I have a 04 f150 4x4 and recently the transmission i think is slipping for a second when I start moving, I only really notice it when give it a good amount of gas from a dead stop or when i start out going up hill. So my question is has anyone else experienced this problem. It only has 49000 on but im planning on doing a transmission flus the next time i have a chance and replace all the filters and oil.

 

Would you be experiencing the driveline clunk from takeoff? I experienced the same thing and turned out for one, my output shaft seal broke, leaking out the fluid and drying the splines, and secondly, my rear differential seal was leaking. Dealer replace the seal, re-lubbed the splines (no shavings were present) and re-filled/re-sealed the rear differential. Problem solved.

Going up the hill issue is most likely torque converter lockup, I experienced the exact same thing. Dealers of course call it normal. What fixed this for me was a new set of Troyer Tunes!

 

Thanks for the info.
Where is the output shaft seal. I having noticed any leaks, but considering that the parking lot im at has oil stains all over it it will be hard to tell.
Thanks

 

the output shaft is the part where the driveshaft enters the rear of the transmission. if it's leaking, it's very noticeable. the red fluid is somewhat hard to miss (trust me, been there, done that)

but yep, sounds like your driveshaft is causing the clunking. you may also need new u-joints in addition to checking the other stuff

with the truck parked, crawl underneath and try to move the driveshaft. it shouldn't move. if there is slop, it means the u-joints are bad.

 

Alright I found the culprit.
My rear differential seal is leaking in the upper left hand corner. So i guess its time to take advantage of the nice sunday and replace it. Might even put royal purple into it.

 

Glad you found the culprit! From what I understand on these trucks, leaky rear diff seals are not uncommon.

 

I might have spoke to soon. As I left my parking lot and went up the hill I noticed the shutter again. Like I said earlier I noticed the real differential seal had blown in two small spots in each of the top corners. Pulled the covers off and the oil looked like ****. It had a lot sludge in it, well not to bad just worst than what it thought it should look like for a truck that has been well taken care of with only 49 k. So i spent almost my whole afternoon cleaning and replaced with Mobil 1 synthetic oil. I also checked the drive shaft and it was solid with no play. Checked the trans oil, at normal level and still nice and bright red.