4L80E fresh rebuild, no reverse.

Before I remove the 4L80E to verify the pump pressure regulator valve is not obstructed, I'm looking to verify the NEW B solenoid is not stuck open.

Anyone with a proven method to test (besides the continuity test), which they both passed?
How do you test the solenoid valve is actually not stuck open on a new GM Solenoid?
What is the test procedure to verify the electrical circuit from the Compushift 2, is actually sending the signal to the transmission connector to the solenoid?

Have the pin-out diagram for the connector from the TCM.
Re-pinned it myself and verified it with 3 service and repair manuals.
The inner harness was sealed with 3M 8000 to the case and covering the harness plugs.
The external harness is not yet sealed, where I had to re-pin for my application.
Purchased the Compushift 2 for a great deal, because it was pinned for the Cadilac version of the FWD 4L80E.
The gentleman from HGM complimented me for realizing it just required a few pins to move for my version and how cheap it was as a result. The seller had no idea what he had. It was brand new never used, complete with harness and controller.

I'm not getting and codes from the head unit. The VSS, RPM, temps and TPS programming is completed without errors.
CSII is not throwing a code. The switch is showing proper gear, so the push button switch, which tested good at every pin, is working properly.

Have a lump in an A/C to 12v D/C with alligator clips I use for 12v dash and electronics testing.
However, not certain there's enough voltage to test the 4L80 solenoids using this, or if it will give me a false positive, with a click, when the plunger is still actually stuck open? Don't want to damage anything that isn't broken either.

When I pulled the transmission connector, as per the Sonnax No Reverse isolation test, my foot on the brake, with the transmission in reverse, had 60 PSI and throttle up, it only hit 180-195 psi.

The Sonnax engineer told me I should be seeing 300+ during this test.
He suggested an orifice or pressure regulator being blocked or restriction in the hydraulic circuit.

So reading hundreds of pages on GM Blogs, I found a frustrated re-builder who ripped his transmission out, before he properly tested the 2-3 solenoid for proper closing function, as per an expert advisor.

Any of you know a proven method that I can try to test the 2-3 "B" solenoid?

It would be great news to isolate an improper solenoid before dis-assemble and re-build, clean and verify zero 3rd / Reverse check balls and the center support runs for possible contamination.

My forward drum had a few sharp edges, so I cleaned them up with fine sandpaper and scrubber.
92K miles on the drum seals. All new bushings, (except for the center support).
The new center support I ordered from a well known high performance online store, was shipped with a billet piston, however my request it be machined down .040", (so the center support frictions he also sold me, would fit properly), could not be installed. I could have skinned a friction on both sides to make it work, which I have learned after the fact.

My calls to request a replacement or an answer why my request at the time of purchase, were all ignored.
So I'm out $300 and had to re-use the old center support, because I had no press fixture to replace the long bronze bushing.
It was not very worn, to be sure.
Verified the diameter.
It was within .004" of the new bushing on the HD unit he sold me.
The new bushing, most likely would have had to be polished to install, due to crush from the install anyways.

Went with new regular Teflon main shaft to forward drum seals, although I did purchase the blue over-sized set as well.
When I read they require reaming and sizing, I opted to just re-install the standard set.
It is possible my lack of experience and the actual wear was not within spec, or might have been made worse when it was mildly cleaned up by me. It was crunch time and back then I was being threatened with eviction on a daily basis.
Some of that pressure has been de-escalated, Thank God.

I'm over it and just want to get down the road with whatever I can and move on, at this point.
The damage has been done. The mining interests moving in here have taken over the population with dreams of high property re-sales and huge tax increases to force out the poor or retired locals, in our poor town.
Mass psychosis and greed have everyone thinking they are all going to get rich from the new mine.
It's really sad to watch.

There's no apartments or affordable housing anymore, in a town that was 85% both just 3 years ago.

