Strange 5r55e issue...

[FordSHO8991]

I have looked on the forum several times for an answer to my (apparently unique) problem. I have a 1999 Explorer Sport 4x4 SOHC with the infamous 5R55E. It has the tow prep package (4.10 gearing, transmission cooler). The problem is this: I'll be driving and the o/d light will flash (I know this is a common issue). But what it does during this is uncommon: It will shift fine, overdrive works, but torque converter will not lock up unless I restart truck, then the problem goes away. It happens once or twice a day. It does not happen on highways, only around town and depending on terrain. If it's hilly/mountainous (as out in central/western massachusetts for example) it will do it more often (during my day trip out there it did this 7 times! talk about frustrating). It does not correlete to outside temp, it does it when it's warm or cool out. I have replaced several parts to no avail. I worked at a ford dealer until recently, so I had the pan dropped and the following was done: seperator plate replaced, valve body gasket replaced, valve body rebuilt, torque converter clutch solenoid replaced, and fluid and filter change. I also replaced the idle air control valve, and throttle position sensor. No other issues with the truck, it's in way above average shape, and only has 115K. I have owned it for 6 months and 4k miles and it has always done this; it isn't a new issue. All new parts were motorcraft units. Input from anyone is greatly appreciated; I'd like to try to solve this before it could turn into needing the transmission rebuilt or some other expensive fix.

-Kenyon

 

[JK080]

A flashing OD light tells you that there is a code stored in the computer, get this code or codes, this is the first step in diagnosing a transmission problem.

 

[FordSHO8991]

Oh thank you for bringing that up, there are also zero codes coming up. I know you need a proper (expensive) scan tool and the transmission tech at the dealership was baffled by no codes showing.

 

[PopRichie77]

The torque converter not locking is the problem, it's possible that the torque converter is bad but more likely that there is to much internal seal fluid leakage, resulting in not enough pressure at the torque converter regulating valve to open it sometimes, the problem will get worse, it might take another 10k miles until the converter won't lock at all. I would say that a rebuild of all seals is needed.

 

[FordSHO8991]

Thanks for the info poprichie, much appreciated. I'm guessing if all the seals should get replaced, I might as well rebuild the whole unit?

 

[2000StreetRod]

BOO Switch, ECT sensor & TPS?

Make sure that your Brake On/Off (BOO) Switch is not sticking in the brake on position or shorting. The PCM may release the TCC when brakes are applied.

Also check the operation of the engine coolant temperature (ECT) sensor. The ECT sensor is used to control TCC solenoid operation.

Test the TPS. The PCM uses the TPS output to control TCC operation.

Does the PCM go into and stay in closed loop? I recall reading that the torque converter will not lock when the PCM is in open loop.

 

[FordSHO8991]

Streetrod, it looks like I have some checking to do tomorrow! I did replace the tps but I will test anyways. I'll post my results tomorrow.

 

[FordSHO8991]

Streetrod, I checked the boo and it appears fine (I will borrow my dad's voltmeter tomorrow for the electronics end, I don't have one at my apartment). After doing some research I have a feeling the ect may be part of the problem. I am also getting really poor fuel mileage, the truck will use a quarter tank every 40-45 miles. Some quick math makes that....10.4 mpg . Thats with new plugs wires air/fuel filters and the IAC. But thats straying a little off topic for this forum. If only my contour svt's clutch wasn't on its last legs...

 

[PopRichie77]

I assumed before that you had a properly running engine. The engine has to be running properly for the PCM to operate the trans correctly. Also a dirty or bad MAF can cause bad mileage and also cause trans problems.

 

[FordSHO8991]

As far as running goes, it runs good, no rough idle or anything of that sort...just bad fuel mileage. Also intake gaskets were just done as well. Unfortunately I couldn't diagnose any further because now my girlfriends 96 4.0 wouldn't start (cranks won't start does this only occasionally) so I need to diagnose that first since she has a job and I don't.