4x4 stuck causing drastic MPG loss

As others have mentioned I doubt it was in 4wd unless no offense you're that oblivious. Even if your indicator failed to light up, turning, daily driving, etc. in 4wd would have been VERY EVIDENT something was wrong.

 

I think the point he's trying to get across is that 4wd was "partially" engaged but not completely, although I'm not exactly sure what that means and how it would equate to terrible MPG's.

 

If one wheel or the system had not fully disengaged you might not notice it. The indicator light was not on. Plus keep in mind I was having several other issues including low fluid and the TSB so it wasnt running correctly to begin with

 

I disagree to an extent. If youre in 4hi and mostly driving in slow traffic with wide radius turns, stock truck, new to the truck, you might not notice. Either way once you try and pull into a parking stall youll feel it.

 

Ok, so all of you who are saying that I would notice if I was in 4hi/4low... thats not the point Im making. The truck was sending power to the front wheels robbing me of MPG. It would try to engage randomly with the truck was under extreme flex/stress. The pics I posted where before and after playing with the 4x4 system and there is a dramatic dif in MPG... from 12/13 to 21/22. it was night and day. I have seen other with similar mileage and wanted to show I had a simple fix that could be the culprit. Not sure what the issue is with my 4x4 tcase or why it would cause the mileage to drop. but it did and its been better ever since.

 

So you're suggesting that power was being sent to the front, but the front wheels did not "receive" it? The transfer case is either engaged or not, there's no middle ground for the kind of magic scenario you're envisioning.

 

as 0210 saidd..... you are either in 2wd, 4hi or 4lo. if its stuck in 4wd then i think it would be in 4wd. theres no half and halld. if it was partially engages you would hear grinding, gears skipping etc.
if the front wheels were locked or stuck in 4wd then you would have been in 4wd.

not arguying just stating that a transfer case is either engaged or not engaged.

 

.....

 

If that's the case, I'd imagine the teeth on the brass synchro are shot.

 

@ 8:00 minutes

 

That's your issue right there, at night you get 12/13 mpg, and day you get 21/22 mpg. Sounds like your truck doesn't like the dark, thus uses more gas then. (Sorry couldn't help it).

So from what I understand, if the wheels aren't engaged your not using energy to drive them. The question I have is it possible for keep engaging and unengaging? I would think that would be felt/noticed.

 

In the 2nd picture you posted the Trip Distance is 2.9 miles. At that distance, you are almost always accelerating which is what gives you bad mileage. 2.9 miles is not nearly enough of a sample size to gauge what your truck is getting. The picture you posted with around 21 MPG, you also drove for about 22 miles.

 

Correct.

Put it in 4 high now and briefly drive it, on dry pavement, including one tight turn. Then you'll understand what you were missing before.

4wd being 'partially' engaged is like being partially pregnant.

 

Doesn't the 4x4 indicator flash if it is not fully engaged? Also (don't want to assume) but if you have ever driven a 4x4 with an electronically controlled transfer case, it is actually pretty easy to tell if it is fully engaged versus not. Also, wouldn't a test drive before you took delivery present this issue before having to drive X amount of miles? Glad you got it worked out, just curious about more details.

 

A buddy of mine bought a brand new F-150 FX4 a few years ago turned around threw a 6" lift and new wheels and tires. After he got it back he complained for about a month that truck was driving like crap. He took it to the dealership and the service guy hopped in drove out the lot and realize he had been in 4wd for over a month. Still blows my mind that he couldn't figure that out or noticed the light.

 

I have I'm not that dumb. Shows a page of tank and currrent fuel Econ, trip and time, then a blank page.

 

The trip details like that only show when you turn the truck off and do not open the doors. Weird, I know.

 

He's not necessarily in 4WD at the transfer case, but if the sliding sleeve in the A.D.D. isn't disengaging the front end would still be spinning and that would kill your mileage. As the OP says, it would be the same as driving around with your manual hubs locked. It's a lot of mass to spin. Removing the hubs and using that vacuum actuator has been a pain in the ass since 1990 when Toyota first started using it. What's wrong with a danged transfer case lever and locking hubs anyway?

 

As mentioned above, the display in the op is when you first turn the truck off and haven't opened the doors. However, you can customize what is displayed on the normal screen.