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1980-1996 Ford F100/F150/F250/F350 Trucks (including 1997 F250HD and F350) and Bronco Transmission, Transfer Case, and Differential Fluid Check

Ford Bronco Digital Manual

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This page is taken directly from our digital online manual 36058 for the 1980 to 1996 Ford F100, F150, F250, and F350 pickup trucks (including 1997 F250HD and F350), plus Bronco SUV, with 3.8L V6, 4.9L/300 cubic inch inline six, and 255, 5.0L/302, 5.8L/351, 400 and 460 cubic inch V8 engines. Every moving part of your truck needs lubrication. We all check and change our engine oil periodically, but the transmission, differentials, and transfer case need checking too. Checking them is more difficult than just pulling a dipstick, but you don't have to check them that often. Check the ATF level in the automatic transmission every 6 months, or when you change the engine oil. If you have a manual transmission, check once a year, along with the oil levels in the rest of the driveline. But remember, if you off-road, check after any trip that involves driving through water that comes half way up your tires to avoid water contamination.


Automatic transmission fluid level check (every 3000 milesor 6 months)

  1. The automatic transmission fluid level should be carefully maintained. Low fluid level can lead to slipping or loss of drive, while overfilling can cause foaming and loss of fluid. Either condition can cause transmission damage.
     
  2. Since transmission fluid expands as it heats up, the fluid level should only be checked when the transmission is warm (at normal operating temperature). If the vehicle has just been driven over 20 miles (32 km), the transmission can be considered warm.
    You can check the transmission fluid level when the transmission is cold. However, the fluid level is normally checked with the transmission warm to ensure accurate results. If the vehicle has not been driven for over five hours and the fluid is about room temperature (70 to 95-degrees F), the transmission is cold.
    Caution:  If the vehicle has been driven for a long time at high speed or in city traffic in hot weather, or if it has been pulling a trailer, an accurate fluid level reading cannot be obtained. Allow the transmission to cool down for 30 minutes.
     
  3. Immediately after driving the vehicle, park it on a level surface, set the parking brake and start the engine. While the engine is idling, depress the brake pedal and move the selector lever through all the gear ranges, beginning and ending in PARK.
     
  4. Locate the automatic transmission dipstick tube at thepassenger’s side of the engine compartment  (see illustration).

 

The automatic transmission fluid dipstick is near the firewall, to the left of the engine

Illustration 7.4 The automatic transmission fluid dipstick is near the firewall, to the left of the engine

 


  1. With the engine still idling, pull the dipstick from the tube, wipe it off with a clean rag, push it all the way back into the tube and withdraw it again, then note the fluid level.
     
  2. If the transmission is cold, the level should be in the room temperature range on the dipstick (between the two circles); if it’s warm, the fluid level should be in the operating temperature range (between the two lines)  (see illustration). If the level is low, use a funnel to prevent spills and add the specified automatic transmission fluid through the dipstick tube.
    C4, C6, AOD
         1980                           DEXRON II
         1981 on                     MERCON
    C5                                    Type H
    E4OD and 4R7OW        MERCON

 

If cold, the level should be between the two circles - if warm, the level should be between the two lines

Illustration 7.6 If the automatic transmission fluid is cold, the level should be between the two circles - if it’s at operating temperature, the level should be between the two lines

 


  1. Add just enough of the recommended fluid to fill the transmission to the proper level. It takes about one pint to raise the level from the low mark to the high mark when the fluid is hot, so add the fluid a little at a time and keep checking the level until it’s correct.
     
  2. The condition of the fluid should also be checked along with the level. If the fluid is black or a dark reddish-brown color, or if it smells burned, it should be changed (refer to Section 36 ). If you are in doubt about its condition, purchase some new fluid and compare the two for color and smell.

Driveline lubricant level checks (every 15,000 miles or 12 months)

Manual transmission lubricant

  1. Raise the vehicle and support it securely on jack stands.
     
  2. Locate the fill plug at the side of the transmission case(see illustration). Clean all dirt from the area adjacent to the plug. Slowly withdraw the plug. If oil starts to drip out as the plug is withdrawn, immediately reinsert it into the transmission. The level is correct.

 

The manual transmission fill plug and drain plug are located on the side of the transmission case

illustration 22.2 The manual transmission fill plug and drain plug are located on the side of the transmission case

 


  1. Remove the fill plug if the oil does not run out, and check to see if the level is up to the bottom of the plug hole. If it is not, fill the transmission through this hole until it is.
     
  2. Visually check the transmission for any signs of leakage at either the front or rear seal or near such components as the speedometer drive. 

Transfer case lubricant (4x4 models only)

  1. To check the oil level in the transfer case (on 4 x 4 models), locate the fill plug on the transfer case. Usually on the rear driveshaft side(see illustration).

 

The transfer case fill plug (A) and drain plug (B) are usually located on the rear of the transfer case

Illustration 22.5 The transfer case fill plug (A) and drain plug (B) are usually located on the rear of the transfer case

 


  1. Check the transfer case oil level in the same manner as the manual transmission.

Differential lubricant

  1. Differentials are checked by withdrawing the fill plug from either the rear cover or from the side of the differential assembly  (see illustrations)  . Use the same procedure as was used to check the oil level in the manual transmission.

 


Typical location for cover-mounted differential check/fill plug (4WD front axle housing shown)

Illustration 22.7a Typical location for cover-mounted differential check/fill plug (4WD front axle housing shown)

 

Typical location for side-mounted differential check/fill plug

Illustration 22.7b Typical location for side-mounted differential check/fill plug