Ford 6R140: Repairing the elusive intermittent neutral condition

Ford 6R140: Repairing the elusive intermittent neutral condition

The 6R140 has been in large Ford trucks since 2011 and is now considered a common unit in most shops. Our discussion today concerns the elusive intermittent neutral condition. At one particular time, this complaint was so common at one particular California utility company with a fleet of trucks that there seemed to be no solution in sight.

For this company, the vehicle was a 2016 Ford F550 6.7L with PTO and a bucket for line work. The transmission was repaired about 9,000 miles prior to its return to the shop with a complaint of intermittent neutral Forward or Reverse. The original build included a valve body with solenoids, pump and programming along with standard items such as clutches, converter and seals.

In discussion, we decided that since this truck had no other drivability complaints and was repaired recently, it was unlikely to have problems with common failure items that are known to cause no-movement issues, such as cracks or breakage of weld in the 4-5-6 overdrive clutch housing (Figure 1A) or cracks in the forward clutch drum that contains the 1-2-3-4 and 3-5-R clutches. Take notice of sealing rings, as damage to these rings can go hand in hand with a damaged 4-5-6 clutch housing (Figure 1B).

Figure-1A-1B-Overdrive-Clutch-Housing-1400
Figures 1A and 1B.

While performing multiple test drives, we were unable to reproduce the complaint. Additionally, both line pressure test and ATF level seemed normal; the line pressure spec. was 90–260 PSI.

We decided that the shop owner should drive the truck home overnight for a cold startup test the next morning. However, about an hour after closing shop, he called to say that he experienced the problem again. Luckily, the line pressure gauge was still on it. He said that it went to 0 PSI when he began driving up his inclined driveway. He had a neutral condition until he rolled back down the driveway. That was the revelation; the clue we were looking for.

The next morning, we were convinced the vehicle was low on ATF, so we added another quart. We then drove to an inclined parking easement to see if we could reproduce the neutral condition and quickly found that we could. We returned to the shop since something didn’t seem right. We thought and checked the level again, and it was within normal range. After discussion, we decided to pull the pan and check level of the ATF according to the stick with the pan off, hypothesizing that an incorrect dipstick was in the truck.

With the pan off, the ATF level seemed normal per the dipstick (right at pan rail to case level, like most units) so we decided to have a look at the filter. As we pulled the filter bolt, the filter dropped into the drain pan like a box of rocks. How could that be? The filter seal around the neck had no resistance whatsoever. We decided to replace the seal with a more robust O-ring we found. After reinstalling and filling with the same ATF, we again the checked the level and it showed to be right at the edge of being overfilled while cold.

Back to the same parking lot incline. This time, we were unable to recreate the neutral condition again. The ATF — level after a thorough warm up to the required 196–216°F — settled into the upper level of the correct normal operating range with one additional pint of ATF.

Over time, the shop repaired multiple trucks with this same scenario and now only occasionally hears this complaint. Figure 2A contains an image of the actual filter seal from the truck, and we never found any other problems with these filters. Keep in mind that this issue is not unique to the 6R140; it can occur in any Ford transmission that utilizes a round filter intake with the seal on the filter snout. Figure 2B shows a proper filter seal for this application.

Figure-2A-BFilter-Seal-1400
Figures 2A and 2B.

Fill procedure

This transmission fluid fill procedure mimics the OE procedure and will apply to most 6- through 10-speed Ford units. With a scanner, read the transmission temperature. It must be at operating temperature 196–216°F for a final validity check. If transmission fluid is needed, add transmission fluid in increments of 0.24L (0.5 pints) until the correct level is achieved and only after two to three extended road tests while at normal operating temperature. After you are satisfied with the level, go to a location where there is at least a 20–30° incline you can drive up (front end of vehicle first) to verify there is no possibility of a neutral condition. 

Warning: Do not overfill 6- through 10-speed Ford transmissions under any circumstance, as it may cause an overheated ATF condition.

