trans slipping?

[KevinZwick]

I have had no luck finding this on the site!

When I am driving over 50mph, and I stomp the gas, the transmission hesitates once, I hear a loud hiss sound for less than a second, and then the trans engages 3rd gear and goes. The more weight I have (The bigger the load on the engine), the longer it hesitates before engaging.

I first assumed a misfire. So I changed the plugs, wires, and the coil pack. That did not solve the issue.

Next was my differential. It does have the hipoid whine at highway speeds, but I asked a master ford tech at work and he said I would not feel any kind of slip from that.

Then I started thinking about the hiss that I hear. It sounds like a blow off valve on my transmission. I was thinking the vent tube on the transmission (I dont know what it does or how it works). I looked under the truck and I can find nowhere that fluid is coming out of the vent tube. I recently had the trans fluid flushed at the dealership where I work and asked the tech who done it if it was possible that he overfilled or underfilled the transmission. His reply was that it is impossible to overfill this particular transmission with the flush machine he used. And I was the one that sold him the fluid so I know he put enough in.

I need help with this issue!
I'm pretty sure it started when I flushed the transmission.
Is anyone else having this issue?

 

[swetrid]

The flushing equipment is not perfect so i would double ck the fluid level.

 

[KevinZwick]

I checked the fluid level myself at temp. Fluid level is good. I also had the pcm reflashed today to eliminate the possibility of it relearning the habit, or to unlock the relearning system (which i hear may happen).

I still have the symptom.
I found today in a ford service manual that a clutch seal or check ball leaking may cause a hiss sound in the 5r55s and a few other transmissions.

(edit) I misread the service manual. That hiss occurs during pressure testing, not during operating conditions.

 

[LoKo498]

How do we check the fluid level on our trans? I can't find a dipstick.
I also have a trans slipping feeling when I drive.
Not sure if I should get a trans flush or what I should do yet.

 

[armysoldier30263]

look under the truck ... see the drain plug on the tranny pan? see the allen head on the inside of the drain plug? unscrew that and if fluid comes out your good if not it needs some fluid ... DO NOT UNSCREW THE BOLT you will drain the pan ... i also let some fluid out and used the lucas trans conditioner and it helped a little bit ... hope this helps