5R55S Lincoln LS Fluid Change: Type, Capacity and Cost

The Lincoln LS is one of the easiest cars to get a fluid service wrong on. There is no dipstick, no filler tube, and the level is set from underneath with the engine running. A 5R55S that is a quart or two low will slip and flare long before it sets a code. This is the whole job: what fluid, how much, when, how to drain it, how to set the level, and what it should cost.

One note on years first. Sonnax's Bob Warnke points out that the 2000-2002 LS used the 5R55N, and the 5R55S replaced it in the Lincolns and Thunderbirds for 2003 [5]. This guide is written for the 5R55S cars, 2003-2006. Parts like the solenoid base plate and filter do not interchange with the N.

Recommended 5R55S parts

The Motorcraft MERCON V Ford specifies for the LS, a full case so you can drain the converter and still set the level, plus the rest of our 5R55S parts. Secure checkout on our site.

Motorcraft Mercon V ATF - Case of 12 Quarts (XT5QMC)

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All 5R55S parts: solenoids, shift kits, rebuild kits

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What Fluid Goes in a Lincoln LS 5R55S

Ford's 2005 Lincoln LS owner guide is blunt about it: use only MERCON V, the fluid type is marked on the transmission pan and extension housing, and a non-approved fluid may cause internal damage and void the warranty [1]. The lubricant table lists Motorcraft MERCON V ATF, part XT-5-QM [1]. The guide also warns that MERCON and MERCON V are not interchangeable and should not be mixed [1]. That warning matters on the LS more than most cars, because the power steering on the same car takes plain MERCON (XT-2-QDX) [1]. Two red fluids, two specs, one engine bay. Do not let the power steering jug end up in the transmission.

Motorcraft's current product page lists MERCON V as XT-5-QMC (quart, case of 12), XT-5-5Q3M (5 quart) and XT-5-DMC (55 gallon), and it says not to use it where MERCON SP, MERCON LV, MERCON ULV, CVT chain fluid or Type F is called for [6]. Read that in reverse for the LS: none of those newer Ford fluids belong in a 5R55S. "Newer" is not "better" here.

Why the fluid itself was part of the 5R55 story

This is the part most fluid guides skip. Warnke at Sonnax explains that the 5R55 family had a solenoid problem that traced back to the fluid: the factory fill used an early MERCON V, prior to May 2005, that degraded the solenoids [5]. Ford released an interim additive package, 4L2Z-19B546-AB (fluid XL-11, bulletin FSA 04B22), for customer cars and new inventory, and the final resolution was a revised MERCON V, XT-5-QM in a black quart container [5]. Sonnax adds that if a service leaves trace amounts of the questionable fluid in the unit, the service life of the next solenoid can be reduced [5].

On a 2003-2005 LS that has never had a real fluid service, that is a strong argument for draining the converter and not just dropping the pan. It is also why I do not run additives in these units. Ford's owner guide says not to use supplemental additives, treatments or cleaning agents [1], and the scheduled maintenance guide says Ford recommends against additive products unless Ford specifically calls for one in an application [2]. XL-11 was that one exception, and it was an interim fix that the revised fluid replaced.

How Much Fluid It Takes

Ford's service information puts a note right under its capacity chart: capacities are approximate, and the correct level is determined by the fluid level check procedure, not by the amount added [3]. That is the rule on every 5R55. Measure what comes out so you know roughly what to expect, then let the check plug tell you when it is full. The owner guide makes the same point in its footnote: fluid level should be checked by a qualified technician [1].

When to Change It

Ford's 2006 Scheduled Maintenance Guide puts the LS on the "Normal Schedule Cars & Minivans," along with the Thunderbird and Mustang [2]. On that schedule, the automatic transmission fluid change comes up at 150,000 miles [2]. The "Special Operating Conditions" page moves it to every 30,000 miles if the car is used for towing or a car-top carrier, extensive idling or long low-speed driving, dusty or unpaved roads, or off-road operation [2]. Ford's service information for the same transmission adds hot weather above 90°F with heavy loads or hilly terrain to the 30,000-mile list [3].