There's a forward drum on the way, so I can replace the original, with re-manufacture unit that has been reamed and sleeved for what I hope is standard Teflon seals.
Bought this from the only re-manufacturer on eBay that states reaming and sleeve-ing on his sale page, so can be properly resolved, in my mind, as a possible point of failure; if/when I am forced to open it all back up again.

Had a crumb drop into the pump circuit, (after pressure testing everything and verifying good psi), when I opted to remove the filter bushing AFTER re-assembly of the core. Another dumb move. Probably could have been left alone, to avoid a stoopid human move. Live and learn.

When I pulled the pump and split to stater, found what I thought was the only chunk that fell down into the pump circuit. Because of time restrictions and threats of being forced to move, I moved forward with the install. The pressure of the situation caused me to move forward when the entire circuit should have been torn down, cleaned out and pressure tested again. There could have easily been another crumb stuck to assembly lube, somewhere in the pressure valve.
Said a prayer on both knees at the fixture, and closed the cover, hoping and praying for the best.

It is possible a small piece found it's way into the Sure Cure Pressure valve or the Sonnax AFL, which was reamed and installed during the re-build.

Also ordered a new Sonnax #7 check ball seat, which was not available when rebuilding the Valve body a month ago.
Just in case it is damaged or contaminated.

The #11 check ball seats were both changed using the Sonnax kit, which included new aluminum seats, the spring and the o-ring plug in the kit.

Polished all the pin orifices, so they could not cut the new o-rings and bench buddy every valve hole, except for the #7, since it was previously working and there was no replacement seat available at the time. (Probably a poor decision, forced to save any time possible).

Nobody should be forced to rebuild any transmission, under threat of eviction, after securing a hand shake deal to tool up and use the garage for a year (or two), to recoup the investment of the tolls and shop equipment, required to undertake the complexity of this process, in my humble opinion.

Very upset my surviving landlord is reneging on her husband's deal with me.

The pressure to build and leave is extraordinary, when I have never evaluated or diagnosed a fresh rebuild for errors.
The hundreds of mistakes a seasoned re-builder must have gone through, is finally sinking in.
Very much respect to you guys and girls that have suffered through the learning process!

Must be nice to have a Dyno.

It was supposed to be no pressure, learn what to do and have fun over the next year or more.
Now it's not as much fun.

Please advise.

Nicktransmissions or MattOlds do you have a clue or two for me?

Found it.

Check-ball #3.

Also found video that describes how SOME reprogram plates can cause a leak in the 3rd gear circuit when reverse in engaged.

So after checking that my separator plate my reprogramming designer supplied "IS NOT like the Jake's reprogramming design", and is in fact a standard 97' up plate,

I blocked the leak to the shift select valve as described in this video starting around 6:30:


Now my leak should be cured, with regard to the #3 and this circuit corrected.
"Make sure you follow the directions of the man who designed your reprogramming kit"...
unless they ignored this detail and expected you to find it on your own or hire a professional to fix it for you.

This would have left a major leak.

Drilled my shift plate to .093" for 2nd and 3rd.
.083 for 4th.

Found an odler-ish pdf that actually has recommendations for 500hp, 750hp and 1000hp bleed hole re-drilling suggestions.

These numbers ended up close and not as accurate as what Nicktransmissions suggested.
His suggestion is more refined for under 500HP, which is where the SBC ends up.

Would have used Nick's recommendations, had I seen them and recalled he covered shift plate drill sizes before drilling. Just not sure I had the middle size drills he suggested though.

Several in my kit were broken and missing right in between these numbers, so I'll have to buy a few more sets.

The cost effective Harbor Freight Small Black Box mini drill assortment, with numbered super small titanium coated drills, has proven to be well worth the cost.
Kinda glad I have the stubbornness to carry it around for 12 years, till I finally needed it.

The video does not state who's reprogramming kit this mini-rivet on the 3rd bleed is required for.
I matched the plate and determined after his very through explanation, my valve body could use this spot plugged.

