Transmission slipping ??
 

Hello I’m new to the forum,

I have a 2004 f150 5.4 4x4. The truck feels normal shifting through gears but when the accelerator is pressed hard to downshift the engine revs up and goes nowhere. Struggles going up a hill also. Changed trans fluid, dropped valve body and checked and everything seems ok. Are the clutches done? No lights on dash.

please any help appreciated

How many miles?

Have the plugs been changed? Any engine lights?

225000 kms. No check engine light. I have not changed the plugs yet. Bought the truck last week with this problem and I am trying to figure out what exactly the problem is.

You may have plugged catalytic converters. Take it to an exhaust shop and have them tested for backpressure.

Thanks for the reply, I never thought of that. I will have them checked.

Restricted exhaust won't cause the transmission to slip, if that is what is actually happening. "engine revs up and goes nowhere" is a poor description of whatever might be happening.

If the engine will rev just fine, you are probably looking at a transmission replace/rebuild.

It was the plugged up catalytic converters !!

I loosened the nuts at the flanges coming off the headers before the cats on both sides to allow the exhaust out and what a difference! She climbs the big hill at the top of my road like a champ gaining speed the whole way. I was actually surprised at how fast the truck was. Thanks glc