Ford 6R140 uses Mercon LV ATF:

  • If only the transmission fluid drain plug or pan was removed, add 7.8L (8.2 qt.) of ATF.
  • If the valve body was removed, add 9.7L (10.2 qt.) of transmission fluid.
  • If the transmission was removed and disassembled, add 15.3L (16.2 qt.) of transmission fluid.

 Be advised of the dipstick ATF level instructions for late 6R140 transmissions (Figure 3).

Read more columns from the TASC Force Tips series here.

Jim Mobley is a Sonnax technical communications specialist. He is a member of the Sonnax TASC Force (Technical Automotive Specialties Committee), a group of industry technical specialists, transmission rebuilders and Sonnax technicians.

Thank you to Andy Boen, owner/operator of AB Transmission, in Yakima, Wash., for providing images for this article.

You May Also Like

Solving electronic control problems in today’s automatic transmissions

Special tools are often needed when diagnosing transmission problems and overhauling units.

The modern automatic transmission and attached drivetrain system has many “mechatronic” parts that control and protect the traditional clutches and planetary gears. These devices shift the gears, lock the clutches and regulate the fluid pressures. Most of these items can be diagnosed and replaced while the transmission is still in the vehicle.

How to fix GM 8L45/8L90 no-move and no-pressure conditions

By now you may have heard of, or even experienced, a GM 8L45 or 8L90 transmission with a no-move or no-pressure condition. Conditions of no movement or no pressure after repair have plagued this unit since its inception. Here’s what you can do about them. Related Articles – Are you ready to rock in 2023?

Tasc-Force-December-Figure-1-Pressure-Regulator-Valve-Assembly-Correct-1400
Searching for the source of an unexpected transmission fluid leak

As the installer was pumping fluid into the transmission from the right side of the vehicle, he was having a difficult time getting it full.

techspeakfeature-1400
Transmission slipping in fifth gear: An elusive cause of a common problem

Sometimes, finding the cause of a complaint isn’t as straightforward as one would expect; sometimes, these causes can be very elusive.

December-Shift-Pointers-Figure-1-1400
Stop/start accumulators: What you don’t know can hurt you

It’s no secret that the auto industry is making big moves these days, but while a lot is new, one thing that never changes is that the men and women servicing vehicles need to be learning almost constantly in order to do their jobs safely and effectively. Everybody knows not to touch hot exhaust parts,

Figure-1---Stop-Start-Accumulators-1400

Other Posts

Sonnax introduces input housing forward sleeve kit for GM 4L series

Sonnax has introduced a new input housing forward sleeve kit (part no. 77733-52K), which the company says can increase input housing torque capacity and maintain OE forward piston apply area in GM 4L60, 4L60-E, 4L65-E and 4L70-E transmissions. Related Articles – Rotary introduces XA12 Alignment Scissor Lift – ILI introduces Lubegard engine oil protectant for

Sonnax-77733-52K-600
Sonnax highlights boost valve kits for Aisin Seiki transmissions

The drop-in K1 apply boost valve kit and lockup boost valve kit are available from Sonnax.

Sonnax releases Smart-Tech drum module for TH400 racing applications

At the recent PRI show in Indianapolis, Sonnax announced the release of its Smart-Tech drum module for racing GM TH400 transmissions. Related Articles – Alto releases filter for Nissan GR-6 dual clutch transmissions – Alto introduces steel plate for GM transmissions – GFX introduces new oil pan lines for various GM transmissions According to Sonnax,

Sonnax-34555-01K
Sonnax introduces PR boost valve and o-ringed end plug kits for GM 9T series

Sonnax has introduced drop-in PR boost valve and o-ringed end plug kits for GM 9T45/50/60/65 transmissions. Related Articles – GFX adds new hard part for JF015E, REOF11A – Alto offers filter kit for GM TR-9080 DCT – GFX adds new pump for vintage Powerglide models Pressure regulator boost valve kit #184740-02K restores line pressure performance