Some Toyota 4x4 vehicles like the 2007 to 2013 FJ Cruiser or Tacoma may experience what feels like a harsh downshift into first gear only after sitting still in drive. The bump is so pronounced you are looking in the rear view mirror asking yourself, who hit me?
In fact there is a factory TSB about this, reference number T-SB-0046-12. This bulletin calls for a new rear drive shaft to be installed at the tune of about $350 to $550 bucks depending on where and how you buy. This of course is only after you have verified that the rear drive shaft is the problem.
If it is, you may want to inspect the drive shaft for a grease fitting (figures 1 and 2). Apparently the slip yoke gets bound up from being dry. Grease it up and the problem goes away. Both the front a rear u-joints may have fittings as well (figure 3). While fixing the sudden clunk complaint, squeeze some grease into those squeaking joints.
