Buick: Oops, wrong bolt
Some 2011 Buick Regals equipped with the AF40-6 automatic transmission may experience a “loss of movement” or no transmission engagement in Drive or Reverse gears and may only have a creep effect as engine rpm is increased.
Other complaints may include transmission slipping, whine noise, delayed engagement or harsh engagement.
The problem may be traced to incorrect torque converter clutch bolts installed at the factory. The incorrect bolt is too long and features the wrong thread pitch, which can cause damage to the TCC mount pad threads, clutch lining and front cover.
The incorrect bolt is M10 x 1.5 x 15mm (featuring an 18mm hex head and no washer). The correct bolt is M10 x 1.25 x 13.8mm, with a 17mm hex head, with a flat washer.
Remove the starter. Remove all five torque converter mounting bolts, and inspect the bolts for signs of thread damage. If any bolts show signs of damage, closely inspect the torque converter mounting pad threads for damage, including witness marks caused by the incorrect bolt length.
If torque converter mount pad thread damage is confirmed, Buick recommends replacing the complete transmission assembly.
The correct torque converter mounting bolts are available (package of five) under P/N 09180138.