I know that some take pleasure in knowing they worked the system to their advantage, but at what total cost? BUT you need to know the field you are playing on, which can change. DO your research and see what the book values might be on your truck on the online price guides. Then deduct for any wear/tear/dents/dings. Might even do a Carmax (or similar) bid, too, or even take it to a dealer to check for trade-in (at Ford or GM dealers). Various sources, in other words. What the dealers might bid would very possibly reflect what your local market is doing, which the online services would not. Did you just float for bids on the new truck without any potential trade-in in the mix?
THEN, how much of your time do you desire to devote to selling the vehicle? Especially if it might take away from your (hopefully) productive working time? What's YOUR time worth? Might any potential buyer be in a similar business as yours, who might need what you have? OR will it be "general public"? In other words, consider your potential buyer and their capabilities to get financing on your vehicle. Some might perceive they can do more than what their banker(s) will let them, by observation. Can't forget the tire kickers, who would be doing the same thing to you that you might be doing to the dealers.
I'm not your and you're not me, nor are we in the same part of the country. But to me, do the trade-in deal, pressing the dealer for his "best deal", but still allowing them the possibility to make money on the complete deal, at the same time. If they are selling the truck at a deeper discount in order to keep their sales allocations, you can milk that deal a bit, I suspect, in the trade-in value.
But to me, I don't really like the drama of selling a used vehicle, myself. I'd much rather get the best deal that I was comfortable with, let them make a bit on the trade-in, and go on down the road with a vehicle I wanted with NO worries about trying to get rid of the used vehicle. Getting on with my hopefully-productive life at the same time.
Everything's got a cost. Whether it be your time in selling the used vehicle. Paying a bit more in the total deal with the dealer getting the trade-in.
ONE thing that a business person might consider is "How much of the used truck's value has been depreciated for tax purposes?" Possible "gain on sale" might end up costing more on taxes?
Some thoughts,
CBODY67