I have 70K miles on my 2001 truck. My back belts wouldn't lock if the engine was running or not. My front belts locked with the engine running or not.

 

Thanks for taking the time to test it.. Did you test just by yanking them, or did that include pulling them all the way out? Also curious if you pull them all the way out, if they will only retract.

 

Everything works as new. They pull all the way out and gave them a hard yank on all 4 at different lengths of the belts. They all retract to original positions. The front lock every time I pulled on them and I got the back ones to lock once with a real hard and quick pull. If fat like I am the front seat belts are just long enough to click with the seat all the way back. Every other car I've never had a problem of them going around. Seat belt extensions works nicely. I put my grandsons child's seat in the back, pull on the belt to take slack out and trust it to lock when needed.