Background

• Late generation transmissions for the Ford F-150 are the 6R80E 6-speed automatic and the Automatic OverDrive electronic 4R70W and 4R75E 4-speed transmissions. The AOD-E allows the engine to drop 1000 rpm at highway speeds for more fuel-efficient cruising than the standard 3-speed automatics. The 4R70W can generate up to 506-lb.-feet of torque.
  
  

Shift Points

• A common practice among truck owners engaged in heavy work is to make modifications to suit their needs. Although changing differential ratios may increase torque for greater towing capacity, the vehicle's computer needs to be reprogrammed. Changing the differential ratio, for example, from 3.08:1 to 4.1:1 may cause the transmission to change to high gear late and back to low gear too early, according to 2carpros.com. The problem lies with the shift points controlled by the vehicle's computer. The shift points must be reprogrammed to match the new differential ratio.
  
  

OD Warning Light

• Warning lights have a tendency to err on the side of caution and also may not even signal trouble with the transmission itself. The Overdrive light on Ford F-150s may occasionally flicker. A computer code read-out at a Ford dealer may reveal excessive transmission fluid temperature. More often than not, however, the culprit is a $40 faulty sensor instead of a $1,200 tear-down of the transmission, according to fordforums.com.
  
  

1997 Models

• The AOD transmissions in the 1997 F-150 models have been known to leak transmission fluid in to the transfer case, causing shifting problems. Off-roaders are also advised on the 1997 models that the transmission mode switch may short out if water gets into the transfer case, making it impossible to change gears.
  
  

1989-2003 Models

• The 1989 to 2003 F-150s also have been known to have transmission fluid leak into the transfer case. In addition, the torque converter dust plug can fall out, requiring a sealant to keep it in place.
  
  

Shot Torque converter

• Incorrect use of towing can cause significant damage to the automatic transmission. Rocking the F-150 back and forth by quickly shifting from reserve to forward multiple times to gain traction causes enormous stress on the torque converter. Such abuse may result in the owner hearing a loud "bang" followed by the truck not moving forward. If an internal examination reveals metal splinters, the torque converter needs to be replaced.
  
  

Erratic shifting

• Early 1990s F-150s equipped with automatic transmissions have been known to shift erratically or shift abruptly into gear. This is often caused by a faulty lever position sensor or low fluid level.