The notes below state Jake's kit does not require to over-drill and rivet, because he seals or uses a different plate with alternate mods or circuitry. I have never used Jke's kit, so I have no idea.

Read the comments below the video posted above carefully, is my best advice, before you alter your separator plate.

The shifter valve would have leaked 10-15% or more of 3rd gear pressure into the shared reverse circuit. Especially bad while towing.

Removing the #2 Teflon seal on the center support, when reprogramming causes this mod to become a secret leak, for the DIY home re-builder.

Probably resulting in the 3rd clutches slipping, ever so slightly over time, between the A Solenoid and B solenoid being closed and shifts to 4th, when both are open.

"Blaser Builds" YouTube channel is great stuff.
https://www.youtube.com/@BlaserBuilds

The problem is remembering all the small details and which video to find them, when you need to recall them, between him and Richard from Precision Transmission:

Here's an example of the stuff that can burn you when the THM400 was hacked by another builder and needs to be fixed.


The mistakes and trouble-shooting and catching what others have done, starts to make the headache grow exponentially, when you don't have hundreds of mistakes a year under your belt, like a DIY builder, at home.

Can see why few re-builder's want to advise anyone DIY, when the mis-matched parts can be added and the nightmare mushrooms, with red neck engineering.

A screw-up is potentially included in every used case a bone yard will sell the regular man off the street.

If you know a junk yard owner, and he'll allow you to open the case before buying, and you already know what a screw up looks like, you're good.

If the one you buy cannot be opened by the guy off the street (and it looks like it has been opened), you might want to find another donor to rebuild, even if it has a proclaimed higher milage.

Nick has a great video on this exact topic.
It really hits close to home, that I was fortunate enough to find my first core as an OEM, from the better 97-up year (99).

Would have had to learn the hard way regarding someone else's screw ups, if all I could find was rebuilt and poorly modded or had mis-matched parts.

How would you know, on your first rebuild you got skunked from the start?

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My reprogramming kit did not come with the micro-rivet or instructions to block this bleed orifice.
You (the average Joe home builder) are supposed to know this from years of rebuilding with a dyno and testing.

The rest of us jet get scolded, if we ask for tech tips, after spending the money for the kit.

Used the spare rivets from the Sonnax Reverse Over-run kit for my plate mod.
Very careful to align both gaskets over the rivets added for both mods, before tightening the accumulator delete plate and the bottom gasket to the transmission case.

The micro-rivet required a .1325" drill to open up the #3 bleed hole for the .1495" rivet, before it would fit.
Sharing the same circuit during reprogramming between 3rd and reverse, and fixing the leak, helps me to learn and explore more of the hydraulics circuits more easily.

Sonnax 73840-19RV-SUB
RIVET, Aluminum Bag, 3 pieces COMP multiple items

(**Headache comes with the territory).

***************************************************

Waiting for the #7 check ball seat to arrive.

Bought the forward drum with a reamed and sleeved main shaft seal added.
It was more than I wanted to spend, however I was concerned after I cleaned up the rough edges, I might have left a slight leak in my 92K miles drum, despite adding new stock Teflon seals.

Bought the over-sized blue Teflon seals in case they need to be added, and after reading they require a ream without a sleeve, Opted not use them.

Now it seems the reamed drum might not actually be required, until after 200K miles and the bronze bushings are much further worn out than my unit is?

What do you guys think?

Tear open the pump,
rebuild the stack from scratch,
replace the forward drum with the sleeve,
Drill and tab the bottom of the case bleed holes, so they get plugged and cannot ever lose fluid in the event of a cracked adapter to the transfer case?

Or leave the holes alone, run the adapter wet,
ignore the mild wear on the forward drum for another 100-150K miles,
and leave the core assembled and move on with just the VB mods, repairs and proper check-balls?

Hope this helps somebody else out.

