Fixed the truck, but somethings not right
Get a cold one, this one could be a long one.
First a refresher. I have a 2005 F350 XLT 4x4 Dually. I couldn't get anything better than 7 or 8 MPG. Truck was tossing the wrench light when towing, especially uphill and when it was really hot out. Dealer was useless, said the truck was fine. I said BS. The wrench light never set a code, so never knew what was causing that. I've been living with this for about a year. Diesel prices hit over $4.50 and I said I had to do something. I wasn't giving up camping that easily.
I decided to start throwing parts at it.
Yanked the air filter (found out it was the original one, 95,000 miles on it).
Yanked the muffler and replaced it with a Walker BTM.
Guess what. Pulling 7500 pounds of trailer and the mileage is up to 11 MPG. These are all hand calculated MPG's.
Just got back from 2 camping trips and no wrench lights either.
You may ask what could still be wrong. Well, it feels strange. Like it's congested. Like it has a head cold. I checked the air filter, it's in correctly.
I can hear the turbo exercising itself when I first start the truck up. Couldn't do that with the stock muffler.
I don't know what it could be. Did the truck lose power with the muffler replacement?
I also noticed that with the new air filter and muffler the truck isn't down shifting on hills as much as it did. The boost goes up to 20 or a bit more, the speed will hold or drop a bit but there is no downshift unless it's a really big or long hill. Seems like the truck is boosting more and downshifting less.
Here's a fix that I can't believe but it seems to have done something. I noticed that my third brake light was out. At the same time I read in an RV forum that if it's out the transmission will not shift correctly and you may have cruise control problems. Anyone ever hear of this one? My tow haul mode is working better and the cruise is holding better after replacing the third brake light bulb.
Any ideas? I'm happy with 11 MPG but a bit concerned if I'm losing power with the new muffler. Maybe the cats plugged?
Thanks for reading