Mack | Mack Transmission T318 (L)(LR)(21)(L21)(LR21) - Transmission Maintenance

Note: Perform oil level check when the oil is at operating temperature. The vehicle must be in a level position, both front-to-rear and side-to-side.

• Check the transmission oil level at the intervals specified in the Maintenance and Lubrication Manual (TS494).

Magnetic Filter Plug (Not for Level Check)

• Pass
• Flag
• Fail

Oil Filler and Check Plug

• Pass
• Flag
• Fail

The oil must be level with the bottom of the filler plug hole as determined by feel or by visual inspection.

Warning: Be careful not to burn your finger in hot gear oil when checking the oil level in the transmission.

If oil can only be felt by reaching the finger down into the unit, the oil level is too low.

Incorrect Oil Level

Reinstall and tighten the oil filler plug (Figure 55) as follows:

• Check that the O-ring on the plug is not cut or damaged.

• Install the plug and tighten to 41–48 N•m (30–35 lb-ft) of torque.

Caution: DO NOT exceed 48 N•m (35 lb-ft) as plug can seize, resulting in damage to the transmission case when attempting to remove the plug.

Caution: Preserve the environment! Drained gear oil is classified as a hazardous toxic material which must be recovered, handled, stored and disposed of according to applicable State or Federal guidelines.

Change the oil at intervals specified in the Maintenance and Lubrication Manual (TS494).

Before draining oil from the transmission, the oil should be at normal operating temperature.

• Pass
• Flag
• Fail

Remove the magnetic drain plug (Figure 58) from the bottom of the transmission main case and drain the hot oil into an industry-approved recovery container.

• Pass
• Flag
• Fail

Remove the oil filler plug (2) (Figure 59), then fill the transmission using specified oil until the oil is level with the bottom of the filler plug hole (also see Figure 56). Do NOT overfill.

• Pass
• Flag
• Fail

Note: MACK-approved lubricants can be found on the internet at www.macktrucks.com, then click on the PARTS AND SERVICE category.

Reinstall and tighten the oil filler plug as follows:

• Check that the O-ring on the plug is not cut or damaged.

• Install the plug and tighten to 41–48 N•m (30–35 lb-ft) of torque.

Caution: DO NOT exceed 48 N•m (35 lb-ft) as plug can seize, resulting in damage to the transmission case when attempting to remove the plug.

Caution: Be sure to add oil to the transmission through the filler hole, NOT the magnetic filter plug hole. Damage to the transmission and seals may occur due to overfilling. The magnetic oil filter hole is higher on the transmission case than the filler hole.

Remove the magnetic oil filter plug and clean the magnet in the plug every time the oil is changed. Reinstall the magnetic plug. Tighten the plug to 27–31 N•m (20–23 lb-ft) torque.

• Pass
• Flag
• Fail

The T313–T318(L)(LR)(21)(L21)(LR21) transmissions have one air breather, located on the main case shift cover.

• The air breather should be removed and cleaned with a suitable solvent every time the oil is changed.

• Also check to be sure that airflow through the breather is unobstructed.

• Reinstall breather into the main case shift cover and tighten until snug.

The optional three-position (compound neutralizing) range shift cylinder contains a breather vent screen which should be cleaned any time the main case shift cover is cleaned. The following figure shows the breather vent removed (1) and installed (2). Check the breather vent for free airflow. Clean or replace as necessary.