Hey I was doing some more looking on a 4l60e I�m having issues with and I put a pressure gauge on it and I�m getting pretty constant 90psi in all forward gears and 140psi In reverse at idle. pressure will not increase though. Stays at 90psi no matter 1 2 3 or 4. I�m thinking that might be an internal leak or more likely the boost valve being stuck. Unplugging the trans connector does not change anything. Still 90psi. Fluid was at full level, tried overfilling by about a 3/4 quart, no change. Any ideas before I pull the pan?

Is this on a 200K vehicle or a fresh rebuild?
If you look on a scan tool you can see desired PC solenoids amp & actual amps. They should agree if they do not chances are you have a bad PC solenoid. Some scan tools will let you adjust the amps up & down as a test. You should be able to watch your pressure gauge go up and down with the command. if it doesn't replace it and retest to see if pressure now changes.

The issue could be in the wiring or the PCM itself too. Un-plugging the case connector and not getting any pressure rise is most likely an internal issue.

If this is a fresh rebuild... I had a customer that rebuilt his own and experienced a similar issue. He brought me the whole unit and he had placed the PC solenoid clip in the wrong cavity.

it is a fresh rebuild. I have a guy with a tuner that I will have access to tomorrow and be able to mess with the epc values. I�m just trying to find out what is responsible for the pressure increase. Certain the pc solenoid is in the right spot. I pulled the pan and there didn�t appear to be any obvious internal leaks, pc solenoid had a little gunk on it though(not enough to clog the screen but visible). I�m going to brake clean it and stick it back in. Pulling the pc valve in the pump tomorrow and checking it out as well. To add a little more context too, old converter was used and trans got contaminated a bit. Worked until filter got clogged up and I swapped the converter for a new one and flushed the trans. I don�t really see any screens getting clogged cause this because I would think that there would still be a pressure fluctuation, but there�s nothing, just constant 90psi.

The clip I'm talking about cannot be seen with out removing the valve-body.
Here is a GM PC solenoid function guide

Anytime I have seen this , The PCS was bad even a couple new ones, If you have not swapped that then I would do that before anything else.

Checking to see if this problem was resolved? Having similar issue with my daughter's blazer, I'd rebuilt it 37k miles ago and it started flaring on 2-3 shift last week. Was only hitting 64ish psi. Pulled pan, 0 clutch material, fluid wasn't burned, installed transgo shift improver, aluminum pistons, pc solenoid, and .500" boost valve. Now I'm up to 90psi but won't go any higher.

+
Usually if it's not the PCS of course if possible verify the current change up and down by data logging to eliminate outside cause.
But internally
MISSING OR DAMAGED SCREEN IN PUMP OR ITS ORING.

STUCK PUMP SLIDE, IF THE PUMP SLIDE MOVES OVER TO MAX POSITION AGAINST THE SLIDE SPRING THE PUMP WILL SIMPLY BE TOO SMALL.THIS IS NOT COMMON USSUALLY ONLY HAPPENS WITH MACHINED PUMP WHERE THE SLIDE HEIGHT WAS NOT MEASUERED TO PROPER HEIGHT
.
BROKEN PUMP SLIDE SPRING

AFL VALVE STUCK OR LEAKING BADLY

PCS SCREEN BLOCKED OR COLLAPSED IN VALVE BODY PLATE

THE TWO SEALS PEICES FOR THE SLIDE REVERSED DURING ASSEMBLY WITH THE RUBBER STICK OUTBOUND INSTEAD OF THE TEFLON, IN THIS CASE WILL WORK OK FOR A WHILE THEN LOOSE SEAL CAUSING MASSIVE LEAK

MISSING OR BORKEN PUMP RING IN ROTOR ASSEMBLY, YES, I HAVE SEEN A FUNCTIONING PUMP WITH THIS IT WILL WORK BUT HAS PERPETUAL LOW PRESURE

OPPS sorry for all caps i hit the caps button but not going to retype all. Others may chime in with more but off hand that is all I can think of right now.

Thank you very much for the reply and Happy Thanksgiving!

I'd datalogged watching actual and reference current while eyeing pressure gauge, after .7A it wouldn't rise over 90psi no matter throttle position. I'd pulled the valve body / AFL when installing the shift improver kit, screens were clean but pcs had a small amount on it like OP above. I'm thinking it's in the pump but was hoping I was wrong and was missing something. It was rock solid up until daughter noticed the flare. Thank you again!

This comment is NOT directed towards anyone, NOT the OP, NOT anyone Replying... NO ONE!!!


I love how People will want an answer to a Question, But ONLY look so Far...
Essentially they get an answer, but there is NO understanding of the Answer...
Again, (Not trying to be overly reductive) Essentially they "Learned" the Answer, but in actuality, they did NOT "Learn" the Answer.


Lets go back to a time when I would have (on a rare occasion) given a lecture at a GM Training Seminar.
I would ask a room of People a Question (Technicians, Managers, Executives, Professors, Service Advisors, Engineers, Students training to become Technicians, Etc).
I asked: "What does the 4L60E EPC Solenoid do?"

Generally, I would most always get the same Answer: "Sir; It's right in the Name... It Electronically Controls Pressure".
I would then address everyone again, and say: "Yes, but Please be more specific in your answers, I am not looking for elementary responses".

Eventually...
I would get the following Answer: "The EPC Solenoid increases Line-Pressure"
.
.
.
.
.
.
.
.
.
Then, I would stand silent and not state whether or not the Given Answer was Correct or Not.
I would stay silent and just wait...
Everyone would just silently stare at me in suspense.

Finally, I would reply with a simple, calm, quiet: "Uumngh.............. Relative to what?"
"Otherwise I really must say No, that is actually Incorrect".

Everyone would then all be looking at one another in confusion...
I would then say: "Someone please provide us with an example of the EPC Solenoid's Operation".

...AND...
Most of the time someone would say: "The Solenoid uses electricity to increase the Line-Pressure".



No.

To put things into perspective.
The Oil Pump will build the Line-Pressure...
It is the EPC Solenoid's Job to LOWER the Line-Pressure.
It uses electricity to EXHAUST Line-Pressure.

Why does the EPC Solenoid work this way/ Why was it designed in such a manor???
It is a Fail-Safe...
If there is no Power to the Transmission, or the EPC Solenoid becomes Inoperable...
Most of the time, the Transmission should have FULL Line-Pressure, instead of the Opposite and have NONE!

Most of the time, with a mechanically sound Transmission, Unplugging the Main Electrical Connector from the Transmission will result in FULL Line-Pressure.
If Debris is stuck in the EPC Solenoid, and the Solenoid can not Close/ go to it's Resting Position...
Line-Pressure will be at least partially Exhausted regardless of Electrical influence.


I hope someone learned something,
Thank you.

As always, very good explanation on the operation of how these systems were designed and work! Learned something new.

Thanks for your post!

Always look forward to your replies and comments .