T\C Sticking on - Need Help

[rob2337]

Hi guys, I have a 95 4x4 with a 4R55E trans. Just recently there have been two cases where I am in traffic and start to slow down and the whole vehicle starts to shake then stalls out. I am pretty sure that the torque is staying locked-up. The second time, the torque stayed locked-up for a bit while I tried to get moving in rush hour. Every time I put it into drive, it would stall. Even the starter seemed to have a harder time turning over the engine. I finally put the trans into second and that seemed to do the trick to get off the highway. After that incident, no further problems yet. I have searched the posts here and have found several possible causes. I was wondering which one would be the most likely before I start trouble-shooting. Is it possible for it to be an electrical problem? Do I have to drop the pan and check out the t/c lock solenoid? I know of a TSB from ford for the A4LD saying sludge might cause the valve for the t/c lock to jam. Would a transmission flush possibly help? Also if I drive with the O/D off light on, does this also prevent the torque from locking, or do I have to snip a wire or undo a connector. It is getting pretty cold here, and I'd rather not end up dropping the pan right away. Any help would be greatly appreciated! I don't want to end up on the side of the road with a permenatly locked convertor!

 

[Glacier991]

Hi Rob and welcome to the site. Your diagnostic instincts are good. You are pretty well describing a TC lockup problem.

Since lockup is electrically controlled, the first place to look is to see if the computer is being fooled into locking it up inappropriately. The computer relies on various inputs in making the decision to lock up the TC, mainly the VSS input (but there are others). Investigate the electrical possiblities first. Pull the codes and see if anything comes up. Once you are comfortable with the prospect that the computer is doing it's job appropriately, you can move on to mechanical issues. (Another place where the Transmission tester would be worth its weight in gold - substituting for the computer and ruling IN or OUT any computer/sensor involvement).

Mechanically the solenoid could have failed. (Ought to throw a code). The VB could have a problem. The gasket could be torn. (I am not where I can verify this, but will tomorrow. My recollection is that the TC lockup is INHIBITED in the 4R55E - meaning that lockup is WANTING to occur, but the solenoid STOPS it. if the solenoid fails lockup can occur unchecked. If a massive leak of that inhibit hydraulic circuit occurs, same result).

In any event, you will need to drop the pan to investigate these issues. Let's rule out electrical first. Let us know what you find.

 

[rob2337]

"My recollection is that the TC lockup is INHIBITED in the 4R55E - meaning that lockup is WANTING to occur, but the solenoid STOPS it"

So does this mean that I cannot disconnect the solenoid to check it out? It will just lock up 100% if the solenoid looses power? I have had some bad wire connector problems with the truck so the solenoid loosing power might make sense. Also does driving in O/D off prevent convertor lock-up?

 

[Glacier991]

IF my recollection is right, so are you. Disconnecting the solenoid inTHAT case, and ASSuming I my memory is right, would mean that disconnecting that solenoid would not tell you anything. You'd need to provide a 12v uninterrupted power source instead. Arghhhh trans tester!

 

[rob2337]

All right, I just pulled the codes from the X and this is what I got. 114 - IAC temp out of range (possibly normal code according to ford manual if temperature outside is really cold) and 639 (continuous memory) - turbine shaft speed sensor error. According to my manual, this would cause lack of torque lock-up, not lock-up. This is an intermittent serious problem - I hate intermittent problems! Anyone heard of the turbine shaft speed sensor dying on the 4r55e trans? Anyone know the approx prices of the sensors. I might just replace the sensor if it is cheap and see what that does. In the mean time I think I will just disconnect the torque lock-up untill the dealers open again.

 

[Glacier991]

Well.... the usual protocol is to pull codes in a computer controlled transmission problem case, and fix those errors. I'm with you as to what those errors *might* cause, and have trouble thinking they are the source of the problem.... still protocols exist for a reason... and also, the 639 code could just be a result, instead of a cause...

I was looking in the FORD factory manual, and the next step is to run "pinpoint test C". This test checks a myriad of things, all related to the TCC solenoid and wiring. It requires an NGS tester, a transmission tester, several cables and an ohmeter (hey bet you got ONE outta 3!).