My take: every LS on the road today is fifteen to twenty years old, and many live in summer heat and stop-and-go traffic. I treat almost every one as severe service and recommend 30,000 to 50,000 miles. That is a judgment call, not a Ford spec.

Ford's owner guide gives one more trigger that matters more than mileage: check the fluid level if the transmission slips, shifts slowly, or there is any sign of a leak [1]. On a car with no dipstick, a slow leak can run the unit low for months before anyone notices.

Tools You Need

• A scan tool that reads the TFT PID. Both Ford's procedure and ATRA's bulletin set the level by fluid temperature [3] [4].
• A 3/16-inch Allen key for the small center level plug, and a wrench to hold the larger drain plug around it [3].
• Fill adapter 307-437, which threads into the center of the drain plug [3] [4].
• A suction gun (Ford lists 303-D104) or a fluid transporter to push fluid in from below [3] [4].
• An inch-pound torque wrench. Most of this job is in inch-pounds.
• A new filter for the LS, a pan gasket if yours is damaged, and a new converter drain plug if the converter has one.

On the filter: buy it by application, not by "5R55S." The LS, Thunderbird and Mustang pan filter is cataloged separately from the Explorer and Mountaineer filter in the aftermarket, so an Explorer kit is the wrong part even though both transmissions say 5R55S on the tag. Compare the old and new filter side by side before the new one goes in. Sonnax gives the same advice for the solenoid body filter [5].

Drain and Refill, Step by Step

This follows Ford's draining and refilling procedure for the 5R55W/S, written for the Explorer chassis but covering the same transmission family [3]. The pan and plug layout on the LS is the same design: no dipstick, a large drain plug with a small level plug in its center [4].

1. Drain the pan. Raise and support the car, remove the drain plug and let it drain. Then remove the 16 pan bolts, the pan and the gasket [3].
2. Pull the filter. Remove the bolts and discard the filter. Clean and inspect the pan and magnet [3]. Fine gray paste on the magnet is normal; bronze flakes or steel slivers are not.
3. Drain the converter if you can. Ford's procedure removes the converter housing access plug and the converter drain plug. A new converter drain plug must be used to prevent leakage, torqued to 89 lb-in (10 Nm), and then the access plug goes back in [3]. Not every converter in the field still has a drain plug, so look before you plan your fluid order around it.
4. Install the new filter. Make sure the filter seals are seated on the filter and lubricated with ATF. Ford's caution: lubricate the seals with clean ATF or they may be damaged [3]. A rolled pickup seal lets the pump pull air.
5. Reinstall the pan. Ford calls the pan gasket reusable if it cleans up without damage [3]. Start all 16 bolts loosely, then tighten in a crisscross sequence to 97 lb-in (11 Nm). The drain plug is 19 lb-ft (26 Nm) [3].
6. Pump in the first fill. Hold the large plug, remove the center plug with the 3/16-inch Allen key, install the 307-437 adapter and pump in MERCON V until it runs back out [3]. If you use pressurized fill equipment, Ford says to reduce the pressure to one psi. Higher pressure can push fluid out of the vent, and it then looks like a leak from the torque converter area [3].

Setting the Level Correctly

This is where most LS fluid jobs go wrong. The first fill only gets the pan full. The level has to be set with the engine running and the fluid in a narrow temperature window. ATRA Technical Bulletin 746 lays out the procedure for the 5R55N, 5R55S and 5R55W [4]:

1. Connect the scan tool and monitor PID TFT. The fluid needs to end the procedure between 80-120°F (27-49°C) [4]. Ford's service information gives 81-120°F [3].
2. Start the engine. Idle should be about 650 rpm [4]. Move the selector slowly through each range, then put it in Park [3].
3. With the engine running, get the car as level as you can on the hoist [4]. A car tipped nose-up or nose-down will read wrong at the plug.
4. Hold the large drain plug with a wrench and remove the small center plug with the 3/16-inch Allen key [4]. Wait about one minute. When fluid comes out as a thin stream or a drip, it is at the correct level [3].
5. If nothing comes out, install 307-437 and add fluid. Ford's procedure adds about one pint with the suction gun, waits a minute, then continues in 1/2-pint increments until fluid starts to drain from the plug [3]. ATRA's version uses a fluid transporter at no more than 30 psi of shop air, one pint at a time [4].
6. Let the excess drain, confirm TFT is still in the window, and reinstall the center plug. The bulletin's illustration gives 10 Nm (89 lb-in) [4].
7. Move the selector slowly through each range, stopping in each so the transmission engages, and check for leaks [3] [4].

