TCC Problem

[sundownff]

Hey Everyone,

This is my first post, but I've been searching through this forum for weeks now and ya'll have some great info here. I think I have my problem pinned down but I'd like a second opinion and possibly someone to jog my mind so I know I have covered all my bases.

I traded my 1990 Jeep Cherokee for a 1999 Ford Explorer SOHC with 152,000 miles. It was sort of a gift horse trade so I didn't look it in the mouth so to speak. I figured I could fix all the possible problems that could arise. That was until the O/D light started flashing at me a few days later lol. I've rebuilt manual transmissions but I have never messed with an auto. Unfornately no one in town will touch it so I've been forced to do this one on my own... no biggy, do my homework and talk to ya'll a little and I should be able to fix it.

At 70 MPH, my RPMs are around 2200. Apparently this is normal for a 5R55E in my configuration. I can cruise down the highway with no problems until i encounter hills or excessive speed. After the torque converter clutch dissengages three times in these conditions, the O/D light starts flashing until the key is turned off and back on. No codes are being stored and yes I have checked with a professional diagnostic computer. After the light starts flashing, the TCC is deactivated and RPMs stay around 2700 RPM at 70. By pressing the OD button, I can further increase the RPMs to 3200 so I know it's the TCC and not overdrive.

Possible Problems (please add/subtract if I'm missing something)
1) mechanical issue with TCC
2) blown out seperator plate
3) TCC solenoid
4) plugged cooler line ???

I am assuming the problem is not electronic in nature. Everything else shifts fine and anyone driving around town would never detect a problem. I have preformed the 1st gear test by driving about 20 MPH and manualy shifting to first. In my F150 with a hydraulically operated AOD, this downshift and engine braking would be rather drastic and apparent. I am not noticing much slow down in the 5R55E. It seems to me like this points to a bad seperator plate, but I am not sure what normal should be like.

I have run sea foam through the transmission for about 200 miles and dropped the pan and changed the filter along with about 6 quarts of fluid and a quart of Lucas Stop Slip. I noticed a slight improvement in how much load the TCC can take before deactivating but that could also be my driving habits adjusting to compensate. I am leaning towards a seperator plate so I have ordered a new bonded seperator plate from Ford part number 1L5Z-7Z490-HA for $34.22 before tax. I also went ahead and ordered a new TCC solenoid from AutoZone, part number 56843A Dacco brand for $94.99. This weekend I plan to once again drop the pan and replace the seperator plate as outlined here.

http://www.explorerforum.com/forums/showthread.php?t=140987

It is my understanding that there are some TSBs with some changes and I'm going to track that down and make sure I do everything correctly. I'd appreciate any feedback. Please feel free to correct me lol. I sure don't want to have to do any of this again. I'd rather get back to adding offroad lights and performance enhancers lol. Thanks a bumch!

Jason

 

[BrooklynBay]

Welcome to this forum! You need a scanner which is capable of reading manufacturer specific transmission codes. What kind of scanner did you use? These transmissions use a pulse width modulated TCC solenoid, so your torque converter isn't fully engaged or disengaged during most driving. The PCM allows a certain percentage of slippage compared to older transmissions which had on/off cycling solenoids.

 

[sundownff]

Welcome to this forum! You need a scanner which is capable of reading manufacturer specific transmission codes. What kind of scanner did you use? These transmissions use a pulse width modulated TCC solenoid, so your torque converter isn't fully engaged or disengaged during most driving. The PCM allows a certain percentage of slippage compared to older transmissions which had on/off cycling solenoids.

Thanks for the welcome! I honestly don't know what kind of scanner it was, but I do know it was one of those $4000 jobs that good shops carry. He didn't mention any codes but did start talking about the torque converter and his hypothesis was that the transmission was overheating due to the lift and larger tires and causing a subsequent limp mode. I kinda dismissed this after thinking about it after a few days but I could be wrong. Should I go back and ask for specific codes? Not many guys in town have this kind of scanner. I work at AutoZone and I know we don't.

