Hey guys, first post here. I'm usually more active in the Powerstroke forums, since my half ton has been spectacular.

Bit of backstory. 2005 5.4, 4wd, currently approaching 240K miles. Like I said, it's been a fantastic truck. I did plugs and coils when I bought it 60K miles ago, and everything else was preventative maintenance until 200K miles, when the original transmission went out all at once. Pulled into a parking spot and it was fine, pulling out and every gear slipped like crazy. Can't fault it for that, it's been worked hard and any automatic transmission that makes it to 200k with lots of heavy towing is OK in my book. I work in the salvage industry, and know just about every junkyard owner in the state, so I got a great deal on a low mileage (90K) used transmission that I swapped in, and it's been good until tonight.

Went to pass someone on the highway, and with my foot to the floor at about 40 the truck downshifted to second as you'd expect. Shifted into third pretty hard, but not hard enough to cause tremendous concern. Fourth and overdrive were fine as always. 20 miles later, the trans fault light came on with the standard flashing overdrive light. Pulled the codes on my edge (running stock tune, I just use it as a monitor), got P0731 and P0732 for incorrect ratios in first and second. Truck was driving fine, so I kept it moving. Came to a stop sign, pulled out, and the truck had no power. Again, foot to the floor and it wasn't slipping, just accelerating like I was barely giving it any gas. After about 15 it caught and actually broke the tires loose, and I made it home.

Some experimentation has revealed that with the gear selector in reverse, 1st, and 2nd, it might as well be in park. On a grade with the nose pointed up a hill, it will roll backwards in neutral, the torque converter holds it steady in drive, but anything else and the transmission is completely locked, and you can rev the motor all day long with no impact on what the transmission does. Shut the truck off and tried driving it again and now it won't shift into overdrive. I can hear and feel something moving in the transmission when shifting into reverse, and in park and neutral I can hear a RPM dependent whine from the transmission. Added a quart of transmission fluid just for S&G's, no difference.

I consider myself very mechanically competent, but automatic transmissions are black magic witchcraft to me. In my experience though, things don't fail in this manner. I'm trying to reason my way through what could cause reverse and a manual selection of 1 and 2 to lock things up but in drive it at least moves, and the fact that it doesn't slip in drive but won't increase engine speed until it grabs strikes me as odd. I read a post from a while back about someone who had the lock for the reverse gear clutches fail with very similar symptoms a while back, but I don't know enough about autos to know if that sounds reasonable.

Any advice would be welcomed. I really don't want to put another transmission in the truck with this kind of mileage, but my other vehicles are in even worse shape, so I'm going to have to make a decision eventually. Thanks in advance!

 

I've never heard of a lock for a reverse gear clutch. It sounds like a part that someone who knows nothing about transmissions made up. That's the problem with internet diagnosis. A good writer can make it sound like they know what they are talking about.

I think you're going to have to do what you don't want to do. The reverse clutch is sticking on. Usually, that happens because the clutch was overheated and warped and can no longer release correctly.

 

An update for those interested. I spent more time today playing with the selector, in first gear it might as well have been in park. No movement, not responsive to throttle input. Second I found would creep a little bit as the tachometer climbed, so I did what any self-respecting truck owner would do and pinned it. Transmission clunked, the tires spun, and now I'm back to having a fully functional transmission.

Obviously something is broken, and eventually the issue will come back, but this gives me hope that it's something that can be repaired rather than replacing the whole transmission. Shift solenoids maybe?

 

It's not the shift solenoids. It is something mechanical inside the transmission.

 

Okay, so what can fail mechanically that would cause a transmission to lock into third and fourth gear and then spontaneously fix itself?

 

The reverse clutch was stuck on. You broke it loose, but chances are it's going to stick again. They usually stick when the clutch is overheated, which causes it to warp.

 

That sorta makes sense if I start making educated guesses about how the rest of the transmission works. So what causes the reverse clutch to warp? Seems like an odd thing to have go.

 

And why would the reverse clutch decide to freeze when doing 55 on the highway?

Not trying to argue with you, trying to understand how it works.

 

Possibly internal leakage put enough pressure to the reverse clutch to make it partially apply. This would allow it to slip which will build heat FAST. That will warp the clutch.

 

I had an audible chuckle when I read about the 90K mile transmission you installed. My '07 transmission failed at 92K. Broke as in needed to be replaced. It now has a Jasper remanufactured transmission with a forged front drum. Breaking at the snap ring groove is a common failure point. When you are in O/D and you jump on the throttle into Third or Second, the "bang" of the shift puts extra stresses on this groove. (according to PATC)

The part is $175, not bad. If you ever have this transmission apart replace the front drum even if you don't need to.

You gotta love those Ford automatic transmissions!

 

The 4R75E is supposed to be filled for life. They told me that when I bought it.

 

Never believe anyone when they tell you something is a "lifetime fluid".

 

Yeah, I hope Ludwig van Beethoven was being facetious.

R.