_______________________________________________________________________________

If you read my post above, I was out quite a bit of money buying a HD re-manufactured center support with a billet piston, that was not machined to use the parts, (as requested during the sale, that the same builder sent me). I was bummed out I could not find a tool to press out the longest of the bushings in the Center Support.
My guess is you have to earn one as a hand me down or have one machined for your press. $$$

Here's another video from the same guy (Balser Builds), with secret mods exposes where the center support I bought (and was was NOT machined, as requested.

The HD CS with Billet piston, would have required a special secret recipe of frictions and thicker darn near unobtainable thick TH400 steels, in order to avoid the wave getting stuck under a machined billet piston,causing another method to get the elusive NO REVERSE:


Even though my center support bushing had slight wear and the stock piston is NOT billet, I used the HD springs and the HD pressure plate, so the 6 pack of Kolene steels and Borg Warner clutches still had the recommended .040" between the top steel and the top clutch in my center support clutch stack.

If you read the comments under these videos, some experienced builders tell you one or two secrets, like use the OEM piston with the HD springs AND the HD spring plate, NOT the OEM spring plate with the HD springs stuffed into the OEM cage.
**(Donkey ears if you tried to rip apart the spring cage and add the HD springs. "I would NEVER do that on my first build!"-some ego-dum builder welder quote).

Had I forced using the OEM wave and had the HD piston machined, without the correct recipe of thick steels and more like 4-5 clutches, I would have gotten stuck under the notches, just like this video describes.

The notes below the video are helpful, but not exact on the recipe.

Richard from Precision mentions scraping 2 frictions on one side each and stacking them for a thin spacer?

I have yet to see the correct method to do this in a comprehensive video, which clearly defines HOW NOT to scrape or sand frictions and stack them.

If you have the tried and true method for performing this mod, it would be great to see pictures or a video of how, during supply line shortages and careful re-builder might use this method to make a custom spacer, using spare or worn friction parts. (And save money in the process).

Hope this helps out others.

Yah... No.

Same issue, no pressure with connector unplugged.
Should be 300+psi and instead it's 49 - 195 on the pedal, in reverse, foot on the brake.

Back on the bench.
Full tear down.
New forward drum with sleeve.
Pump examination for reverse valve obstruction, pressure valve obstruction, case circuit obstruction, center support failure/obstruction.

Hey nicktransmissions, how do I pull out the 3/8" cup plug inserted during the reprogram, without making a mess of things?

Bought the 1/4 NPT tap and 3/8 NPT tap, so plugs do not get used again in the center support.

Running the stock OEM center support, stock center piston, 6 pack clutches from CK and strong springs.

Did not drill the stater, because Using the Sonnax valve with the orifice and was told not to do both.

Getting close.

If it's not contamination at the reverse valve in the pump, can you assist with what might be the issue?

The ck kit eliminates the leaks at the accumulators and deletes them all, including the 5-6 check balls.

Sonnax over-run kit deletes check ball #1.

Will verify the center support seals ASAP.
The test from the center support feed hole was correct during assembly.
Everything is full of fluid now and I'm not experienced enough to discern what could be blow by or a leak with the feed orifices cross bleeding with fluid.

Preparing to examine the pump and valves for contamination.

Heading for the center support tomorrow night.

Full autopsy.

This sxxxxxxx.

On a positive note, the new Gearwrench ratcheting mm wrenches make the transfer case bolts and Converter a breeze to remove.

Full T-Case install and removal, trans removal, 1 day in, one day test and full removal.

It is getting easier the third time around with the correct tools.

Pump pics tomorrow.
The Bat Cat is very upset.
He expected to be camping by now.

He does not like transmission fluid in his living space.
It's tough keeping everything super kitty cat clean for his safety.


Paw wash is essential.

Love my son.

sorry to hear all the bad news!

I tried reading through this and watched the first video. It's over my head lol. Maybe manual swap. I get frustrated with automatic transmissions because I'm so old school and want things to shift when they should so I gravitate to manuals. I really hope you figure it our and get it fixed up because any Good hard journey deserves a good resolve