According to Jim Recap: The Truck
Cheryl helps Ruby and Gracie make a monstrous bear for school, and she's depending on Jim to deliver it when it is ready. When she asks him where the truck is, he says it's still in the shop. But he gets all defensive when she says that she should call to see what is taking them so long on getting the part ordered, so she suspects something is up - she just doesn't know what it is. When she, Dana and Andy are at the market (Dibai Market, presumably named after producer/writer Nastaran Dibai) and she spots Jim's truck, she knows she has him.
After Dana and Cheryl torture Andy into telling them what happened, he gives up Jim. Apparently the other night they were eating wings (5 cent wings!) and this guy was losing at arm wrestling all night. What's worse is he was drunk and obnoxious. When he called Jim "Fred Flinstone" and bet him $20, Jim had to take him on. Naturally, Jim won. Then the guy called Jim a woman and bet him his car against Jim's truck, and, well, Jim lost. When Cheryl heard this, she was furious. So she went down to the bar and got the truck back. She did.
When Jim heard this, he was furious that Cheryl did this to him, and he actually takes the truck back to the bar and gives it to the guy. While you can understand this on one level, for a cheapskate like Jim, it's actually an interesting move. You have to wonder how his mind works sometimes. Apparently it's okay to lose the truck, but it's not okay if your wife then goes down to the bar and demands it back (and gets it back). That's just wrong. I guess he wouldn't have been able to show his face at 5 cent wing night. Perhaps that made it a bad thing. I'm thinking the need to buy a new truck might have made that trade worthwhile.
In any case, the next day, Cheryl asks Jim to take the bear to the girl's school, and of course he has no truck, so he and Andy have to walk it there. When they get into an argument on a hill, the bear heads downhilll on its own and ends up in pieces. Then Jim decides he needs to get the truck back. So he goes back down and challenges the guy and puts up Cheryl's minivan. The only way he will play pool with Jim is if he gets to pick Jim's partner, so Jim agrees, and plays with Cheryl, who is an outstanding pool player. Jim keeps the minivan and gets the truck back.
