you should have a button on the end of your shift knob (tow haul)- put the transmission in D and push the button- you should see an amber tow haul sign on the dash- then you are good to go- it won't go into OD unless it is safe, but MAKE SURE you push the button in and turn it on. I hope this helps.
If you are hauling in the mountain, put it in 3rd gear with tow/haul on. Anywhere else, D with tow/haul youre fine.
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