The 4L60E bell housing contains a total of six bolts. It is important to secure them tightly as they are used to hold the transmission in place and keep it from shifting or moving around while the engine is running. The bolts should be tightened with a torque wrench to ensure proper tension, typically between 18 ft-lbs and 30 ft-lbs depending on the make and model vehicle you have. You can also use thread locker adhesive on each bolt before tightening it down for added security, however this isn't necessary unless you're dealing with higher vibration levels such as off roading or racing applications. It's always best practice to refer to your owner's manual for specific instructions regarding installation of any part related to your car or truck.