I pulled pretty hard? I really don't have a definitive answer, but they're in there to stay. I was perplexed that no one had an answer to this. There had to be another type stem back in the day but I had no luck finding one that would fit the bill. I have a commercial shop with loads of truck supplier catalogs, no luck. Got 415 to work as you can see. Maybe you are using to much lube, more friction may help?