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All Ford Overdrive Problems & Reliability Issues

What kind of problems does a Ford with Overdrive normally have? In this blog, we’ve outlined all the most important things you should watch for when you’re in the market for a Ford with Overdrive. In the rest of the article, we’ll discuss every single problem in detail. Furthermore, we’ll tell you how to identify it, fix it and how much it costs to fix. Read on!

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Also read: The Complete Cost Of Maintaining A Ford

1. TV Cable Out Of Adjustment

First introduced in 1980, the AOD or Automatic Overdrive is a fairly beneficial and popular transmission system employed in most Ford cars and trucks.

The Automatic Overdrive is a simple mechanism that allows your Ford to maintain a stable speed while you are driving and decreases the engine speed by shifting your vehicle into a gear ratio higher than the drive gear. For instance, this transmission automatically goes into overdrive at high speeds and uses a lower gear ratio that can help you save big on gas.

Although reasonably reliable and rugged, the Ford Overdrive has some serious setbacks, including the TV cable, which can go out of adjustment.  

The AOD is a fully hydraulic transmission, has no electronic controls, and is completely controlled via hydraulics. The two inputs controlling the transmission are TV (Throttle Valve) pressure and governor pressure off the output shaft. The TV pressure is controlled by a simple cable (or rod, in the case of older models) that goes up to the throttle body (or carburetor if your Ford has it).

To know when to shift the gear, the AOD transmission in your Ford must constantly receive input from the engine through the throttle valve cable. This cable has to remain adjusted properly, or it may cause shifts at all the wrong times. This misalignment of the TV cable ultimately affects your Ford’s driving experience, fuel economy, and performance.

To properly adjust the throttle valve or the TV cable, you need to alter the tension with a pressure gauge and then test it on the road to check the adjusted settings. If the settings weren’t correct, then the Ford Overdrive transmission might require a complete overhaul.

To adjust the TV cable on your own, you can follow these steps –

  1. Push/pull the TV cable and block assembly out of the throttle arm rubber grommet.
  2. Have somebody floorboard the accelerator pedal from inside the vehicle. When the pedal is floored, push on the throttle body arm to ensure it is bottomed (wide open against its stop), adjust the throttle cable, if required.
  3. Next, push the locking tab up through the adjustment block using a pocket screwdriver, such that the locking tab stands up next to the clevis pin.
  4. While the pedal is floorboarded, pull the TV rail towards the end of the cable, and simultaneously, engage the clevis firmly into the throttle arm grommet with the other hand. Engaging the clevis locks the tab automatically by pushing it into the block.
  5. Now, pull the block adjustment assembly out of the grommet: place a mark on the rail with a blade or knife up against the adjustment block. This is the Max TV mark.
  6. Now, place another mark 5/16” from the max mark out on the rail (Use a 5/16 pan bolt for a gauge). This is the Min TV mark.
  7. Now, place another mark midway between the min and max mark. This is the Mid or Average mark.
  8. Next, unlock the adjustment tab. Set on Mid mark and lock tab (drive it down into block).

After adjusting, perform a road test. If the above process seems a bit overwhelming to you, then consider taking your Ford to the service station to have the TV cable appropriately adjusted.

2. Input Shaft Failure

Another common issue that can come with the Ford Overdrive is the failing of the inner input shaft. The AOD transmission on the Ford employs two input shafts to operate the gears. The split torque design of the transmission has a hollow shaft that houses another smaller shaft known generally as the ‘Inner Input Shaft.’

Both these shafts run different separate sets of sun gears. Ford calls it a 60/40 split torque design in which the larger hollow shaft runs first, second and reverse gear, and the smaller inner shaft takes almost 60 percent of the workload in running the third gear and overdrive.

The inner shaft, which is in charge of operating the third gear and overdrive, can most of the time be under a lot of stress, which can cause it to fail.

Reportedly, in most cases, when the input shaft fails, it is not accompanied by any bang or noise. But instead, you will notice a complete loss of power (as if the car is neutral) when you change the gear from third to fourth. This indicates a problem with the inner input shaft in your Ford’s AOD.

If the inner input shaft on your Ford Overdrive is damaged, it should be replaced to ensure the proper functioning of your vehicle. The shaft is only held by the socket and the torque converter at the ends and nothing else, making it easy to replace.

Also, replacing the broken inner shaft with a new hardened shaft is essential to avoid this situation in the future. You can consider going to the Ford service station to have the shaft replaced with an upgraded one to fix the problem. 

