P0700 just means that the trans computer has set a code. You need to have the trans computer checked for codes. When the trans sets a code it defaults to safe mode, which is 2nd gear only.
NO!...overdrive is for highway driving, with an empty truck, not towing anything, 55mph plus. Straight from the mouth of General Motors my friend!
6 hours?
275 miles.
400 ft
385 miles.
they reduced it to 55mph
31 minutes 38.18 seconds.
4*55 = 220 miles
6 hour 10mins approx.
Little braking, gradual starts, no hard pressure on either pedal, non-stop driving, driving between 45-55mph.
You may have a rear tire out of balance.
a fouled fuel filter will do that. that'd be the first place i'd start.