Stock truck bought new, 225000 miles now, have had the P0871 code randomly pop up.
The truck has been made lighter and running stock tunes for three months.
Most of the miles are Hwy, and most have been towing.
Yesterday I noticed it was shifting strange; it almost seemed to change within the same gear.
Then I had to haul my dump trailer loaded fully.
I heard it slip of few times, then hard shift and lock in gear.
I stopped and cleared the code and would do the same thing again.
I parked the trailer and returned today to get it using the manual shift.
I got the P0735 in 5th and could see 5th slipping.
I would not go into 6th.
Even now unloaded, I can feel it fluctuate in 5 and 6th.
Earlier this week, I was in the mountains and noticed it was downshifting more but just thought it was the area.
Any ideas, or is it time to upgrade?
Bookmarks