6th slip, ratio codes, poor shift quality and eventually clutch C failure. A truck that tows in 6th on the highway wears this circuit hard.
• Clutch D1/E control valve (Sonnax 95740-08K). Bore wear here causes flare upshifts, downshift bind-ups, harsh 3-2 shifts, coastdown neutral and pressure control out-of-range codes. Note the fitment limit: Sonnax says it does not fit 2012-later 6R80 units that have an OE D1 valve with two equal-diameter spools, so check the valve before you order.
• Pressure regulator valve (Sonnax 95740-01K). Wear at the spring end of the bore lets line pressure and converter feed exhaust, which Sonnax ties to slips in Forward and Reverse, delayed Reverse, TCC slip and a burned converter clutch. Wear at the sleeve end does the opposite and raises line pressure enough to break drums and pistons. Sonnax lists different bore dimensions for the 2009-2014 and 2015-later units, so measure before mixing parts.

If you replace the valve body, or any solenoids, the PCM has to be told about them. Sonnax's Jim Dial explains that 6R80 variable bleed solenoids lose their calibration, or banding, over time, and the PCM needs the solenoid strategy and body ID codes to control them. With the right data loaded, he says the relearn can often be done in three to five shift cycles. Skip that step and a good valve body can still flare.

Fluid on an Expedition: check it right

An Expedition that slips only when hot, on a long grade or in a hard turn is often a quart or two low. There is no conventional dipstick on the 6R80. The level is checked at the fill plug with the vehicle level, the engine running and the fluid at the temperature called for in the service procedure, read on the scan tool. Our 6R80 fluid type and capacity guide covers the procedure.

The fluid is MERCON LV, Motorcraft XT-10-QLVC, in every 2009-2017 Expedition. Ford's Motorcraft fluid chart lists MERCON LV for the 6R80 Expedition and MERCON ULV only for the 2018-up 10R80, and it warns against supplemental additives, treatments and cleaners. For volume, Ford's own lead frame program 16N02 for the 2012 Expedition and Navigator called for 9 quarts of XT-10-QLVC per job, with filter BL3Z-7A098-A and pan gasket BL3Z-7A191-C as required. A pan drop alone gives up less than that because the converter and cooler stay full.

If the fluid smells burnt and the pan has friction material in it, a fluid change will not fix the slip. It only confirms a clutch has already been cooked.

The fix, by what you found

1. Surges standing still, boost or engine codes: engine repair on the EcoBoost. Leave the transmission alone.
2. Low fluid, clean pan: set the level with MERCON LV at temperature, find the leak, recheck the shifts.
3. Slip or flare with clean fluid, codes pointing at one circuit: valve body repair with the matching oversized valve, or a remanufactured valve body, then solenoid strategy and body ID programming and a relearn.
4. Burnt fluid and a slip that follows one clutch: overhaul with every friction and steel, air-check each piston for cracks, inspect the valve body, and hot-flush the cooler. On a towing Expedition I expect more than one pack to be damaged.
5. 2011-2017 slip in 1st that holds in manual 1st: one-way clutch.

After any internal repair, load the solenoid data, clear the adaptives and drive the relearn before the customer gets the keys. On a truck that tows, tell them to change the fluid on the severe-service schedule. Heat is what burns the E and C packs in these trucks.

Need parts for this job?

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

FAQ

Why is my Ford Expedition transmission slipping?

On a 2009-2017 Expedition with the 6R80, the usual causes are low or burnt MERCON LV, valve body bore wear that bleeds off clutch apply pressure, and burned clutches on high-mileage or towing trucks. On 2015-2017 EcoBoost models an engine or turbo surge can make the TCC slip reading swing and feel like a slip. Graph TSS, OSS and commanded gear before replacing anything.

Which clutch is slipping if my Expedition slips in 5th gear?

5th gear uses the B clutch and the E clutch. If 3rd and Reverse also slip, suspect B; if 4th and 6th slip too, suspect E. ATSG documented a 2014 Expedition that slipped in 5th because the E clutch (4-5-6) piston was cracked, so air-check the pistons, not just the plates.

Can a turbo problem make an EcoBoost Expedition feel like it is slipping?

Yes. Transmission Digest documented a 2015 Expedition 3.5L that had a transmission and a converter replaced for TCC slip and RPM surge. A stationary stall test reproduced the surge, P0234 set, and replacing the left turbocharger, the repair pointed to by Ford TSB 16-0013, fixed it. TCC slip is engine speed minus turbine speed, so an engine surge moves that number.

What fluid does a slipping 6R80 Expedition need?

MERCON LV, Motorcraft XT-10-QLVC, set at the fill plug at operating temperature. Ford warns against additives and cleaners in this transmission. If the old fluid is burnt and the pan has friction material in it, a fluid change will not fix the slip.

Will a fluid change fix a slipping Expedition transmission?

Only if the fluid was low or worn and no clutch has been damaged yet. Correct the level with MERCON LV and recheck the shifts loaded and hot. Burnt fluid with friction material in the pan means the unit needs an overhaul.

Related guides

• 6R80 Expedition Common Problems and Fixes
• 6R80 Slipping: Causes and Fix
• 6R80 F150 Slipping: Causes and Fix
• 6R80 Torque Converter Shudder
• 6R80 Valve Body Wear Fix