Ford F-150: Why is My Transmission Slipping?

You hit the gas, the engine revs, and the truck goes... Nowhere? You have transmission trouble. Read on to figure out what those issues might be.

By Pizzaman711 - October 23, 2014

"Slipping" is the sensation that your transmission isn't connected to your engine when you press the accelerator. This happens in manual transmission vehicles when the clutch wears out and loses grip intermittently. The F-150's transmission has been automatic only since 2004, but "slipping" still happens for a number of reasons. This could be a quick and cheap fix, or could mean you need a new transmission. If I can give you one piece of advice, it’s to stop driving the truck as soon as you feel something wrong with the transmission. Prolonged driving can cause excessive damage to an already weakened transmission.

Step 1 – Check DTC Codes

The first step to diagnosing is checking your DTC codes. To do this you’ll need an OBD/OBD II Scanner or a visit to your local dealership or auto parts store. Even if your light isn’t on yet, a code could still be stored from the truck trying to apply it’s adaptive learning to fix the problem.

Once you have the code if it’s not on the list below, a quick Google search or call to your dealership will give you more information on both what the problem is and how to solve it.

4R70E & 4R75E DTCs for slipping transmission

Diagnostic Trouble CodeFailing ComponentDetailSymptoms
P0102, P0103, P1100, P1101 Mass Air Flow Sensor (MAF) The Mass Air Flow sensor in your truck isn't working correctly, causing the transmission to misbehave Incorrect reading from the MAF could result in all sorts of transmission weirdness. Soft shifting, hard shifting, odd shift points, etc.
P0705, P0708 Transmission Range sensor (TR) TR Circuit failure Harsh shifts. Stuck in D or 2.
P0712, P0713 Transmission Fluid Temperature (TFT) P0712= sensor circuit grounded
P0713= sensor circuit open
Hard shifting.
P0715, P0717, P0718 Turbine Shaft Speed Sensor (TSS) Signal from TSS dead, intermittent, on noisy Hard shifts
P0720, P0721, P0722 Output Shaft Sensor (OSS) Signal from OSS dead, intermittent, on noisy Hard shifting, abnormal shifting, slipping,
P0731, P0732, P0733, P0734, Shift Solenoid A/B Shift Solenoid A/B failure or internal transmission failure No gear in 1, 2, 3, 4 (respectively)
P1714, P1715 Shift Solenoid A/B P1714= SSA mechanical failure
P1715= SSB mechanical failure
Solenoid is either stuck closed or open due to a physical failure. Replace them.
P0740, P0743 Torque Converter Clutch (TCC) TCC solenoid is failing or TCC is slipping excessively. Transmission Warning light may flash. Engine might stall in D at low speeds or never engage.
P0741 TCC TCC is slipping excessively due to internal, mechanical issues. Slipping transmission
P0748, P0963 Electronic Pressure Control sensor (EPC) EPC solenoid short Limited torque, slipping transmission, or harsh shifting if the circuit is stuck open.
P1728 Transmission Slip Error Truck computer senses excessive slipping Transmission is slipping, TCC operating erratically
P1740 TCC TCC solenoid mechanical failure Stalls in D and 2, or torque converter never applies
P1741 TCC Excessive TCC engagement issue Engine rushing/oscillation in 3rd gear. TCC is slipping
P1742, P1743 TCC TCC solenoid has failed, or the TCC itself has failed Hard shifting
P1744 TCC Truck senses extra slippage from the TCC Slipping transmission
P0962, P1747 EPC EPC solenoid malfunctioning (short circuit) Minimum EPC pressure, reduced torque, slippage
P1760 EPC EPC solenoid signal dead Reduction in torque

6R80 DTCs for slipping transmission

Diagnostic Trouble CodeFailing ComponentDetailSymptoms
P0715, P0716, P0717 Turbine Shaft Speed Sensor (TSS) short circuit, noisy or lost signal, no signal May cause Check Engine Light, will trigger Transmission Warning Light, inability to shift from 3rd, hard shifts, "slipping" transmission/No TCC engagement
P0720, P0721, P0722, P0723 OSS Sensor short circuit, noisy or lost signal, no signal Check Engine Light, hard shifts, "slipping" transmission/No TCC engagement
P0731, P0732, P0733, P0734, P0735, P0729 Transmission error P0731 = 1st gear
P0732 = 2nd gear
P0733 = 3rd gear
P0734 = 4th gear
P0735 = 5th gear
P0729 = 6th gear
Missing gear. Engine flare in missed gear, hard shifts, TCIL
P0740, P0741 TCC circuit failure, circuit open Slipping shifts, harsh shifts, no shifts, Triggers "Limp home mode," Transmission Warning light, and maybe Check Engine Light.

P0781, P0782, P0783, P0784, P0729

Shift Errors P0781 = 1st-2nd gear
P0782 = 2nd-3rd gear
P0783 = 3rd-4th gear
P0784 = 4th-5th gear
P0729 = 5th-6th gear


These codes indicate shifting errors. You may be stuck in gear and have strange shifting from one gear to another.
P0960, P0961, P0962, P0963 Line Pressure Control Solenoid The line pressure control solenoid is shorting out. Hard shifts, Transmission Warning Message.