I understand pulse width modulation since i've done a little programming of servo motors and stuff so that makes sense but I really don't understand torque converter clutches. I didn't know there was such a critter until a couple weeks ago. I understand the fluid dynamics behind a torque converter, but could you describe the clutch to me? it seems like it would wear out with partial slippage, but this is a wet clutch I guess and I really don't understand how it works. How does the signal even reach the clutch? Thanks

Jason

 

[BrooklynBay]

The computer has to be reprogrammed for a larger tire size. It will throw off the shift points due to the larger turning ratio. The solenoid receives a PWM signal which varies the fluid flowing into the torque converter. The easiest way to describe hydraulic fluid dynamics is the analogy of applying light pressure to the brake pedal to slow a vehicle down compared to slamming on the pedal. The older vehicles had more of a "feel" when the solenoid would engage & disengage. The newer vehicles with PWM "baby" the apply grip of the torque converter so you don't feel harsh engagements or disengagements. The EPC solenoid also varies hydraulic pressure by using PWM.

 

[sundownff]

The computer has to be reprogrammed for a larger tire size. It will throw off the shift points due to the larger turning ratio. The solenoid receives a PWM signal which varies the fluid flowing into the torque converter. The easiest way to describe hydraulic fluid dynamics is the analogy of applying light pressure to the brake pedal to slow a vehicle down compared to slamming on the pedal. The older vehicles had more of a "feel" when the solenoid would engage & disengage. The newer vehicles with PWM "baby" the apply grip of the torque converter so you don't feel harsh engagements or disengagements. The EPC solenoid also varies hydraulic pressure by using PWM.

It sure does shift smooth as butter. Way nicer than my AOD. my tire size isn't extreme. I think its about a 30 inch tire, maybe a 31" but i'll check to make sure. The lift isn't much either. It's about a 3 inch lift from superlift. I haven't checked the vehicle speed with my GPS yet but everything seems to have been done right. The speed seems pretty much spot on but I'll check that too. Is this enough to mess up the TCC? Should I look into a programmer?

Jason

 

[BrooklynBay]

A transmission shop could read the codes & reprogram the correct tire size ratio. Check WWW.ATRA.Com for a shop in your area.

 

[sundownff]

I was able to pull some more codes with a better scanner. I now have a P0741 which points at the TCC not locking up properly.

Others include:
B1676- ABS? Battery voltage out of range (9V-19V)
P0136- oxygen sensor bank 1 sensor 2
P0171- lean bank 1
P0174- lean bank 2

I believe I've found my intake leaks causing the lean codes and I've replaced an oxygen sensor so all of that should be taken care of. The real kicker on all of this though is I'm getting right at 23 mpg even with these problems

With all the info I have, I'll be dropping the pan to change/inspect the TCC solenoid and separator plate.

 

[albi1cnobi1]

Any updates? Having the same issues. Well tranny anyway.

 

[sundownff]

I've taken care of all the other codes not transmission related. I haven't had time to drop the pan again but hopefully I can take care of that real soon. I honestly believe changing the TCC solenoid and the valve body gasket will solve my problem but only time will tell.

 

[sundownff]

Any updates? Having the same issues. Well tranny anyway.

It's long overdue but here is an update.

As I left off in my last post, I changed the TCC solenoid with no improvement. I did drop the valve body and noticed that someone else had already beat me to changing the valve body gasket so I left it alone as I did not see any rips or tears.

I continued to drive around town and some interstate for a couple of months with no additional problems not previously listed. I took care of the engine codes and was left with one transmisssion code. I decided to change the EPC solenoid because it was one of the last things I could easily take care of without dropping the transmission and it was a likely candidate for my pressure problem. I changed it and noticed no improvement.

About 50 miles later, I lost all pull at once and coasted to the side of the interstate. I brought it back to the shop that I work at and put it on the lift to see if i could find any clues as to what happened. I noticed a burnt fluid smell immediately and then noticed brown fluid dripping from a specific part of the valve body. All the rest of the fluid was a normal red color. No metal in the pan. I bolted it back up and checked flow at the transmission cooler lines.... no flow. I've lost all pressure and I don't know where to go from here without doing more homework.