Archived Torque Converter lock up issues

[blasterfdc]

I'm in dire need of assistance. I really want to go camping memorial weekend.



Truck was experiencing TQ Shutter especially under load. Decided to bite the bullet and have it rebuilt. A local shop Has gone through the entire trans, triple disk TC, billet input, all new parts in trans, shift kit etc. When he finished and test drove it, the first couple times up through the gears it shifts perfect. then the third time he said the TC wasn't going into lockup unless he comes off the gas pedal a couple times and back on. then it locks up great. Once it's locked it's locked solid. scanned the computer and the computer is giving the signal but nothing happens until you touch the gas. he's rebuilt the VB again, then replaced it with a new/rebuilt OEM one from the dealer - no change. had the APPV scanned - nothing. short of pulling the trans totally apart again, I don't believe it's in the trans.



everyone is at a loss, the trans shop, an electronics shop, the dealer... ... ... . no clue



i've seen this issue on multiple forums but never a solution.

 

[cerberusiam]

Replace the TC, that is usually the solution. The lockup is computer controlled thru a solenoid on the VB. If the computer demands lockup and it doesn't its in the VB harness, solenoid or TC. If you replace the harness and the solenoid and it still is intermittent it is almost always a TC issue.

 

[blasterfdc]

Torque Converter Is Brand New TripleDisk. It Will Work 3 To Five Times first thing then right back to not locking up unless you play with the gas.....

 

[cerberusiam]

Like I said, replace the TC. It is entirely possible there is a problem with the seal or apply piston in the TC that is causing the issue. If everything else looks good, its sounds like they have replaced the critical parts, suspect the TC.

 

[fox]

I've seen a lot of brand new parts that were defective.
I agree with cerberusiam.

The converter MAY loosen up and work in time but I would ask for an exchange NOW.

 

[blasterfdc]

I hear you, I'm just trying to understand how the torque converter could be the cause of a discrepency like this. From what I understand, when hyd pressure is applied to the converter under normal operation it forces the clutch away from the drum. when the computer signals for the trans to go into lockup it actuates one of the solenoid in the VB which releases the hyd pressure and applying the clutch locking the TQ. if the TC is working first thing and when you lift/reapply the gas. Seems like it would either be electrical or something not allowing the hyd pressure to release when commanded. I'm thinking that varying the gas (RPM) also varies the pressure and releasing it. of course that is just my uneducated guess.



do you know how the TC could cause it to hold pressure like that, that is if I'm understanding the operation correctly

 

[cerberusiam]

IIRC, the way the TC work sin fluid coupling is the flow of fluid actually keeps the clutch piston disengaged. To apply the clutch the flow direction is changed so it now against the back of the piston and that applies it. The solenoid just reroutes the fluid thru a different circuit to apply lockup.



What can happen is the lip seal can get rolled or torn and the piston itslef may be out of round or dragging. As the trans warms and the fluid is not as heavy it won't apply correctly anymore and\or the expansion jams the piston.



What I would do is a dd a mystery switch to the lockup circuit, pin #6 on the trans control harness, with the resistor to stop codes. When it refuses to lockup normally try the switch to see if that will work consistently to get it to lockup. If it does lock all the time with the switch it is something in the ECU circuit that is not grounding correctly. To apply lockup or OD the ECU simply grounds the sense circuit. It might be demaning lockup but if the circuit does not ground correctly the ECU might not see that.



If the TC does not lockup consistently with the switch it is an internal transmission issue and likely the TC itself. PLEASE post back what you find to be the problem with this as it does happen a lot on the 2nd and 3rd gens both. There are 2 threads, yours makes a 3rd, of rebuilt or normally working transmissions do this exact same thing.

 

[blasterfdc]

Thanks Cerberusiam, a lot of good info. I now he ran a ground directly to the pin you mentioned and did get it to lock up. I think he said it wouldn't work above 40mph, but I could have sworn it did when I rod with him and he grounded the pin. This guy is getting frustrated as am I. He's going to give it one more try and then he says he's out. He said he's going to rebuild my original TC and put it in and also check the pump out. if that doesn't fix it he said it has to be in the computer system or electrical and he doesn't have the expertise there, he's strictly a transmission guy.

if the TC doesn't work I guess it's back in my hands to try to fix and I'll try the switch you mention above.



so if I do this switch and it does lock when ever a ground is applied you say it's a ground fault in the ECU circuit and if it doesn't lock up it's in the transmission right? what do you recommend at that point, it's almost impossible to find a bad ground.



what if it only won't lock above a certain speed?



did I mention the truck only has 60k miles on it.....

 

[cerberusiam]

If the lockup switch will not lock it consistently, no matter the mph, the problem is not electrical. Something in the TC or the lockup circuit is not working correctly.

Do you have OD all the time and consistently? It is not dropping out of OD randomly?

Both the OD and lockup solenoid are powered all the time from the trans control harness via the trans relay. As long as there is power there and the solenoids are good a mystery switch on either OD or lockup will engage the function consistently. If the trans realy or power supply is bad the trans will go into limp mode and stick in drive with OD or lockup, and, the ECU will set DTC's and a CEL. Both functions work by the ECU grounding the sense circuits, pin #6 and #7. By putting the switch in you are bypassing all computer control and manually demanding the function. If that function does not work consistently then the problem is mechanical in the trans, no other way to diagnose it and it is his problem to fix.

Unless he has a lathe and a lot of knowledge of the TC he is not rebuilding it, and, I would say that would be a red flag. If he built the one that is in there now that is even a bigger red flag.

