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Hey all,
As the title says, I have tried everything short of a rebuild to get the torque converter to stop bucking when in lockup. My car feels more like a galloping horse than a car when I'm on the highway and in lockup mode. I know that you can disable the lockup feature by disconnecting the wiring harness that goes into the front of the transmission. If I disconnect that harness will it harm any other transmission functions? A reputable mechanic told me to disconnect it and the only thing I'll lose is a few mpgs from my fuel economy. However, I noticed that there are eight pin connectors on the harness which would indicate that there are other transmission signals tied to the harness. The transmission is original with 132k on it and I am currently doing a considerable amount of highway driving. The fluid in the transmission does not smell burnt. Can anybody tell me if its truely safe to disconnect the harness?

That reputable mechanic doesn't know what he's talking about.

That connector controls TCC solenoid, ALL of your shift solenoids (which you need) and the TC PWM (pulse width modulator), oh and the trans temp sensor. You unplug that, you ain't driving. Now, for an interim fix, you could just snip the wire that feeds the TCC solenoid, tape it off, and be on your way, but I recommend you get that properly fixed ASAP.

When you say you tried everything, did "everything" include a bottle of lubeguard or equivalent friction modifier? I had exactly the same symptoms and thought I was facing a rebuild until a shop told me to add a bottle.

I'm no tranny expert, but I'd assume that if you are going to disable the lockup, you will have to remove the one wire that controls lockup. Of course, I'm no expert, so I probably stop talking about disabling lockup now.

However, Ford once disabled my lockup on my 92 Grand Marquis internally to solve a bucking problem caused by lockup. I still passed the emissions tests, at least before the IM240 tests. I don't know if it would pass now because the lockup has since been reconnected. The lockup tends to hold even at low RPMs for fuel economy. I later found that regular MAF cleaning would solve the problem.

Hey Brad (or anyone knowing) how hard is it to replace the TCC valve/solenoid? This is a problem I may have as well...

The subframe on the trans side has to come out, as does the drivers axle. The trans mounts...both the front and rear ones...need to be unbolted as well. The trans does not need to come out, but you do have to lower the trans enough for the side pan to clear the body, which needs to come off the trans so you can get at the valve body and whatnot.

Andrew did this with a flip, but he did a lot more work.

Thanks for all the advice. I figured I would ask you guys before disconnecting that as I knew that 8 pin connections meant other things were going on too. When I said I did everything to try and solve it, I meant that I switched MAFs, I changed the fluid, I even added a bottle of friction modifier and a bottle of lucas transfix. There is no more room in the trans for another additive. Anyways, which wire(s) do I cut to disable the lockup? I am most likely going to cut the wire as this is situation is going to cause my otherwise good functioning trans to grenade. I don't think this car is worth a rebuild at this point, it has given me more than I could ask for so I am going to ride out the storm. I may wire a switch in series with the cut wire so I can connect it to pass emissions and have the ability to re-connect the wire should I happen to fix it.

From my 1997 H-body FSM:

C129 (transaxle connector)
Pin C = TCC PWM Sol Valve Control (colour = BRN)
Pin D = TCC Sol Valve Control (colour = TAN/BLK)

I'd say you should be able to remove these wires without cutting. I've removed wires by separating the connector and using a small screwdriver to release the tab holding the wire in the connector. This way, you could reinstall the wires easily.

Enslow, I take it you had a similar problem with your converter. How long have you had yours disconnected for? I am willing to sacrifice fuel economy for a trans that will last longer.

Always remember, results may vary. Just FYI, don't assume because person "a" lasted 10 months you will.

Tuffguy610 wrote:Enslow, I take it you had a similar problem with your converter. How long have you had yours disconnected for? I am willing to sacrifice fuel economy for a trans that will last longer.

The problem I had was in my Grand Marquis. The solenoid was disconnected internally by Ford for a few years. I actually liked how it shifted because it didn't drop to the low RPMs which eliminated that delayed "downshift" as it would disengage the lockup. It was reconnected when I had the tranny rebuilt at about 250000km.

The problem with the AODE in the Grand Marquis was different from the Lesabre. I had a dirty MAF that underestimated the amount of air entering the intake at part throttle. As a result, the mixture leans out, especially just before a shift change. I was getting horrible pinging and chugging when the computer refused to disengage the lockup. With the MAF cleaned, the computer releases the lockup sooner.

In the Lesabre I also had the same problem you are having, except that the friction modifier did solve the problem. I assume that I will eventually have to have it rebuilt, but hopefully it'll last a few years. I would assume that the two wires I mentioned could be released from the connector at the transmission fairly easily with no harm being done to the tranny. Because it looks like it could be done externally, you could probably try it and see how it goes. I'm sure you're check engine light will go on when you remove the wires.

However, that is an assumption. You'd better check with some one who knows better if removing those wires is safe or not.

We had the TCC and EPC solenoid on our '99 i think two years ago.... paid around $435 to have it done.

Here is the problem with what you are wanting to do.... This Trans is intended to lock up... If it never locks up it will overheat and will in due time burn up...

If your mechanic is reputable why is he telling you that unplugging the TCC will only cause you to loose a few MPG's when in fact this is not the case...

Jrs3800 wrote:Here is the problem with what you are wanting to do.... This Trans is intended to lock up... If it never locks up it will overheat and will in due time burn up...

If your mechanic is reputable why is he telling you that unplugging the TCC will only cause you to loose a few MPG's when in fact this is not the case...

Thanks for that info Jrs. Can you explain in fairly simple layman terms why it would heat up? I actually would have guessed the opposite.

Its like a turbine that uses a fluid coupler of sorts... Not really sure how to explain it..

You are in a certain word sheering the fluid, The converter turning and multiplying torque as it does creates heat and a good bit of it.. When the converter locks up you are no longer multiplying torque, its like a standard trans at this point so the heat in the trans will drop off... Keep in mind that the converters of today are tighter than the converters of yesterday.. These transmissions will overheat without the TCC...

You guys are free to disconnect the TCC PWM and TCC Solenoid wires, but be ready for the trans to overheat and cause other problems.. as well 260F is Trans Limp Home...

There are some old transmissions that you could do this to... But the THM440-T4( 4T60 ) and 4T60E are really not among them...

Thanks, actually what you said makes tons of sense! I hadn't considered that lockup removes the work that the fluid does to multiply torque.

Thank you all once again for your advice. I am having trouble disconnecting the C and D pins from the transmission harness. I have sat in the driveway for a half an hour with a paperclip and small screwdrivers but I cannot seem to figure it out unless I want to cut the wire. Any advice?

After what I learned from Jrs, I would not disconnect the lockup solenoid. It sounds like you'll have to just get the problem fixed internally.