Some 2003-2020 Lincoln Navigator vehicles equipped with a TOD transfer case may exhibit a grinding/clicking/ratcheting noise from the front wheel area. This may be due to partial engagement of the integrated wheel ends (IWE). The vehicle may be equipped with a mode select switch (MSS) that includes a 4-wheel auto (4A) option. To correct the condition, locate the vacuum supply line between the source vacuum and the IWE check valve. Remove the vacuum supply line and install vacuum caps at the IWE check valve and the vacuum source. The vacuum line cap kit is available as P/N W716372-S300.
Note the vacuum source (bottom left of blue line).\
Remove and discard the vacuum line and install vacuum caps from the kit at the source vacuum and at the IWE check valve.
