• Welcome to The Truck Stop! We see you haven't REGISTERED yet.

    Your truck knowledge is missing!
    • Registration is FREE , all we need is your birthday and email. (We don't share ANY data with ANYONE)
    • We have tons of knowledge here for your diesel truck!
    • Post your own topics and reply to existing threads to help others out!
    • NO ADS! The site is fully functional and ad free!
    CLICK HERE TO REGISTER!

    Problems registering? Click here to contact us!

    Already registered, but need a PASSWORD RESET? CLICK HERE TO RESET YOUR PASSWORD!

4L80E Harsh shifting from 1st to 2nd

ak diesel driver said:
Need to look at the pickups or tone wheel to see if the signal source could be swapped ie the cps would need half
as many
Click to expand...
Just brain storming here... most distributor pickups for a v8 gasser have 8 lobes, one for each cylinder to send signal to fire the coil plus give rpm signal to a tach. iirc though I might me totally wrong here, doesn't the 6.5 tone wheel on the snout of the crank have 4 lobes for the CPS? maybe, just maybe the oil pump drive cam sensor was build the same as the gasser distributor pickup coil. I was never able to get any kind of signal from the oil pump drive sensor on mine plus it was puking oil from the connector. not sure if it's a candidate to be dissected.
 
Well. I’m back at it again. I have been doing a lot of reading on the differences in 4l80e’s Mainly from this thread here.

4l80e and the differences between years

Need some help. I bought a 1999 chevy k2500. The 90s bodystyle but the transmission is out. What model year transmissions will drop in and work? I have been told that only 99 and 2000 will work but that just doesnt quite sound right to me. So if you could please clarify for me that would be great.
www.thetruckstop.us

rather than shelling out $100 for a new ECP solenoid I have the opportunity to pull one from a working trans in that 03 express van box truck my buddy has which has a bad engine. Today I dropped the pan on it and have the EPC from it to try, before I order a new one.

After removing, inspecting, and ohm testing this solenoid (ohmed out within spec). I discovered this 03 trans calls for a different solenoid, looks exactly the same other than the connector. From what I can tell, GM just changed the connector and upgraded the internal harness after 03, but it all still works the same.

I have a re-useable pan gasket and thinking about trying this one in the 93’s trans tomorrow, I found a pigtail in a stash of old harnesses that will work on the solenoid where I can make it work without changing the internal harness. Plan is to drain the fluid into a clean container since the pan has a drain plug, swap in the solenoid while inspecting the innards (pan debris and whatnot). Supposedly this trans was rebuilt back in 2018 and only had about 2k on it when I bought the truck, that makes it now having only 6k miles since it’s rebuild 7 years ago. Not planning on replacing the filter or fluid for this test unless I find things that would force me to do so.

I’m hoping this will fix the issue, but at least rule out a trans issue vs the EZ-TCU as the problem.

If this works, I will order the new parts along with new filter and fresh fluid. I will try to post an update on it sometime late tomorrow or Sunday.
 
Welp. Got the EPC solenoid swapped out this morning. Refilled with fluid. Took the truck out for a short test drive to warm up the trans. As it only acts up when warm. At first it started shifting a little harsh but it seems like it has softened up some. Drove out to my daughter’s house about 5 miles away and it seemed fine. I’ll be working out here for a while today so hopefully later on this afternoon I can go for a longer drive to see if this has actually helped anything.

When I dropped the pan. All seemed good. No debris in the pan. Magnet has a little bit of muck and the fluid was somewhat dark red but clean. Moving forward if this works, I’ll order the new part and then do a fluid and filter then.
 
Oh yeah and while inspecting the EPC that was in this trans, there’s no GM part number or any other markings on it anywhere like there was on the donor one. I think it’s an aftermarket part
 
Well I was able to go for a longer drive this evening and I’m torn about this solenoid being the fix. I will admit it is shifting better and not as harsh as it was, but being the fact that I have all the setting in the EZ-TCU for the softest shift possible, I’m not convinced the EPC is the only issue.

I wish there was more controllability and more options on the live data from this controller to help diagnose this. One thing I can do it go back into the settings and set it for firm shifting and see if anything changes, before when I tried this, nothing changed. I’m almost thinking about trying to find a different trans controller. When I had the pan off I did conclude that the factory TCM that’s in the truck will not work since the valve body is for a newer 94+ trans and not for a 93. What I don’t know is if an eeprom chip for a newer GM TCM will allow it to work. Maybe if I can find a newer van TCM on the flea bay since I should be able to use the factory harness with it. IDK. If I. Went that way I would also need a way to read data and codes too, don’t have the funds to invest into a tech 2!


anyway since my finding what looks like a “no name” EPC solenoid in it (no markings what so ever on it). Chances are the other shift solenoids are also of unknown origin too! I might as well look into replacing them all with GM parts. This way I can be sure to eliminate that as an issue.
 
