Ford F-150 (2009-2014) :: 2010 - Transmission Starting To Slip

2010 STX with 4 speed (4r75E)... Yesterday morning when I was almost at work(20 minute drive) I went to accelerate from a stop sign and my truck acted like it was in neutral. Once the rpm's dropped to just above idle speed the transmission caught and I was able to accelerate as normal. I guess I didn't think much of it until I was coming home from work, again about 20 minutes of driving, when I was accelerating while turning left from a stop sign. Halfway through the turn my rpm's shot up to about 5000 and it was acting as if I were in neutral again. Just as before, when the rpms dropped to just above idle, the transmission reengaged and everything was normal.

I decided to take my wife's van to Walmart and grabbed a bottle of lucas oil "transmission fix". I figured it might buy me a little time before I am able to get it to a shop for diagnosis. I used a suction pump to remove approx. 24 oz. of tranny fluid through the dipstick tube. I then added the lucas oil "tranny fix" (24 oz. bottle). I inspected the fluid that I removed. It looks pretty dirty. I would say that it was a nontransparent brown color with a slight red tint. when poured onto a paper towel it still looked brown. It didn't smell burnt at all. I checked the fluid level twice before I added the lucas oil, and twice after. Both times the fluid level was at the full mark (fluid at normal operating temp, with vehicle in park after shifting through all gears).

Fast forward to today and I was able to drive from my current house to my new house(being built) which was about 10 minutes away. I had no issues at all with the transmission. after being at the new house for about an hour and a half I came back home with no issues. about 30 minutes after returning home I headed back out again to run some errands. About 15 minutes into the drive my transmission slipped again as I was making a right turn into the barber's shop parking lot. after about an hour at the barber shop I headed for home again. As before everything was fine for about the first 15 minutes until I tried to make a right turn after sitting at a red light. the transmission slipped as described before, but it did it twice this time in the same turn. Nothing happened after that within the last 5 minutes of driving home.

The slipping only seems to happen when accelerating from a dead stop or from an extremely slow speed(under 5 mph). At highway speeds the transmission down shifts and upshifts just like it always has. My truck has 78,800 miles on it and has never shown any previous signs of transmission issues other than a leaky dipstick tube that I replaced about 3 years ago.

My father had a 94 Taurus that had similar symptoms in the past and it ended up needing new clutch disks and was rebuilt. I'm hoping for that rather than a new or reman'd tranny!