Two bench habits that are mine, not Ford's. First, if I drained the converter, I set the level, drive the car ten minutes, and set it again at temperature. Second, I never set the level on a cold car and call it done. A cold LS "full" at the plug is low once it warms up, and it will tell you so on the first hard 2-3 shift.

When the Level Will Not Hold

If fluid keeps coming out of the vent, or the level reads full and the car still slips, do not just keep adding fluid. Sonnax notes that excessive valve body bore wear can aerate the fluid, and the suspended bubbles create an excessive fluid level that vents from the case or causes erratic pressure [5]. Overfilling, or fill pressure above Ford's one psi, can also put fluid out the vent and fake a converter-area leak [3]. Foamy, pink, bubbly fluid at the plug is a valve body or suction-side problem, not a fluid problem. Our LS slipping guide covers how to chase it.

Should You Flush It?

Ford's own position is reasonable: the maintenance guide says flushing is a viable way to change fluid for many systems, as long as it is done with the same fluid required to finish the service or a Ford-approved flushing chemical [2]. So a MERCON V exchange is fine on a healthy LS. What I avoid is any machine that adds a cleaner or "conditioner"; Ford's owner guide prohibits cleaning agents in this transmission [1]. Backflushing the cooler and lines after a failure, which Ford's service information requires [3], is a different job.

What a Lincoln LS Fluid Change Costs

Ford does not publish a price, so this section is my experience, not a spec. Parts are a filter and gasket, a converter drain plug if fitted, and MERCON V. A pan-only service uses roughly half a case; a service with the converter drained can use most of a case. Labor runs about an hour to an hour and a half on a lift. In my experience an independent shop usually lands somewhere around $200 to $400 for a pan, filter and converter-drain service on an LS with Motorcraft fluid, and a dealer more. A "$99 transmission service" that does not include a scan tool and the 307-437 adapter is not setting the level on this car.

FAQ

What transmission fluid does a Lincoln LS take?

The 2003-2006 Lincoln LS with the 5R55S takes Motorcraft MERCON V only, part XT-5-QM in Ford's owner guide (sold today as XT-5-QMC by the quart). Ford warns that MERCON and MERCON V are not interchangeable, and Motorcraft says MERCON V should not be used where MERCON LV, ULV or SP is specified, so none of those belong in an LS either.

How many quarts of transmission fluid does a Lincoln LS hold?

Ford lists 11.2 L (11.9 qt) as the approximate dry capacity, including the cooler and tubes. A pan and filter service takes back far less, and Ford says the correct level is set by the check procedure at the pan plug, not by the amount added. Buy a full case of 12 if you are draining the converter.

Does the Lincoln LS have a transmission dipstick?

No. Ford's owner guide states the 5R55S does not have a transmission fluid dipstick. The level is checked at a small center plug in the pan drain plug with the engine idling in Park, the car level, and fluid temperature between 80-120 degrees F on the TFT PID.

How often should Lincoln LS transmission fluid be changed?

Ford's normal car schedule, which lists the LS, changes the transmission fluid at 150,000 miles. Towing, extensive idling or low-speed driving, dusty roads and off-road use move it to every 30,000 miles. On a car this old, a 30,000 to 50,000 mile interval is a sensible choice.

How much does a Lincoln LS transmission fluid change cost?

Ford does not publish a price. An independent shop typically charges around $200 to $400 for a pan, filter and converter-drain service with Motorcraft MERCON V, and a dealer more. The job needs a scan tool that reads TFT and the 307-437 fill adapter, so a cheap service without them is not setting the level correctly.