If I understand correctly, the pop you heard was due to the tapered stud being wedged in the hole. It takes a lot of pressure to break it free. The new one will gradually become wedged tighter as you tighten the nut. Because of the threads, it doesn't take much pressure on the wrench to tug really hard on the stud. The main thing to watch is once you reach the required torque on the nut, do not loosen it to line up the hole for the cotter pin. Always tighten the nut to the specified amount, then go some more until you can get the cotter pin through.
The foam insert is just there to help keep dirt and water out.
Thursday, March 3rd, 2011 AT 6:48 PM