My 2001 f150 4x4 with a 4r70w start slaming hard. Once at speed in overdrive it ran fine. Then driving around 25 it would be fine for a minute or so then I could feel it binding up then a hard slam. Then it would drive fine for a minute and do it again. Mechanical? Electronic? Torque converter? Any input is appreciated. Thank you

 

Not sure if your description describes what I had with my 2001 S-crew. But I had a significant thunk at times and sometimes a shudder. It did throw the code for the TCC solenoid (have you checked for codes?). I pulled the pan and found the yellow plug in there. 180K and the tranny fluid had not been changed. I changed the fluid, replaced the TCC solenoid and all is well now. Acts like a new truck now.

 

Yeah it's how many of these trucks you see with 150k+ miles with original fluid/filter, when its supposed to be changed every 30k

 

I haven't checked the codes. The truck is 100 mile from anywhere. It won't drive any now. It go's into gear but slams hard and the whole truck jumps

 

It's my parents truck. They had the trans flushed a few hundred miles before this. Wrong fluid possibly?

 

Maybe the transfer case? Did you try running through the gears in 4 low?

 

I tried all ranges and manually shifting to first. All the same result. In reverse as well

 

I'm leaning towards the transfer case,sounds mechanical

 

Agreed, i was thinking transfer or rear end.
Jack up the rear so both tires are off the ground(block the fronts), support good, spin the rear tires by hand(in 2wd), bring a buddy if you can so he can spin while you listen.

 

If the EMG brakes have never been looked at, good chance one side has come apart.
The linning peices can jamb up and parts move all over inside because they have no place to go.
Can feel like someone hit the truck with a sedge hammer.
Good luck.

 

Ok. I drove 3 hours to where the truck is. Thank god for satellite internet. Anyway, when I lift the rear axle and turn the wheels nothing sounds off. But the driveshaft only turns when I rotate the wheel in one direction. Is this normal? Shouldn't the drive shaft turn any time the wheels do? I'm new to workong on drivetrains, but I have no choice do to the lack of almost $1000 to tow it home. Thanks in advance for any help you can give.

 

What you need to consider is; is the rear open or traction lock?
If open and one wheel is frozen or very hard to turn only one wheel will rotate with the drive shaft.
If traction lock both wheels wants to turn along with the drive shaft.
What do you have and which way does it act?
Example if the rear is an open type and one wheel is jambed, the other will still turn as long as the transmission is in neutral.
Example if the rear is a lock type and one wheel is jambed the other would be very hard to turn against the internal clutches unless you used a long Tee bar to overcome the torque needed to make the clutch slip.
At this point you need to revisit the rear to be sure what you have, good or bad.
Good luck.

 

I don't know. Open I think. Its a 2001 super crew 4x4. With a 3.55 ratio and 9.75 gear. I don't know much about how the drive train actually works but I can tear it out and put it back easy enough. Just trying to figure out what needs replaced when it isn't clear what's broken that's the problem. When lifted all wheels turn freely. But the rear only turns the shaft in one direction and not the other. The front turns the shaft in either direction but not the other wheel. I opened up the rear end and it's like new inside. Going to start draining the other components in the morning and try to diagnose it that way. As hard as it was slaming and as much noise as it made metal shavings are bound to pour out of somewhere.

 

Wow what a way to work!
If you had the cover off the rear already and don't see anything obvious but the drive shaft won't turn in both directions, consider the EMG brake issue I discribed.
It's not the transmission doing the one way thing.
EMG brake lining laying in the bottom of a rear drum can 'wedge' in one direction, catch intermittantly etc. Those parts can't get out of the space.
If the discs have never been off, you will have quite a time getting the discs off without heating the enter area with a torch after removing the brake calipers.
Look at the door jamb sticker for the axle equippage open or lock type..
One thing I can tell you is, if your sure the rear is a 9.75, the motor is a 5.4L not that it help in this case..
Good luck.

 

Brakes are good. A pile of metal in the trans pan tho.:-/ but the way in was acting I think the transfer case locked up and shredded the softer parts in the trans. Oh well. Much work to do. Thanks for your input.