Hey all,

I recently installed a new transmission in this truck as it was having issues with pulsing in 4th gear along with hard shifting. Threw a slipping code P1870 and the dealer recommended a new one.

Was driving home from work the other day, and it was having some trouble shifting. Lots of sputtering, hard shifting, and as I hit about 70mph on the interstate, the throttle basically quit working until I dropped to about 55mph. Got home the rest of the way on back roads and it didn't do it again. I replaced the throttle position sensor (after metering the connection to eliminate a PCM issue) over this past weekend, took it for a test drive, and the difference was incredible. Ran like a champ. Looking back, I tested it when it was warmed up as directed from testing so I didn't notice the issue.

The transmission and throttle behave normally when it's warmed up, but the cold weather has been affecting performance. First gear shifts fine, but second gear will stumble and fight until I give it more gas to push it through to 3rd. 3rd shifts into 4th without a problem. Once is warmed up, I haven't noticed any of this in the slightest. Every other vehicle I've owned has been a manual, so I'm not in tune with the normal queues an automatic trans entails, but I'm leaving towards a fuel or spark issue. If I'm in park and rev the engine, it starts misfiring I think around 3000 rpm, but I normally don't drive it that hard. Any feedback would be extremely helpful!