4L60E No 4th and TC lockup

Simptoms: No 4th or torque converter lockup. When the car gets ready to shift 2nd to 3rd it will kick down to first unless you hold the throttle a little harder and let off. Check engine light does not come on and there are no codes when I hook up a reader.

Actions (In order)
-Replaced with used trans which worked perfectly for about 200 miles. Then trans went back to doing the EXACT same thing.
-Replaced PCM with known working used one.
-Replaced Vehicle speed sensor
-Replaced throttle position sensor.

Any ideas??

Did you reuse the original torque convertor??
Still Thinking
Jim Gordon

No. I changed the torque converter at the same time, flushed the lines, and put a new filter in the trans.

3/4 solenoid?

Is the throttle valve cable properly adjusted as per factory service manual? Maybe adjusted "tight". How does the 1st. to 2nd. shift?

Joel will know, give him a chance to chime in.

Mike

I have both factory service manuals. I haven't checked the throttle cable adjustment but can do that next. 1st - 2nd shift is perfect at about 15 mph. I'll have to read up on the 3-4 solonoid. I seem to recall that a bad trans temp sensor reading hot would lock out 4th and TC but doesn't explain odd 2nd - 3rd shift. Roadmasters and Cadilacs had an external torque converter tem sensor. I tried disconnecting that and running it both open and jumped to closed circuit.

a bad brake switch (behind the pedal) will stop the TC lockup. Not sure about 4th...

The brake lights work correctly and looking at the wireing diagram it APPEARS to be the same circuit. I think there's a code for the switch on the on-board diagnostics in the climate control. I'll check that as well.

Mike is right, wait for Joel (Sherlock9C1) to chime in..... he is the expert in this area....

Tim

Oh this is easy. You've got a bad Huzadinger linkage connected to the whatchamajiggy. Next time you drive it, try to lift up on the fritzeldurfer with the left turn signal on while rolling the driver's window down and see if the problem goes away. If not, your incombobulator might be gunked up.

The other thing I usually recommend is to take some Nyquil get some sleep and see what happens. Actually, maybe I should do that.

If you're really adventurous, you could try enabling the 5th gear solenoid. GM kept that disabled in the factory programming because big companies like conspiracies for no reason and adding parts that do nothing.




Seriously, you didn't even state what kind of car you're working on, how many miles, what else has been done to it. Just off the top of my head, if swapping the trans causes the same problem, then you either have two bad transmissions, a wiring harness problem, or an input to the PCM is bad. Datalog the car and see what the PCM is commanding the trans to do. Many many 4L60E problems are caused by electrical problems that may or may not be inside the transmission.

EDIT: This link may help your diagnosis.

"Burping is caused by too much gas in the fuel system"

Classic!

WOW Joel...... To much caffeine??

I'm sorry I'm kind of new to the forum and havn't filled in a profile. The car is a 96 Roadmaster estate with 150 K miles. The trans supposedly came out of another B body but was older since it had the earlier vehicle speed sensor.so I had to change out the tailshaft housing. I've taken the car to a transmission shop who just told me it was junk and needed rebuilt for $1,500. I find it hard to believe that two transmissions could fail in the exact same way. I'm getting down to shooting for bad wires, bypassing the PCM and cycling the solonoids with switches to manually shift to 4th (TC is easy but 4th is a bit trickier), or parting the car out. I just posted this as a last ditch since nothing in the manual or anyone I know has seen just this kind of thing.

I hate shops that say that. Most probably say that to cover their butts because with 150k miles, there are probably several things getting close to failure. In their defense, who wants to pay $250 to have a problem fixed when they may be back a month later with a total failure? I got bit quite a few times on cheap refurbs where some OTHER part I never touched broke for no reason and I got blamed because I had been in it.

Wow, you are the first person I've ever actually known to manually run the solenoids (Which I recommend for diagnosis if you don't have access to a monitor/datalogger). Just run 1-4 and then come to a stop, and then manually step your way back to 1st (do not just go directly to 1st - the 4L60E's hydraulics are sequential).

Just two switches to ground are all you need. use the Factory Service Manual chart below (I may have the solenoids switched but you get the idea).
Gear A/B
1: On/On
2: Off/On
3: Off/Off
4. On/Off

One other option is to put small lights or LEDs on the solenoid feeds , put them on the dash and watch when they cycle. This will tell you if the PCM is commanding 4th.

Also, if you aren't datalogging or monitoring what the PCM is commanding, you are not looking at HALF of what's going on. You really, really need to do this if you don't do the LED trick above.

BTW, are you sure you don't have some sort of linkage or PRNDL switch misalignment so the PCM thinks you're in D?

What color was the interior of the transmission harness connector, purple or green?

My connection is slow tonight (and perhaps so is my brain).

Several of you have asked me what I recommend for transmission pressure gauges.

Here's the one I have and use:
TRANSMISSION-TOOLS-PRESSURE-GAUGE-HD-STAINLESS-300PSI

One other thing. Did you recently install a different pan on the transmission? There is a hole in the pan rail for the drain of the innermost chamber of the servo when 4th gear applies. There is at least one aftermarket pan that allows the pan gasket to partially or completely block that hole, and if it's blocked, the servo can't engage 4th gear. I've only heard of this happening a few times but it's worth mentioning.

- I used the same pan as came with the used trans. I put a new gasket on it so perhaps there is a problem there. I can check that and the color of the connecter if/when I pull the pan next.
- I've adjusted the shift linkage up and back a bit to to see if the trans thinks it's in D.
-i've thought of the LED idea and was hoping I would find the problem before I needed to get to that. I'm pretty sure it will show that the PCM is commanding (or not commanding) the weird shifts. I was thinking of making up a loom with a male/female connection and putting it in line between the loom and trans. Once that is done and I have the wires in the cockpit I can add switches to energize the TC solonoid so that will work. I could also energize/de energize the solonoids to make the 3-4 shift.
-Apparently there is still no quick fix to this.

OK, here's the latest. I spiced a set of wires in parallel with the trans wires to the A, B and 3-2 solonoids. I ran the wires into the car, hooked a voltmeter to them, drove around and recorded the readings. When the voltage was less than 1, I presuming that the circuit is closed by the PCM and therefore ON. When the voltage is over 12, i'm presuming the circuit is open and therefore OFF. I was pretty careful and had a friend check my work and we used the original GM factory manual to determine the wireing connections at the PCM. The actual gear the car was in was determined by pulling the tach up on the climate control. For example in what was the last shift of the sequence, the engine was turning about 2400 rpm at 55 so i'm saying that's 3rd not 4th. The results:

1st: A= 0.25v, B=0.25v, 3-2=0.70V gear actual=1st
2nd: A=14.25v, B=0.25v, 3-2=1.36v gear actual=2nd
3rd: A=14.25v, B=14.07v, 3-2=2.10v gear actual=1st
4th: A=0.27v, B=14.05v, 3-2=1.45v gear actual=3rd.

so the A and B circuits are closing appropriatly. 3-2 is questiinable over what it's doing but I'm not sure it's relivent. Also remember that when the PCM is commanding 3rd but the trans is in first, I can move the lever into 2nd and it will shift to 2nd. When the lever is in D and the car PCM has commanded 4th, if I move the shift lever to 3rd it kicks into nuetral.

i'll try grounding the solonoids with the car off and me under it to listen for the solonoids actually cycling.