Question on E40D torque converter is locking, and unlocking

[DragRag]

Here is what my trans is doing. I can drive down the road for an hour or two, then the trans torque converter under regular driving conditions will just unlock, and then relock. It will do this over and over, sometimes seconds apart, sometimes minutes apart, and might stop again, and start doing it all over again later. I take mainly long drives in this truck, and two all the time with it so it is annoying, and no doubt not good for the trans or T.C. Any ideas on what might be causing this. I took apart and greases the trans plugs, they were clean, and no burning anywhere. I also just replaced the brake light switch since pushing the brake pedal in while under throttle creates the same scenario, but mine just does it all by itself without touching the brakes. I am trying not to buy another trans since I am going to have to out one in my 97' power smoke as it is. Shed some light please if you might know what is doing this.

Everett

 

[Russ]

I think you're on to something with the brake lights, I replace the rear bulbs just to be sure, might just be a bad bulb or a bare wire.

 

[Highridge]

x2 on the rear bulbs. I had a bad ground on one of my taillights and it would do the exact same thing.

 

[icanfixall]

I'll bet you have a stop lite on either side in the back thats bad. When I rebuilt my motor on my test run afterwards I got the lock and unlock every time I used the right turn signals. I changed both blubs and found the stop filament broken and touching the turn signal filament. Sure had me thinking I crossed up some electrical when the work was done. Did you clean and grease the three plugs under the master cylinder on the drivers side fender well. Also there is an electrical connection on top rear of the trans. All together you have 7 connections to clean and grease...

 

[zacky6661]

x2 on the rear bulbs. I had a bad ground on one of my taillights and it would do the exact same thing.

im pretty sure i have the same problem, i cant tell if its T.C. lockup/unlocking or just my tranny downshifting unnecissarily, i have a C6 with a shift kit and ill be cruising down the road and unless im up in the rpms itll just randomly feel like its downshifting.

i do know the p.o. did a crappy job of tapping into my brake light system for power to the tow package setup, and every once in a while when i hit a bump i lose my right brake light.

 

[sootman73]

im pretty sure i have the same problem, i cant tell if its T.C. lockup/unlocking or just my tranny downshifting unnecissarily, i have a C6 with a shift kit and ill be cruising down the road and unless im up in the rpms itll just randomly feel like its downshifting.

i do know the p.o. did a crappy job of tapping into my brake light system for power to the tow package setup, and every once in a while when i hit a bump i lose my right brake light.

yours doesn't have lockup. No c6 has lockup. yours must be downshifting or slipping but there are no electronics that control your trans that would cause that. Yours is vacuum controlled only. you have three gears where as the, well here

E4OD - Electronic 4 speed with OverDrive

 

[topgunn]

My trans was doing same thing. Any connection- cruise control, brake switch, bad bulb, throttle position switch are all possible candidates. Cruise control drops T.C. out when braking. I found that a brake wire was shorting out when I was putting body lift and raised bed to install lift donuts.

 

[zacky6661]

yours doesn't have lockup. No c6 has lockup. yours must be downshifting or slipping but there are no electronics that control your trans that would cause that. Yours is vacuum controlled only. you have three gears where as the, well here

E4OD - Electronic 4 speed with OverDrive

do you think my vacuum pump could be going out then? or maybe the fact that the previous owner put in an aftermarket tranny fluid filter outside on the transmissions cooler lines, but when he replaced parts of the lines with regular vacuum hose... maybe its swelled or somthing from absorbing fluid. idk. either that or that filter needs to be changed.

 

[LCAM-01XA]

x2 on the rear bulbs. I had a bad ground on one of my taillights and it would do the exact same thing.

Is that why LED brake/turn bulbs can cause the PCM to go bonkers, not enough current flowing through the circuit? Cause I got a pair I really wanna install in my truck, but I recall some folks had issue with LEDs... Actually how does the PCM know the brakes have been applied, does it monitor a voltage drop across the brake lights circuit, or what? I know for my manual TCC lockup I tapped into the BOO switch and feed the 12V signal into a 5-pole Bosch relay so that when I step on the pedal the relay opens and the converter unlocks regardless of whether the brake lights actually come on or not. Also assuming I stick the LEDs in there, is TC lock and unlock the only potential issue? Cause I can live with that, as my TCC is on a full manual switch and the PCM is fed a dummy signal through a 20k resistor, so I don't really care if it wants to lock and unlock the converter randomly as there's physically no connection between the PCM and the TCC solenoid no more, just as long as there are no other adverse effects such as entering limp mode (which it shouldn't do, but one never knows)...

do you think my vacuum pump could be going out then? or maybe the fact that the previous owner put in an aftermarket tranny fluid filter outside on the transmissions cooler lines, but when he replaced parts of the lines with regular vacuum hose... maybe its swelled or somthing from absorbing fluid. idk. either that or that filter needs to be changed.

If your vacuum pump was bad then you'd have poor brakes assist as that's what the pump is mainly for. Common failure points in your setup are the VRV on the side of the IP (the thing with two vacuum lines hooked up to it) and the line pressure modulator down on the passenger-side of the transmission (cylindrical looking thing again with a vacuum line hooked up to it) - there is a test procedure for the VRV that someone will probably post soon (I don't have it saved), but for the modulator you can just pull the line off and see if there are traces of trans fluid inside it (that indicates a leaky modulator).

 

[oldmisterbill]

I had the same symptons finally I cleaned every (every connection-the 3 under the master cyl-the main power relay for the computor,every plug I could find.I don't know which one caused it but my problem left 6 years later it is still gone ( so is the owner!)I greased them with diaelectric silycone.

 

[DragRag]

I had the same symptons finally I cleaned every (every connection-the 3 under the master cyl-the main power relay for the computor,every plug I could find.I don't know which one caused it but my problem left 6 years later it is still gone ( so is the owner!)I greased them with diaelectric silycone.

Did that and changed the brake light switch, nothing has changed yet. I will check the rear bulbs, and wiring there tomorrow.

 

[OB_WAN]

gonna throw something else out there. I had symptoms in my trans where I'd be cruising @ freeway speeds ~70mph and all of a sudden it acted like it just freespooled(had cruise set and it acted like it went in to neutral) then would lock back up. Guessing this isn't your symptom but in case it is...

I was low on transmission fluid. As soon as I filled it back up, trans works great. If you do indeed have the same symptoms I was experiencing, your bulbs/wires are good, and your trans fluid is good. you might want to think about replacing the filter(restricting flow) before worrying about the really expensive parts like the pump.

 

[rjjp]

I would try disconnecting the batteries overnight, mine does this about once every 6-8 months and that generly solves it. On a side note, LCAM, the LEDs will cause hyperflashing unless you either put load resistors or a differnt flasher in.

 

[LCAM-01XA]

Yeah, electronic flasher, got one of those rolling around here somewhere too...

 

[oldmisterbill]

Just a thought -If you install a convertor lockup switch (1 wire spliced to the compoutor thru the swutch to Ground -you will know if it is electrical or not.It will stay locked above 30 or so with no unlocks .