In this test sequence you search for a bad TCC solenoid, wiring shorts to ground, and a short to ground within the solenoid. (Recall what I said about inhibiting lockup... when the solenoid is on, it will provide lockup, and a short to ground would complete the circuit hence causing solenoid operation. I find it interesting that there is a computer code for a solenoid failed ON in the TCC...but wonder if that is a foolproof code, ie. is it always thrown?

PCM can itself be suspect.

Moving on to other possible mechanical/hydraulic causes we have:

VB screws out of torque specification, gasket damaged (!) off location.

Separator plate damaged

TCC solenoid, stuck, damaged, o-ring damaged or out of bore. [Thinking possible bracket failure?]

TCC Solenoid and valve [Bore 200]

TCC control valve [Bore 201] spring damaged, stuck or bore damaged.

Lastly...

Torque Convertor Clutch Assembly - Internal malfunction

So... I don't know if hat adds anything. But that's kind of the laundry list.

 

[sparky2263]

The TCC solenoid is a normally open solenoid. It allows fliud flow through the passage until powered up. This seats the ball, causing pressure to build up behind it and moving the TCC valve in the valve body allowing fuild to flow to the converter clutch.

What you are describing is the TCC valve sticking in the bore. Very hard for the ball to stick in the solenoid (stick shut) as there is 60-100 psi of pressure wanting to push it back open. But, not impossible either.

 

[rob2337]

Well I followed all the ford pinpoint procedures on the service cd and found nothing yet(stupid intermittent problems). Still have that 639 code (continous memory), and nothing else. I gave up so I cut the TCC wire at the PCM and I am going to see how the X works like that. I took it for a test drive on the highway and it revs like 300 rpm higher. How much more heat do you think the trans will generate? It's pretty cold up here and I have a big trans cooler on it. I guess when I get a chance I will drop the valve body and inspect / clean it out. Has anyone else had a problem with the TCC valve sticking in the bore? I still don't know if it is a 100% mechanical problem in the valve body(sticking valve), or the pcm is actually sending a signal for it to lock when it shouldn't. I think I will hook up a test light to the pcm output and see when the signal is engaged / disengaged for the torque. As for the 639 code, I hope it was an effect of the torque locking, not the cause, because it looks like I have to drop and disassemble the trans to get to the sensor.---sigh - I hate intermittent problems; I wish it would just lock 100% of the time so I can pinpoint the cause.

 

[BrooklynBay]

I was looking at one thing on a website that had to do with an A4LD TCC applying too early. You could do a search on that website for your model transmission, but if you read the article, you wll get an idea of a possible solution to your problem. Here is the link: http://www.transmissionspecialty.com/parts/parts/56995A.htm

 

[rob2337]

** UPDATE***

Well it is not an electrical problem because it just did it. I got off the highway and it stalled instantly. After restarting it would stall in any gear selection. Finally after playing I found that it would work if i put it in reverse first then into first. Also if I downshift manually to a stop it doesn't seem to stall. I have no choice to drop the valve body (i guess). What parts do I need for the job besides filter and gasket. Springs? valve body gasket? etc? Also I noticed when checking the fluid today, that it isn't in the best of shape. Would a trans flush be a better start? I remember having a 1987 v6 ranger that had some trans issues, we changed the fluid and it went away! Any help where to start is welcome

 

[Glacier991]

If you pull the vb, I would suggest you go ahead and rebuild it. As the fluid sounds cruddy, I think I'd do a flush, and then drop the pan and remove the VB to rebuild it. While it is out you might want to go ahead and replace the EPC and TCC solenoids, they do wear out. I'd suggest you add a superior kit. When you put it all back together and install it, put in a new FRAM microfelt filter. The 5R55E rebuild dairy applies to the VB you have as well.

You will need sep plate gasket and main gasket (2 gaskets in all) You CAN reuse the low/reverse servo gasket, or buy a new one. The Superior kit has a new seal for that servo, install it. You will need the Superior kit, and also the filter. You'll probably spill a couple quarts of fluid too.

 

[rob2337]

Well I am going to order the #K4R/5R55E Superior shift kit tomorrow and do a Trans flush. This should most likely solve the problem right? While I have the valve body off is there anything else that I should change or modify? Thanks for all the help!

 

[Glacier991]

There is a Sonnax Boost Valve upgrade I can suggest. It is not in the MUST DO mods, but that's about it.

