2002 F-150...4R70W transmission...

So I just went through changing out the transmission fluid and filter in my truck. I refilled the tranny pan until the level was in the 'cold' on the dipstick. Then I went to start the truck, everything sounded fine. Once I shifted into 'R', there was a 'hissing' sound...'N' it went away...'D' it came back and was still there through 2 and 1 gears. Shifted back up, it stayed until I hit 'N' again when it went away, then came back shifting into 'R'...and went away when in 'P'.

I don't have anyone here to go through the gears while I got a closer listen, but any of you knowledgeable people have any ideas as to what may be causing this? Could it have anything to do with the filter? Kinda sounds like a vacuum hose, although to my knowledge I wouldn't have taken any of those off...unless inadvertent.

Thank everyone for the input.

 

With the trans warmed up and the engine idling in park, where is the fluid level?

 

Chris, how much fluid did you drain from the transmission?
You must remember the transmission runs on nearly 23 quarts of fluid.
If only the pan was full, putting the trans in drive or reverse sucks the pan dry or below the pickup screen.
The front pump does this trying to fill the converter where most of it ends up.
When you shift to drive or any gear, the computer opens the electric pressure control solenoid to allow the pump to move fluid into the valve body.
What did you do?
Good luck.

 

Actually the 4R70W uses 14 quarts.

Fluid is moving into the valve body any time the engine is running. The pump is ALWAYS supplying the valve body.

The Electronic Pressure Control (EPC) solenoid controls the main regulator valve, which controls line pressure. No matter what the EPC does there is still fluid flowing to the valve body.

 

Gentlemen...thank you for your replies, sorry it took so long to get back on here.

Mark, to answer your question, after the transmission was warmed up I was reading a low level on the dipstick...where it says add. Unfortunately I was doing this in 2 stages...drain the pan, reinstall pan, add 5-ish qts of fluid, start truck for 30-45 sec, drain pan again, reinstall...then add until it registered in the cold area of the dipstick. So the initial reading I wasn't too concerned about because I was going to drain it again.

After the second re-install and adding of fluid is when I heard the noise. I let it idle for a bit, shifting through the gears. When I got it up to temp, I checked the dipstick level and it was still in the 'cold' area. I added another 1/2 quart and checked again. It was then at the top end of the 'hot' area. The sound was a little quieter, so I took it out for a slow drive and it eventually went away. I checked the level when I got back home, and it was still at the top end of the 'hot' area, and the sound had subsided.

Seems to be running the way it was prior to the fluid replacement. I will keep an eye on the fluid level for the next couple days, but everything seems to be checking out alright.

Thanks again!!