6F35 Transmission Problems – Any Serious Issues?

The 6F35 Transmission from Ford is one of the ingeniously designed transmissions from this American car maker. The Transmission made its debut in 2009 when Ford installed it in Ford Escort, Mazda Tribute, and Ford Mariner.

6F35 transmission highlights

• Average lifespan:190,000-210,000 miles
• Reliability Score:High
• Prone to minor issues:Yes
• Price for repair after failure:$1,200-$1,600
• Price for replacement:$4,000-$5,000
• Availability of parts:Average
• Common problems: Fluid contamination, differential issues with 2.0L EcoBoost, wiring problems, overheating, electronic control problems.

The 6F35 Transmission

Ford employed innovative technology to make the 6-gear 6F35 transmission system an upgrade of the 4 and 5-gear transmissions. This, mostly front-wheel Transmission boasts better fuel efficiency while also lowering CO2 emissions.

In effect, this strategy helps improve the gas mileage of the car and also reduce the harmful greenhouse emissions. Notably, the 6F35 is compatible with both two-wheel and all-wheel drive vehicles. 

Ford delivered a sustainable, adaptive, and reliable transmission system by employing advanced technology and materials. They have armed the Transmission with a greater gear span allowing the engine to function at much better optimal combinations of speed and load.

To the keen driver, the 6F35 offers up to 6% better fuel economy as compared to the conventional 5-speeds. This is something many drivers look out for when shopping for a car. In addition, one will notice the sporty acceleration of their car. 

The 6F35 is designed to match the 2.5L L-4 engine. It also works perfectly with the 3.0L V6 engine of the Ford Mariner and Escort.

This Transmission is also preferred because of its lower noise, vibration, and harshness (NVH).

What problems does the 6F35 Transmission have?

The 6F35 Transmission is found on a wide range of cars, and the transmission issues generally faced by most drivers are highlighted here. Some of the highlighted problems are specific to car makes and models. 

1) Sluggish acceleration from 0 to 8mph

Some drivers have reported their cars to get sluggish acceleration from start to 8mph. Other drivers report experiencing the same sluggishness and hesitation feel when the car is at a rolling stop. This problem is caused by a flaw in the Transmission valve body. This problem has been experienced by 6F50 drivers too. 

The solution: The recommended remedy to this problem is to modify the valve body by deleting a hole located on the separator plate. This should be followed by removing the check ball found where the deleted hole was. This procedure should expertly be done because if wrongly done, the car may experience a 2-3 gear shift flare or a loss in reverse. 

2) Fluid overheating

The cooling system of the 6F35 Transmission varies from one car model to the next. In some cars like the Ford Fusion, the cooling system is dogged by overheating issues, making the Transmission perform at less-than-optimal capacity.

In a 1.5L Eco-Boost, for example, you will find Ford has placed the heat exchanger located on a bracket that is attached to the Transmission. All the cooling fluids first enter the heat exchanger making all particulates get trapped in the tight mesh of the exchanger. This problem happens when the moving components found in the Transmission create more friction than the ATF can remove. 

The problem can further be compounded by the external cooler bypass valve failing. This cooler valve is installed in the 2nd generation of the 6F35 transmissions. Due to the fluid inside the aluminum housing not cooling correctly, it becomes darker and less efficient. You can check the condition of fluid in the housing by removing the thermal bypass valve.

The deteriorating condition of the cooler bypass leads to the car experiencing shifting issues, eventually leading to transmission failure. If you are doing a transmission overhaul, it is advisable to replace this cooler.

The solution: Replacing the heat exchanger should solve the overheating issue. However, you can flush the circuit if the blockage is the only hindrance. 

When flushing the cooler circuits, ensure that the cooler bypass valve mentioned earlier is replaced. The valve is not expensive and goes a long way to ensure the system works seamlessly while keeping the warranty intact. The transmission cooling system should be done correctly to avoid experiencing the same problem again. 