Step 2 – Check Your Transmission Fluid

You’ll need to check it while the truck is running and the transmission is warm, usually a 1 - 2 mile drive is enough to warm it.

If the fluid is low, top it off. Likewise if it’s overfilled, drain some out. If the fluid is brown or smells burnt, it needs to be changed. If the fluid is foamy and thick, then there's engine coolant or water in your transmission fluid. You'll need to rebuild the unit.

(Related Article: How to Check Your Transmission Fluid - Ford-Trucks.com)

Figure 1. Make sure the quality of your transmission fluid is up to snuff. The closer it is to pink and clear, the better.

Step 3 – Test Transmission Pressure

Testing your transmission pressure will help identify what component of your transmission is actually failing. This is only necessary for the 4R7xx series of transmissions. You will need a:

  1. Transmission pressure gauge
  2. Basic socket set

The steps are as follows:

  1. Connect the gauge to the line pressure tap
  2. Start the engine, let idle, and check the pressure
  3. Turn off the truck and compare results to chart below
ApplicationTransmission RangeIdleWOT
EPC Line Pressure EPC Line Pressure
All P, N 5-40 psi (34-276 kPa) 40-100 psi (276-689 kPa) N/A N/A
(D) 2, 1 5-40 psi (34-276 kPa) 40-100 psi (276-689 kPa) 100-115 psi (689-793 kPa) 170 - 230 psi (1172-1586 kP)
R 25-30 psi (172-207 kPa) 70-125 psi (483-862 kPa) 85-95 psi (586-655) kPa 250-300 psi (1124-2068 kPa)

If the pressure is not within specification you’ll need to check the EPC pressure. The steps are as the same as above with the exception of you connect the gauge to the EPC pressure tap instead. If the EPC pressure is not within spec you can move onto a pinpoint test. The chart below can give you a better location of where to start with the pinpoint test.

Test ResultsPossible Source
High pressure at idle Wiring harness
EPC solenoid
Main regulator valve
Low at idle Low transmission fluid level
Control Bodies
Tranmission pump leaking fluid
Damaged transmission gaskets
Leaking transmission case
Stuck main regultor valve
Low in park only Transmission valve body
Low/Reverse Servo
Low in reverse only Seperator plate
Low/Reverse Servo, valve bodies
Reverse clutch
Low in neutral only Valve body damaged
Low in overdrive only Forward clutch damaged
Valve body damaged
Low in 1st only Forward clutch damaged
Valve body damaged
Low/reverse servo damaged
Low in 2nd only Intermediate clutch damaged
Forward clutch damaged
Valve body damaged

2011 and newer trucks with the 6R80 transmission have no way to test transmission fluid pressure. However, the sensors will tell you if something is wrong and likely put the truck into "limp home" mode.

(Related: How to Line Pressure Test Your Transmission - Ford-Trucks.com)

Step 4 – Drop the Transmission Pan and Valve Body

Pro Tip

We recommend attempting the next few steps with caution. They all require accessing the transmission's valve body and have the potential to cause major headaches (like ruining a transmission) if performed incorrectly.

Lower the transmission pan and valve body and inspect for debris and clogs. Clear any clogs you find. Fine metal dust is normal and nothing to be concerned about, however bigger pieces of metal are a problem. The bigger they are, the worse it is. You will need to completely rebuild your transmission if you find big pieces of metal. Even if you replace the one part that failed, there's no telling what else it damaged. I recommend having a mechanic do this as there’s a lot of small things that can be messed up.

F-150 transmission pan
Figure 2. This pan is full of metal shavings meaning there is a mechanical failure in the actual transmission.

Step 5 – Inspect Transmission 1-2 Accumulator

This will require a vehicle lift. You will need to remove the transmission 1-2 accumulator and inspect for any damage or worn out pieces, and replace it if any are found. To remove it you’ll need to:

  1. Put vehicle on lift with the transmission in neutral
  2. Drain the transmission fluid and remove the pan and filter
  3. Compress the 1-2 accumulator piston and remove the retaining ring
  • F-150 4R75E Valve Body
    Figure 3. The 1-2 accumulator piston is circled in red here.
  • F-150 Accumulator 1 Diagram
    Figure 4. F-150 accumulator 1 Diagram

You will now need to break it down and check the parts:

  1. Remove the cover
  2. Remove the inner and outer springs
  3. Remove the piston
  4. Remove the upper spring
1-2 Accumulator from 4R75E transmission
Figure 5. 1-2 Accumulator piston from 4R75E transmission

Step 6 – Rebuild Transmission

If all else fails and you can’t pinpoint an exact problem, you will need to have the transmission rebuilt. I recommend having a mechanic who specializes in transmissions do this work. A full rebuild will cost you around $1000. It is not a cheap repair and definitely not one you want to pay for twice if it’s done wrong. Something to consider is that it may be cheaper to buy a used transmission that’s already rebuilt and have that installed versus rebuilding your current one.

Featured Video: Why is My Transmission Slipping?

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