Had to have Tranny re-built.

[F150 Man 4Eva]

Well I put the rebuilt tranny through a pretty tough test last weekend. I was towing my 7,200lbs boat and trailer with 60gal of fuel and a full tank in the truck...4 passengers all with luggage...about 150 beverages and 100lbs ice. I estimate I was towing near 9,000 lbs. in total. Keep in mind I have 35" Nittos that weigh near 80lbs. ea. as well. It was about a 50 mile trip going 70mph pretty much the whole way. The King Ranch was struggling I must say. It was tough to keep 70. The SLIGHTEST incline, if I tried to maintain speed, it would down shift to 2nd with the TC locked, and pretty much stay right there until I let off the gas. The tranny never shifted to 4th....it wanted to stay in 3rd with the TC locked, most of the time. I had the O/D off in custom tow mode. My tranny has been staying around 150 degrees under no load. I just pulled a 5x10 trailer with a golf cart...and it was more like 160. Well with the boat and all..it varied a good bit. I believe it was mostly around 180...but at one point (when it down shifted to 2nd) I saw like 201 or 202 just for a moment. That made me uneasy....I was NOT comfortable running that hot on my patched up tranny. I did see 190's and high 180's a good deal. But like I said, MOSTLY..it was around 180. Is that normal? At what temp. will the fluid become burnt?