On the bright side, things could be worse, wife leaving you with the kids for instance, then $3800 might not have fixed the problem, but at least it's money she won't get, lol.
Do you maintain it regularly at the dealer, or another shop? If not that might be your problem. You run it until things break, and cost you money instead of someone catching a problem before a part breaks completely and costs you four times the amount it would have in the first place. If the truck tows heavily, gets abused off road, etc, then parts will fail. Buying cheap fuel? Thought so.
Any older vehicle after a few years will start to cost money to keep it on the road. True, some vehicles will cost more than others in terms of wear and tear parts. One year I might luck out and not have any problems with my Dodge for instance, and this year so far I need a new steering rack (so I think at least, it's going in on Tuesday to get checked), and a tune up, coolant change and transmission service.
So it'll cost me about $1500 with labour for everything but for what I use it for, that's not bad. Diesels are more complex, cost more up front, and cost more to maintain. If you bought it for mileage, that's fine, but in the end it's still a diesel. I prefer diesels myself, but I don't need to tow 10K regularly, so it doesn't suit me. I buy my vehicles for a purpose, not to worry about maintenance costs or fuel economy. Spending a few extra bucks ahead of time can save you hundreds down the road.
Best thing is that my vehicles are maintained exquisitely enough that I can get into my Durango, Taurus or G6 and drive to Texas and back from Ontario without worry of mechanical problems. Now, that's not to say nothing will go wrong as all my vehicles are man made and can have problems unexpectedly. I don't mean to rant but I just had to say it, for when someone complains about maintenance costs and they point the finger at everyone but themselves ... well anyway.
Don't feel compelled to buy new parts all the time either. Shop around online at RockAuto Auto Parts
for instance, and you can find close to new parts for 1/4 the cost of buying new at dealer prices. You can also contact Ford directly if you consider it to be a problem they should be aware of. I don't think they'll contact you about it as the truck is 5 years old, perhaps 6, depending if it was made in late '04.
If I had to drop $4K on my Durango, when it's only worth $4K, I might consider trading it in, but for now, it works great for what I need it for.