Lexus GX470 2004 Repair Manual page 483

DRIVING TIPS
3. When mounted in the ball mount, the threaded ball shank
must protrude beyond the bottom of the lock washer and nut
at least 2 threads. The trailer ball shank must be matched to
the ball mount hole diameter size.
NOTICE
Only use a ball mount attachment specified for the
Lexus GX470.
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