Ya know the funniest thing happened last night leaving my daughter’s house heading home! Of course the truck had cooled off being parked for a while but I couldn’t even feel the darn thing shifting at all driving home!!!

That was its third drive since swapping in that other EPC so I think I just need to drive it more and see what happens!
 
Doug
There is a reason why your transmission is shifting as hard as it is. The computer might be doing it to protect the clutches.
 
dbrannon79 said:
Back probing pins C and D on the trans connector revealed 11-12 volts with the key on. if disconnecting the connector allows the trans to run at full pressure (no voltage to the solenoid) then I would assume when voltage is applied it should lower line pressure.

Looking up the EPC online, there not a cheap replacement, the GM one is a little over $200. I want to make sure this is the issue before tearing into it.
Click to expand...
You are right. No voltage means highest line pressure. The TCM controls that function through variable width to the force motor pressure control solenoid. Higher voltage means less pressure to the clutches. Think of it as a safety mechanism to prevent clutch slippage. Now find out why the TCM is doing this. One of the most common causes is the torque converter clutch slippage.
 
dbrannon79 said:
Well after all the work that went into fitting a factory TPS on the truck and seeing that it reaches 5v before a full sweep of the throttle at WOT I have found out the trans is shifting harder than before I started. before I drop the pan and attack the PCS I need to go back to the drawing board on this TPS. need to find something that doesn't reach 5v until the throttle is at WOT and will rest at about 0.5v at idle.

yesterday I did check the cable operated TPS with my meter and it does work at full sweep but the cable only has about 2 inches of travel where I need more to allow the IP to do a full sweep. That or a shorter arm on the throttle shaft. I pulled the box apart on it and see that I could change the spring so it doesn't add to the pedal return resistance. If I can come up with a shorter arm for the shaft I can make it work.

Once I figure this out and resolve TPS issues, then I can dive into the trans.
Click to expand...
TPS is the best place to start. Proper adjustment using a test block gage .646.
 
@GenBiltstein The TCU is an aftermarket EZ-TCI TCU which I have not been able to get much information from the mfg unfortunately. and very limited data from it on the display.

The only fail safe the TCU has is if it detects an issue it will go into limp mode and stay in 2nd gear. it shows no faults. the main issue I believe is it doesn't have the ability to read what the EPC is doing, only send commands.
 
dbrannon79 said:
@GenBiltstein The TCU is an aftermarket EZ-TCI TCU which I have not been able to get much information from the mfg unfortunately. and very limited data from it on the display.

The only fail safe the TCU has is if it detects an issue it will go into limp mode and stay in 2nd gear. it shows no faults. the main issue I believe is it doesn't have the ability to read what the EPC is doing, only send commands.
Click to expand...
Just what is the EPC?
 
dbrannon79 said:
Well after all the work that went into fitting a factory TPS on the truck and seeing that it reaches 5v before a full sweep of the throttle at WOT I have found out the trans is shifting harder than before I started. before I drop the pan and attack the PCS I need to go back to the drawing board on this TPS. need to find something that doesn't reach 5v until the throttle is at WOT and will rest at about 0.5v at idle.

yesterday I did check the cable operated TPS with my meter and it does work at full sweep but the cable only has about 2 inches of travel where I need more to allow the IP to do a full sweep. That or a shorter arm on the throttle shaft. I pulled the box apart on it and see that I could change the spring so it doesn't add to the pedal return resistance. If I can come up with a shorter arm for the shaft I can make it work.

Once I figure this out and resolve TPS issues, then I can dive into the trans.
Click to expand...
Retrieve DTCs and make sure that you are not getting one of those DTC 21 or DTC 22. TPS low or high voltage.
 
GenBiltstein said:
Just what is the EPC?
Click to expand...
EPC = Electronic Pressure Control. other names for it is a PCS = pressure control solenoid.

GenBiltstein said:
Retrieve DTCs and make sure that you are not getting one of those DTC 21 or DTC 22. TPS low or high voltage.
Click to expand...
the TCM is not GM.

www.tciauto.com

TCI EZ-TCU GM Overdrive Transmission Controller Kit

Maximum control over shift points, shift firmness and shift speed. No software, laptop or experience needed. Completely intuitive programming interface or optional fully programmable based on load, speed and RPM
www.tciauto.com www.tciauto.com
 
Just wanted to post an update since the weekend. so far after swapping in the EPC solenoid from the donor, the truck has been shifting perfectly fine.

I've got my parts list together to order the new solenoid, pan gasket and new fluid/filter. I will continue to drive it a few days longer before I conclude this was the fix though.
 
You must log in or register to reply here.
Back
Top