Four wheel drive not working properly

ANTHONYYOUNG

MEMBER
2008 FORD F-150
4.6L
V8
4WD
AUTOMATIC
212,000 MILES

I was trying to take truck out of 4x4 while parked in a parking lot, would not come out of 4x4, so started driving and got 300 feet and heard a loud bang, truck made a big jerk and now it only moves at 5-10 km/h, but speed hand and RPMs still go up. What could this issue be? Truck has 212,000 km not miles.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,705 POSTS

Is it in low loc? When you say the speedometer and tachometer still go up, either something broke and isn't engaging the transmission to the wheels or you are in low 4wd gear.

If possible, record what it's doing and upload it for me to see.

I will watch for your reply.

Joe

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Sunday, March 20th, 2022 AT 8:44 PM

ANTHONYYOUNG

MEMBER
2 POSTS

I’m aware something is not working, that’s what I’m trying to figure out what’s not working, and no it was not in 4 low, it was in 4 high, it has a switch for 4x4. I switched back to 4 high and started to drive again when it made the bang and jerk. Now when I press the gas the engine revs up normal, the speed hand goes up, the RPM hand goes up, but the truck itself is doing about 5-10 km/h.

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Sunday, March 20th, 2022 AT 10:09 PM

JACOBANDNICKOLAS

MECHANIC
109,705 POSTS

Okay, if the speedometer is going up, that tells me the internals of the transmission are working. An educated guess is the direct clutch in the rear of the transmission has failed. The sensor would still pick up the output shaft speed, but the vehicle wouldn't want to move.

So, rather than having a broken output shaft (because it still moves), I suspect one of the snap rings has left loose resulting in the clutch pack not being able to fully engage. Basically, the friction plates and steel plates in the hub are loose and unable to engage.

Keep in mind, I am not there. This is a theory based on movement and the speedo showing the speed increase when the vehicle really isn't.

Let me know if this helps. I attached two pics below showing the components in question.

Take care,

Joe

See pics below. Keep in mind the clutch hub itself may have broken as well.

Images (Click to make bigger)