A vehicle that I had to perform a transmission repair had the most horrendous punch-you-in-the-face smell you could ever imagine. I rolled every window down with little relief. The source—a large pile of fish heads in the back seat baking in 100 degree summer heat. Can’t explain.

A mini-van came in with a “wing window” broken. The gentleman repaired it with concrete and wire mesh. I guess it would never break again.
The competing dealership across the street from us opened up the trunk of a vehicle that came in for service and discovered a human corpse. Oops, meant to take that out?

Through the years we found bricks of drugs, several adult female “toys”, many various guns and weapons, bottles of liquor, fast food remnants and wrappers, used diapers and clothes piled so high that only the driver's seat was visible and a live snake.

One technician (now retired) working behind the dash of a Lincoln found a brown paper bag with $60k dollars tightly wedged behind the glove box. Being an honest man (yes, they are out there) found the customer in the waiting room. The man was a sharp dressed individual wearing a pin-striped suit. The technician told him it would be a good idea to “take his valuables with him”. The guy gave him a perplexed look. The technician brought him over to his car and showed him the bag of money and where he found it. The guy took one look at it laughed and shook his head saying,”I thought this was stolen from me. I guess I killed that guy for nothing.”

I saved the best for last. Strange, but true. A lady dropped off her car for some routine service. A day later she and her daughter come to pick it up. She and her daughter (they being very fluffy if I can say) got into the car, but did not leave for some time. We heard some commotion, but could not hear what was the issue. A minute later, they stomped out of the car, swung the door open, fists clenched and red-faced demanded to know who shrunk their car?!!! Yes, you read this correctly. We just stared back speechless. She gave us an ultimatum to “put it the size that we dropped it off or you will hear from my lawyer.”

https://www.quora.com/As-a-car-mechanic-what-is-the-craziest-discovery-you-have-found-on-an-automobile