Comment by I_Am_Nous

This reminds me of an old F250 my dad had. He towed it from Colorado to Missouri and about halfway he noticed his gas mileage got worse. But, you know, coasting down mountains until you get to plains would also have a similar outcome, so he didn't think about it.

Once he got to Missouri he noticed the transfer case (I think) had somehow bounced out of neutral and was partially engaged, which chewed many teeth off the flywheel. To start it we had to get a pipe wrench and manually rotate the flywheel to a spot with enough teeth to catch the starter and turn over. That got harder and harder (as it kept chewing off more teeth) so eventually we had to push start it and pop the clutch. Thankfully it was a manual so it still worked!