To avoid the reoccurrence of this problem, stop or avoid towing heavy loads. The problem will also arise when you drive on mountainous roads frequently. This causes the transmission to shift a lot. The problem can also arise when you drive a lot in stop/go traffic. 

3) Vibration and shudder sound on light acceleration

This problem mainly affected vehicles equipped with all-wheel-drive manufactured in 2009. Some of the cars affected include Ford Taurus, Ford Flex, Lincoln MKT, and Mercury Milan. You may experience some vibration or a shutter in the driveline when you make a tight turn. This issue can further be highlighted by a clunk or a thump sound noise when you press the accelerator slightly.

In many cases, the drivers that have reported this issue say that these symptoms come about when the car is driving uphill and under 40mph. It also happens when the car is towing and under heavy acceleration. 

The solution: There is little you can do to prevent this issue from happening, especially if you can't change the environment you drive in. However, you should install a PTU to help you completely solve the issue. The power transfer unit (PTU), a simplified transfer unit, helps stabilize the car.

4) Erratic shifting, slipping, harsh reverse or drive gear engagement

Many complaints about the 6F35 revolve around erratic gear shifting, slipping between gears, and harsh engagement of reverse or forward gear. You will experience a hard slam when the transmission engages the Drive or Reverse gear. There seems to be a design flaw in the 6F35 transmission, or at least that's what a section of professional mechanics says. 

The solution: Replacement of the whole transmission is sometimes recommended, especially where there is irreparable damage. The aftermarket transmission involves a complete remanufacturing and testing of the valve body, improving the gear shifting, and lubrication for better overall performance.

This process is quite involving and requires an expert as even the system's recalibration and the sensors' resetting are necessary. 

To get to the root of the problem, the transmission control module (TCM) must be tested to ensure that the shift solenoids, pressure switches, and pressure control solenoids are working properly. Because of the intensity of the work involved, you should seek the services of an expert mechanic if you are not one. 

General 6F35 transmission issues and how to repair them

• The torque converter repair- You should replace the worn-out element while repairing the torque converter. You should clean the valve body by changing the paper gaskets and worn rings from the overhaul kit. Overheating and contamination of the ATF lead to the premature wearing out of the torque converter.
• Sensitivity to loads- The 6F35 transmission is repaired using original XT-10-QLV or DEXRON®IV OIL. This is done at the same time while replacing the filter. This transmission has no ATF level gauge, and its level should be tested using the overflow stopper. It is important to know this transmission is very sensitive to ATF levels and to towing heavy loads when the ATF is cold.
• Solenoid issues- The 6F35 transmission solenoids operate at an intensive rate, leading to fast wearing out. Detecting worn-out solenoids can be done using fluid pressure. It can also be done by slipping friction parts and wearing out of the TC clutch. These early signs should help transmission experts at the garage do a minor preventive repair by replacing worn-out rings and rubbers.
• Transmission issues in the long run- Drivers have run into trouble with their 6F35 cars after the car covers over 50,000 miles. Those that have complained of this issue say that their cars had a shift flare on the 1 to 2-gear and 2 to 3-gear shifts. The problem was a casting issue, and the manufacturer issued a remedy to this. Ford also updated the PCM, requiring owners of the affected cars to visit a dealer for an upgrade. For the first-generation owners of the 6F35, a few computer tweaks were required to ensure the car runs smoothly.
• Left half shaft seal leaking- Some 6F35 transmission of the Ford Fusion released between 2010 and 2014 experienced a fluid leak on the left half shaft seal of the system. This was caused by premature wear and tear of the transmission case bushing. To rectify this, you will need to update the case bushing and install an updated half shaft, seal, and case bushing.

Conclusion

The 6F35 transmission was developed through the collaboration between Ford and GM. The transmission proved to be a huge upgrade over the previous 4 and 5-gear transmissions. This transmission has proved robust and convenient because it can be used on two-wheel and all-wheel-drive vehicles.

The overall performance and lifespan of the 6F35 transmission depend on the car's control unit settings and the driver's driving style. All in all, this transmission, despite a few issues here and there, is reliable, better than many, and remains highly competitive in performance.