3. Overdrive Servo Retaining Clip Snapped

A not-so-frequent but severe problem that can come with the Ford Overdrive is the failure of the servo retaining clip.

Common signs indicating an issue with the servo retaining clip include –

  • No overdrive
  • Unable to engine brake into the second gear
  • Car shifts right into neutral
  • If overdrive is turned off, the car drives normally within the first three gears

To detect any problem with the servo retaining clip, you can remove the transmission pan to look for any broken parts. If nothing is found, you can check the valve body where the overdrive servo retaining clip might have lodged itself into a valve in the valve body. 

To fix this issue, replace the broken clip with a new one. A new overdrive servo retaining clip is relatively inexpensive, costing around $2, and the whole kit can cost anywhere around $30-$50 in the United States.

To check and replace the damaged pin, you can follow the following steps –

  1. Remove the valve assembly. It is an easy task and does not require any special tools. But there are a total of 24 bolts, some of which must be put back into the exact location due to the different lengths of the bolts.
  2. Next, you would have to remove the solenoid valves, bridge connector, and the shift lever detent spring. Again, it is not difficult, but considering the parts are small, handling and reassembling them can be a bit tricky.
  3. Afterward, once the valve body is detached, you need to carefully remove the gasket assembly as well.   
  4. Once the gasket assembly is out, you can find the spool valve that might be jammed with a broken piece of the clip.
  5. Moving forward, you would now have to carefully remove the old servo retaining clip that holds the overdrive servo. But since it might have broken, chances are you can’t use snap ring pliers to remove it. Instead, remove it using a screwdriver and a pick.
  6. Now, carefully replace the put a new servo retaining clip.

While following this procedure, ensure no part of the valve body gets damaged; otherwise, it can be expensive. If the above process is too much, you would have to take your Ford to a service station to get this issue fixed.  

4. Overdrive Off Switch Not Working

On certain Ford Vehicles, the problem with the overdrive switch not working is common.

When this occurs, the car won’t come out of overdrive even when you turn off the overdrive using the switch. The transmission might normally shift through all gears, both up and down. Additionally, even on the highways, when the vehicle is at high speed, the overdrive on your Ford will work just fine. But when you make a downshift by turning off the overdrive, it just won’t work. 

To identify this problem, you can also notice the ‘OD Off’ light would not be illuminated anywhere on the dashboard when you push the O/D off button.

The problem with the O/D button usually occurs due to some electrical fault, disturbing the signal from the O/D button to the ECU (Engine Control Unit) and the transmission. In some cases, it is also possible a blown fuse is responsible for this problem. So, you must check the fuse box in your Ford vehicle for any faulty fuse.

You can also pop open the shift lever cap and remove the O/D switch to check the power distribution there. Sometimes, the wire/s of the overdrive switch can get damaged or break at the base of the shift lever. If the wires are broken or worn, they should be replaced, or a new replacement shifter will come with the harness as part of the assembly.

To accurately identify and resolve the root of the problem, it is recommended to consult a Ford technician.

5. Transmission Dropping Out Of Overdrive

Another common problem that many Ford owners experience is that their transmission keeps dropping out of overdrive. In most cases, the overdrive will work fine below the speed of 50 to 60 mph. But as soon as the vehicle’s speed increases to more than 60 mph, the transmission will continually drop out of overdrive and will sometimes also shift back into overdrive.

If the transmission in your Ford is repeatedly coming out of overdrive and going back into overdrive, then either there is an inner problem with the transmission system, or the downshift solenoid has an internal leak.

Downshift solenoid is all about the pressurized hydraulic fluid that assists in smooth gear changes in your Ford. The transmission solenoid directs the transmission fluid to the valve body to engage the right gear whenever a gear is changed. The downshift solenoid, in simple words, regulates the change from a higher gear to a lower gear.

Since it is an electronically controlled mechanical part allowing fluid movement to engage the intended lower gear, you can experience an erratic shift if it goes bad, and transmission can continually drop out of overdrive.

To fix this problem, you must check the downshift solenoid for any issues and see if it’s functioning properly. To do this, slow down your Ford and check if the RPMs slightly increase as the vehicle descends to stop.

If the RPMs are not increasing as the vehicle slows down, there is an internal issue with the downshift solenoid. To solve this, you should consider replacing the downshift solenoid.

Besides, if the RPMs are rising as the vehicle slows down, the problem is with an internal transmission part. To solve this, it is recommended to take your Ford to the service station and have the issue inspected by an expert.