I am making no guarantees about solving the problem, but I wouldn't suggest it if I didn;t think it was worth trying.

 

[BrooklynBay]

Sonnax makes a lot of different types of boost valves. Some have a high boost for the 4.0, and a low boost for the 3.0. I don't know why it would make a difference though. They also make an oversize boost valve for some worn valve bodies. Another new thing they make is a side disk stopper cover that has an O ring around it. They still sell the standard factory style too. It's supposed to help prevent leakage from the end of the bores of the valve body.

 

[rob2337]

All right, I just finished doing a tranny flush and added the superior shift kit (minus the coast clutch replacement as i could not get the end plug out of the bore). On my way home, presto! The freaking torque locks up again! More so now then before the rebuild. The only way do disenage it when it locks is to either drop the tranny into first gear, or floor it and when it get enough rpms to kick down, the torque disengages. I cleaned the TCC solenoid bore really well. However, I did not replace the solenoid because it was like $300 from Ford. However, do the symptoms I describe above point towards a bad TCC solenoid. Again no codes. If it fails, wouldn't it not engage, not lock up when ever it wants. Any sugestions guys? Drop pan again, and install a jobber TCC solenoid??

P.S. The shift kit makes all the shifts nice and firm.

 

[Glacier991]

Hmmm, I'd say at this point you have 5 possible culprits. Bad inputs to the PCM, Bad solenoid. Bad wiring harness, bad TC, bad PCM.

 

[rob2337]

ok, well i think i can rule out the inputs to the pcm / pcm problems. At first when the problem started, I cut the wire at the pcm to the TCC solenoid. All I got was a flashing o/d off light and a torque that was locking up. I guess there might be a short to ground in the wiring harness, but that doesn't explain why when I down shift to first it disengages. Also, a bad torque convertor wouldn't always release when down shifted to first. So this leads me to believe three things. The problem must be in the control valve body. Either somthing is sticking in the valve body, or the Solenoid is bad. Would a bad solenoid fail in the on position, has anyone seen this? I am a student and can't afford too much $$$ in parts. Should I try to replace the TCC solenoid, or I was looking on E-bay and they sell the whole valve bodies for like 50$ with all solenoids (used), 1/4 the price of a new TCC solenoid. Does anyone know why the torque will always disengage in first, and not in drive. Is there a bypass hydraulic circuit that is activated when in first for the torque?

Thanks in advance for the help!!

 

[Glacier991]

You ask excellent questions. I wish I had equally excellent answers. I cn find nothing to confirm this, but it would not surprise me if the PCM will not engage the TC in manual first gear.... with the Digital trans range sensor it know what gear you select and it would be easy to program that function in... but I truly do not know.

This one is somewhat mystifying. You might try swapping in another 4R55 valve body. Tranzparts in Florida is a reliable supplier of used VB's.

Still, the fact you have codes troubles me. The accepted practice is that you fix all codes before you look further into computer controlled tranny's. I understand what you have done and you have done all the smart things. I'm a little lost here myself.... but I keep getting stuck on the existence of codes. Wish we could put the trans tester on it.


ps. Just found it, the TCC will NOT lockup in 1st gear. Electrical or hydraulic I have yet to find.

 

[sparky2263]

Fluid flow to the TCC is not allowed in first gear. He is stating it will do it with the TCC wire cut, so, it has to be a hydraulic problem. He also states that it won't do it when pulled into manual low, and manual low cuts off fluid flow to the TCC, so he's okay there.

I have read and re-read this thread. I have been here before. And it means I missed something. When that happens to me, I throw out (of my thinking) everything I have done, and start over fresh.

I beleive there is a restriction to flow in the TCC apply circuit. If this is missing, the flow can overcome the leak the TCC solenoid creates and move the TCC apply valve even with the solenoid de-energized.

I will investigate this later today.

 

[rob2337]

I agree with sparky2263, there must be a restriction in the flow which causes the T/C to engage. My question is that I can get a used valve body for $100 with all the solenoids (cheaper than a new tcc solenoid). Is this my best bet in solving this problem, or could the restriction be somewhere else in the transmission? Is it time to suck it up and bring it to a shop? One last thing I discovered today was it only causes problems once the transmission is warm.