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Would like to try to find out what would cause a 4l80e trans pressure to fluctuate at idle between 150 & 60 psi and when driving shifts real hard and pressure reads 150 psi seems like pressure rises too soon right of idle when pressure doesn't fluctuate and starts off about 60psi then when shifts rises to 150 psi trans works fine
First off, welcome. Next, i would go down to the CHASSIS, SUSPENSION, APPEARENCE section. Then to the Automatic Transmission section. There are plenty of guys down there that will help you. Vorteciroc is very good with theses trans. I think he may have even helped design it.
Would like to try to find out what would cause a 4l80e trans pressure to fluctuate at idle between 150 & 60 psi and when driving shifts real hard and pressure reads 150 psi seems like pressure rises too soon right of idle when pressure doesn't fluctuate and starts off about 60psi then when shifts rises to 150 psi trans works fine
Is this a completely stock 4L80E transmission?
Stock PCM and wiring?
Are you using a mechanical gauge to read line-pressure?
You are going to want to start looking at the EPC (electronic pressure control) solenoid...
You will need some type of scan-tool to compare line-pressure on your gauge with the EPC solenoid amperage being commanded by the PCM or scan-tool.
First off, welcome. Next, i would go down to the CHASSIS, SUSPENSION, APPEARENCE section. Then to the Automatic Transmission section. There are plenty of guys down there that will help you. Vorteciroc is very good with theses trans. I think he may have even helped design it.
Thanks! LOL, no...
Yes I was an Engineer on the 4L80E team... but I did not design the transmission.
I was a "Repair-Engineer" for the 4L80E team...
Meaning that I was responsible for designing corrections and new parts, that would solve problems with the original design of the 4L80E.
The people working with me, created the yearly updates and changes to the 4L80E as the years went on.
As well as "Repair-Engineers"... there were also "Design-Engineers"... They created the initial 4L80E model.
I had the "Fun-Job" of correcting all the ****-Ups that the "Design-Engineers" created! LOL!!!
Last edited by vorteciroc; Dec 25, 2020 at 02:04 AM.
Yes I was an Engineer on the 4L80E team... but I did not design the transmission.
I was a "Repair-Engineer" for the 4L80E team...
Meaning that I was responsible for designing corrections and new parts, that would solve problems with the original design of the 4L80E.
The people working with me, created the yearly updates and changes to the 4L80E as the years went on.
As well as "Repair-Engineers"... there were also "Design-Engineers"... They created the initial 4L80E model.
I had the "Fun-Job" or correcting all the ****-Ups that the "Design-Engineers" created! LOL!!!
The trans is all stock and its in a 02 gmc 3/4 ton truck I went through the trans changed all the electronics and converter due to a converter failure im using a analog gauge when cold trans works as it should and sometimes even when hot if I restart the truck it probably has a shitload of codes in it and I plan on taking it to a shop that a friend has a proper scan tool thank you for your valuable time helping me
a failed converter will put a lot of crap into the oil. when you went though the trans did you pull apart the pump? when a converter goes...wow it looks like little pebbles of **** all through the trans. if you look in the cone side of the EPC filter that'll be the tell-tale sign. little nuggets of friction material get caught in that little 60 micron filter and starves the EPC
a failed converter will put a lot of crap into the oil. when you went though the trans did you pull apart the pump? when a converter goes...wow it looks like little pebbles of **** all through the trans. if you look in the cone side of the EPC filter that'll be the tell-tale sign. little nuggets of friction material get caught in that little 60 micron filter and starves the EPC
I installed a new front pump it had trash in it and I overhauled the trans cleaned the case and all parts very well all seals clutches steel screens and electronics were replaced along with the converter and cooler and flushed out the lines I actually pulled the pan a couple of days ago and it was very clean and the fluid is clean
not to be pedantic, but when you say "new pump" did you pull it down to make sure everything was right? almost every reman pump i buy needs a bunch of work to make it serviceable. i know its annoying to have to "fix" a replacement part right out of the box but that how these things are i guess.
to me when I see funny pressure readings first thing I do is unplug the trans. does that stabilize the pressure? if yes i start looking at EPC and tune. if no I work backwards from the pressure port to the pump itself.