If it won't go to lockup over 40 mph there is a problem in the trans, likely in the TC with pressure bleeding in where it should not. Under 40 mph ther eis not a lot of TV (apply pressure). The more throttle you give it the higher that pressure goes and that may contribute if something is built wrong. That is not electrical, all mechanical.

Good luck with it. I hope does you right. If he can't get it right I would go to TRE in Virgina Beach and let them do it right or trouble shoot it.

 

[blasterfdc]

I've tried it both in tow/haul and not, no difference. O/D works fine.



His father's shop builds the TCs, not sure what set up he has but he builds a lot of them and has been in business for decades. The one that came out of the truck was the original one. The original gripe I had what chattering/slipping while towing. i know now it was the TC slipping, they cut it open and the clutch was burnt. the rest of the trans was in good shape but chose to build it while it was apart.



I lived in Va Beach for almost 19 years. who's TRE are they a trans shop?

 

[cerberusiam]

TRE Diesel Perforamnce, http://www.trediesel.com/Home_Page.html. Tim builds a mean transmisison for diesels.


Sounds like your guys should know what they are doing if they build that many. Time to throw away the suspect parts and go with something known good.

If OD works fine then the solenoids are powered and that is all good. Is it possible it has one bad solenoid? Maybe, just not likely if the solenoids and harness was all changed.

 

[blasterfdc]

He has actually changed the solenoids more than once. even put in a new VB from Dodge. I'm so frustrated. after he tries this TC, if it doesn't work I'm going to get it back and try a couple things and maybe make a trip down to Va Beach to visit some family and stop by TRE. I hate to have to pay for this twice... Feeling like I should have just traded it in, but I love this truck.

 

[cerberusiam]

I am thinking positive thoughts for you. The TC will fix it... ... . the TC will fix it... ... . the TC will fix it... .....

The 48RE is dead simple to build and maintain compared to the 68RFE. With all the emissions garbage and the complexity of the newer ones, not to mention the cost, all the fun has gone out of trading up.

I keep looking... . and walking away.

 

[blasterfdc]

Are there detailed instructions on the switch hook up. you mention a resistor, I found one that installs a switch to give a direct ground to the trans when selected and then a bypass wire on the relay. Iis this what you are refering to?

 

[cerberusiam]

Don't jump the realy, if you have any shorts it will melt the wires all the way to the trans.

Scotchloc and 18 gauge wire to pin #7 of the trans control harness.

Run the wire to one side of single pull single throw switch.

Wire a 1 or 1/2 watt 33 ohm resistor to the other side of the switch and then from the other end of the resistor to a chassis ground. You want the resistor between the switch and ground.

This will ground the sense circuit and activate the soelnoid. It won't trip the relay or trip DTC's that would shut the relay down as the resistanc ein the circuit is the range the ECU is looking for. You cannot dead short the sense switch or the trans will likely go into limp mode or the circuit shut down in the ECU. If the switch was wired without a resistor before this may be why it quit working over 40 mph. The ECU just shut the circuit down becuase it sensed a dead short as soon as it saw it could go to lockup.

 

[blasterfdc]

couple questions.



Scotchloc?



if the truck goes into limp mode, how do you reset it? I have the capability to reset codes via my smarty.



What exactly is limp mode? what happens if the circuit shuts down the ECU? that sounds scary? does it reset by shutting the truck off and turning back on once it's corrected?



He did short the circuit without any resistor back when he first started troubleshooting it. how would he have reset it or is it still thinking there's an issue?

 

[cerberusiam]

A run and tap connector to tie into the line, like this http://www.bing.com/shopping/3m-sco...pq=Scotchlok 567&qpvt=Scotchlok+567&FORM=HURE.

If the DTC is critical enough limp mode will shut down both the OD and lockup circuit. What you get when you tap the sense side of the circuit is resistance to low error under 5 ohms and it can shut down just that circuit or go to full limp mode. It depends on the verison of programming in the ECU and how long it sees the fault as to what steps are taken.

Once you remove the short and shut the key off it will reset itself. You will have to clear the code with a Smarty or something like that.

It is possible by not putting the resistor inline it has caused issues in the ECU. It takes very little amperage to toast the ECU circuits. They are never meant to see more than 1/2 amp or so of current, all the load is taken by the solenoid. The sense circutis are rather fragile to surges or amperage. One of the reasons you never weld on the truck with the batteries connected, never pull a battery cable with engine running, and never boost another vehicle with the engine running. All it takes is one errant short or surge and there goes the ECU, FCM, and any other number of modules.

The trucks with the TIPM's are worse. Short a trailer light too many times and you cannot reset that circuit, you have to spend $700 to replace the TIPM to get the light circuit back working.

The mystery switch with the resistor will tell you if it is mechanical or electrical and not hurt anything. I have one on mine for 150k and use it frequently. If it is the ECU circuit you will find that when it won't lock automatically but will when you use the switch.

 

[blasterfdc]

He didn't get to it today. Called a friend instead who used to work at the local dodge dealer. they ran the VIN to see if there was any reports of other people having the issue. Mentioned that this year truck has a mode where if you are in 2nd gear (which we are not) you can lift the gas twice and make it go into lock up. Coincidence? I don't know, now he's wondering if the computer is the issue. I can't see the computer being bad...



the old torque converter has been rebuilt just needs welded up before he can put that in.



and it continues

 

[cerberusiam]

Mine will go into lock up in 2nd gear with a steady throttle once the engine load drops low enough, no need to play with the throttle. Not sure what all that is about.

You have to try the lockup swithc to see if it is mechanical or electrical. My guess is a problem with the TC but its really hard to tel.

 

[blasterfdc]

but how do you explain the lifting and reaplying the gas and it comes on, that makes me think hydraulics.