Mercedes-Benz Transmission Leak Checking

m2 mm 26.07.000
  1. Park the vehicle on a level surface. Apply the parking brakes and chock the rear tires.
  2. Check for signs of leakage at the breather. See Fig..

    Note: The transmission is shown from the left-hand side.

    1. Shift Lever Cap Seal

    2. Breather

    3. Output Shaft Radial Seal

    4. Countershaft Cover Plate

    5. Transmission Fluid Fill Plug

    6. Transmission Fluid Drain Plug

    7. Gear Case Seals

    8. Clutch Secondary Cylinder

    9. Input Shaft Radial Seal

    Fig. 1, Mercedes-Benz Transmission Leak Check

    1. If leakage is found, check the breather for a missing cap. Replace the cap if necessary.
    2. Check the fluid level at the fill plug. If the level is too high, correct the fluid level.
  3. Check for signs of leakage at the cap seal on the shift lever. If the cap seal is damaged, replace it.
  4. Check for signs of leakage at the radial seal on the output shaft. If leakage is found, remove the output yoke (end yoke) and replace the seal. For procedures, see General Information, SmartShift™ Transmission Shift Control of the Business Class® M2 Workshop Manual .

    5. Note: There are two cover plates on the countershaft, one at the front and one at the rear.

  5. Check for signs of leakage at the rear cover plate on the countershaft (next to the output yoke). If leakage is found, check the torque on the cover-plate bolts and check the flat seal for damage.
    1. If the flat seal is damaged, replace it.
    2. If the cover-plate bolts are too loose, tighten them 18 lbf·ft (25 N·m). If the cover-plate bolts are too tight, replace the flat seal and tighten to 18 lbf·ft (25 N·m).
  6. Check for signs of leakage at the transmission fluid fill plug. If leakage is found, check the torque on the plug and check the aluminum gasket for damage.
    1. If the gasket is damaged, replace it.
    2. If the fill plug is too loose, tighten it 42 lbf·ft (57 N·m). If the fill plug is too tight, loosen it, then tighten it to 42 lbf·ft (57 N·m).
  7. Check for signs of leakage at the transmission fluid drain plug. If leakage is found, check the torque on the plug and check the aluminum gasket for damage.
    1. If the gasket is damaged, replace it.
    2. If the drain plug is too loose, tighten it 42 lbf·ft (57 N·m). If the plug is too tight, loosen it, then tighten it to 42 lbf·ft (57 N·m).
  8. Check for fluid dripping at the gear case seals. If substantial leakage is found at either location, replace the transmission.

    9. Warning: Clutch hydraulic fluid (DOT 4 brake fluid) is hazardous. It may be a skin irritant and can cause blindness if it gets in your eyes. Always wear safety glasses when handling clutch hydraulic fluid or bleeding hydraulic lines. If you get clutch hydraulic fluid on your skin, wash it off as soon as possible.

    Note: Weeping or sweating seals are not cause for transmission replacement.

  9. Check for signs of leakage at the clutch secondary cylinder.

    Notice: Do not spill clutch hydraulic fluid (DOT 4 brake fluid) on the cab paint. Clean it off immediately if any is spilled. DOT 4 brake fluid can damage paint.
      1. If leakage is found on the secondary cylinder body, check the fittings and hose for damage.
      2. If leakage is found on the piston seals, replace the secondary cylinder and bleed the clutch hydraulic system. For detailed instructions, see General Description, Eaton Fuller Solo Clutches of the Business Class® M2 Workshop Manual .
      3. If the secondary cylinder fittings and/or the hose are damaged, replace them.
      4. Check the torque on the secondary cylinder mounting capscrews. Tighten them 13 lbf·ft (18 N·m).
      5. If any leakage of clutch hydraulic fluid is found, check the fluid level in the reservoir, and add fluid if needed. For detailed procedures, see General Description, Eaton Fuller Solo Clutches of this manual.

      Note: There are two cover plates on the countershaft, one at the front and one at the rear.
      1. Check for signs of leakage at the clutch bell housing. If leakage is found, check the radial seal on the input shaft, the front cover plate on the countershaft (inside the clutch bell housing), and the rear radial seal on the crankshaft.
        1. If the radial seal on the input shaft is leaking, replace the radial seal. For procedures, see General Information, SmartShift™ Transmission Shift Control of the Business Class® M2 Workshop Manual .
        2. If the cover plate on the countershaft is leaking, replace the cover plate. Apply liquid gasket (Loctite 518) to the new cover plate when installing it.
        3. If the rear radial seal on the engine crankshaft is leaking, replace the rear radial seal. For procedures, see the engine manufacturer's manual.
      2. Remove the chocks from the tires.
      Note:
      Parent topic: Transmission
      Document Number: 0000120826
      Manual Publication Date: 2024-05-23
      Topic Publication Date: 2024-11-06