Hi Doug,
What do you typically find are the most common things needing to be replaced on these used pumps? The converter limit valve assembly, the TCC enable valve assembly, the TCC valve assembly just need to be taken apart and cleaned, right? Those aren't wear items, correct? I was just planning on replacing the gears, PR valve, boost valve, boost sleeve, bushings, rings and seals.
most often I find that its not just one smoking gun, but a bunch of tiny little things that bleed TCC release or apply oil until you have an issue. if you arent doing the converters yourself, you just have to trust they are putting good parts in there.
in the units i open up that have signs of TCC failure, I almost always find the bore plugs for the TCC valve are really worn. the edge of the plug look like someone used a file on it. I have a selection of o-ringed bore plugs on hand to replace these. You can get them in the sonnax sure-cure kit....which leads to the other thing i see a lot in TCC failures....the stator support bushing at the front end is worn badly. It LOOKS nice but when checked with a ID bore mic or even just against the input shaft it's really loose. This isnt just a bushing, its also a seal for the TCC release oil. The other side (inboard) of the bushing is the TCC apply oil and it's seal at the other end is the front most teflon ring for the fwd clutch apply oil. All that **** has to be really nice for the TCC circuit to have a fighting chance.
Another thing to think about is that the gear fit to the converter hub and front bushing itself is a seal for TCC oil. So if you have a shitty converter hub, that oil will bleed off right into the front drain. I thank Jake to waking me up on that one.
Thanks again Doug! I’m planning on getting a brand new converter and will make sure that I inspect all the pump components and replace what is needed. This is why I asked, so that I have all the parts on hand when I start taking the pump apart.
I see that the Sonnax Sure cure kit comes with the following for replacing the TCC Valve Bore & Pressure Regulator Valve Bore end plugs
• End Plug, Large, .668" dia.
• End Plug, Medium, .625" dia., (2)
• End Plug, Small, .500" dia.
• O-Ring, Large
• O-Ring, Medium (2)
• O-Ring, Small
I only need the plugs and the o-rings in that kit so I'm looking to source those separately but it looks like OEM are just plugs with no o-rings on them? Are the sonnax ones grooved then for an o-ring to fit?
For a 2005 4L80E I'm seeing that the TCC valve bore plug on the bottom #222 in the diagram, The Pressure Regulator Plug #232, and Converter Limit Valve Bore Plug #212 are all GM part 24243484. It looks like one of them comes in the S34165E kit to replace #232.
The TCC valve bore plug #225 in the diagram is shown as 8682857
#222 can also be a large plug depending on the year, but I'm not sure what the part number is on that. Is the 2005 year the medium sized plug? Note sure which years had the larger sized plug or the part number. Perhaps the part number is #8682855 for the larger one?
#212 can also be .275" wide or .177" wide depending on the year. Do you know when they made the change over?
Also not sure what's up with the Sonnax instructions saying that if #212 is the 0.275" wide to leave it as is and only replace it if the OEM plug is .177" wide....
Last edited by 5.7stroker; Dec 26, 2020 at 04:50 PM.
i buy a lot of that stuff from transpartswarehouse dot com, however sonnax only sells those bore plugs in packs of 5....soooo the kit becomes pretty useful
Took the pump that is out of my 2005 core and measured some end plugs. Time to clean with solvent and get the air gun out. Measurements listed in the image beside each plug below.
Since #225 in post 9 above (TCC plug at the top in the image below) is close to a width of 0.275", the Sonnax 4994-13 is a 0.177" cannot be used. A new OEM part plug that has no o-ring will be used. Part #8682857
#222 in post 9 above (TCC plug at the bottom in the image below) will be replaced with Sonnax O-ring plug 34200-05K which fits 0.625" dia
#212 in post 9 above (Converter limit plug in the image below) will be replaced with Sonnax O-ring plug 34994-14K which fits 0.668" dia
#232 in post 9 above (Pressure regulator plug in the image below) will be replaced with Sonnax O-ring plug 34200-05K which fits 0.625" dia
Also noticed that there can be a lube hole on the separator plate or not be a lube hole depending on if the core is 97 and newer or not.
These plugs are not critical in the same way the VB end plugs are for say a 4l60e.
If you look at the placement of them, you'll see that slight leaks aren't a huge deal. If the end plug on the PR valve leaks a bit. That location is orificed, and is working only on the backside of the PR. So if there is some leak at the endplug, your result will be line pressure that is slightly higher.
The TCC clutch shift valve, with the converter locked, the area captured with that plug is exhausted anyway...so leaks don't matter
and when unlocked, it just sees oil that dead-heads as part of a longer circuit, and that oil ends up being front lube and TCC release side oil...so some leaks there *could* be bad...but if you're properly feeding the circuit via line to lube, there will be plenty of volume to never notice an issue
Now, with all that said, there is not any downside to using these O ring end plugs and being sure there are no leaks. Use em if you've got em.
for those of you on a serious budget that don't want to spend the money on the o ring versions, you can take a pipe cutter. The type used for copper pipe and plumbing. And just "score" a ring into the endplug.
What you're doing is ever so slightly raising the material on either side of the cutter.
Once you've scored your ring, you will have to gently *tap* the end plug into place. This is because the raised material is tight on the bore. This will seal any leak there may have been.
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4l80e trans pressure fluctuates 
LOL, no...
