6L90 won’t shift into 4th after rebuild

TCC, PCS#4, & PCS#5 are Normally Low while Main PCS, PCS#2, & PCS#3 are Normally High....This accounts for the differing results by directly applying current, I don't really recommend doing that as the module cannot be isolated from the solenoids!!!!

You're after confirming Zero & Max flow through the mechanical part of the PC Solenoids....Not electrical testing as electrical faults will set DTC's.
I see. Can you send me a direct message when you get a chance?
 
TCC, PCS#4, & PCS#5 are Normally Low while Main PCS, PCS#2, & PCS#3 are Normally High....This accounts for the differing results by directly applying current, I don't really recommend doing that as the module cannot be isolated from the solenoids!!!!

You're after confirming Zero & Max flow through the mechanical part of the PC Solenoids....Not electrical testing as electrical faults will set DTC's.
Not great news I'm afraid. Back to confusion.

Reman Sonnax TECHM came in yesterday and I installed it this morning. I borrowed a friend's MDI and subscribed to the GM Techline Connect. I reprogrammed the TCM using SPS2 and used GDS to relearn the shift adapts. Went for a test drive and almost got stuck, had to have a buddy tow be back.

It is full of fluid, and had warmed up to 145. Backed out of the driveway just fine, drove down the road just fine, but would not shift into 3rd. Got to a stop sign and it wouldn't move at all. No reverse, no forward. We got it back to the house and let it sit for 20 minutes and it's still not working. I turned it on, no reverse or forward. Put it into park, then back into reverse and it worked just fine. Drive only worked with high RPM, and then I went back into reverse and it almost felt like the little roll that autos do when you put them in park, and then didn't want to back up.

Like I said, I programmed it using all GM stuff, it is totally full of fluid. I'm at a loss. Is this normal? I can't even get to the few rough drive cycles that people talk about when replacing TECHMs because I can't even get down the road.

The paperwork that came with the TECHM from Sonnax mentioned doing air checks with the unit installed. That didn't go super well compared to how it went before I put it back in the truck. Only 2-6 had a really solid engagement. All others were pretty soft and mostly just shot fluid out of a different hole back into my face.

Any ideas? I'm at a loss. At this point I'm almost wishing I had spent the 5 grand on a GM reman since I'm already in like $2,500 and it works just as bad as before I started!
 
This is why we test components. Stop forcing it to move....You're burning frictions!

Strange the symptoms changed with the TEHCM swap, Go back over it......The 1-2-3-4 & 4-5-6 should hold with zero leaks while air testing.

DTC's?
 
This is why we test components. Stop forcing it to move....You're burning frictions!

Strange the symptoms changed with the TEHCM swap, Go back over it......The 1-2-3-4 & 4-5-6 should hold with zero leaks while air testing.

DTC's?
Can you watch these videos and tell me what you think? I just did brand new (again) lip seals on the stator and 4/5/6 teflon rings. What else could be leaking?




 
The 3-5-R has a bleed orifice in the drum so a little leakage is normal.

I hear a little hiss air testing the 4-5-6 through the Stator but no hiss when checking directly on the Turbine Shaft.

It's possible to undersize the sealing rings if the resizing tool is on the small side, Some are so poorly made the inside diameter isn't concentric.

Let the 4-5-6 drum sit in the Stator Tube overnight/12 hours & retest, Might try some assembly lube or ATF on the rings and they're never dry in operation.

I like to lay my unit's flat, Pump a little ATF in each feed passage to help with spotting crossleaks....But I don't expect you to buy a holding fixture or manhandle the unit onto a bench.

I rewatched the first video....4-5-6 test (Once you got the air nozzle sealed) sounded pretty good.
 
The 3-5-R has a bleed orifice in the drum so a little leakage is normal.

I hear a little hiss air testing the 4-5-6 through the Stator but no hiss when checking directly on the Turbine Shaft.

It's possible to undersize the sealing rings if the resizing tool is on the small side, Some are so poorly made the inside diameter isn't concentric.

Let the 4-5-6 drum sit in the Stator Tube overnight/12 hours & retest, Might try some assembly lube or ATF on the rings and they're never dry in operation.

I like to lay my unit's flat, Pump a little ATF in each feed passage to help with spotting crossleaks....But I don't expect you to buy a holding fixture or manhandle the unit onto a bench.

I rewatched the first video....4-5-6 test (Once you got the air nozzle sealed) sounded pretty good.
During the second video I was pumping air into the 4/5/6 drum, when it was upside down on the pump, as soon as I released air the clutch pack would just like “die out” and not really hold any pressure whatsoever. Is it possible that just mis-sized teflon rings could cause such a bad leak? Or is there a chance that I have a bad stator or stator support? It just seems like a much bigger leak than even the bleed hole on 3/5/R. Any way to test the stator itself?
 
I don't have the greatest hearing after close to 30 years being a mechanic, Some frequencies I can't hear at all ;)

Get the 1-2-3-4/3-5-R drum out of the way by installing the Sun-Gear & Bearing on the Stator, Then slide the 4-5-6 drum/Turbine Shaft into the Stator Tube, May allow you to hear where the leak is.

I've had spotty luck with having the Pump Cover/Stator & Pump Body/Bellhousing machined...So 90% of my 6L80/90's get new OE parts.

What procedure did you use replacing the Stator Support Gasket?
 
I don't have the greatest hearing after close to 30 years being a mechanic, Some frequencies I can't hear at all ;)

Get the 1-2-3-4/3-5-R drum out of the way by installing the Sun-Gear & Bearing on the Stator, Then slide the 4-5-6 drum/Turbine Shaft into the Stator Tube, May allow you to hear where the leak is.

I've had spotty luck with having the Pump Cover/Stator & Pump Body/Bellhousing machined...So 90% of my 6L80/90's get new OE parts.

What procedure did you use replacing the Stator Support Gasket?
Ok, I’ll try testing without 3/5/R later today. As for the stator support gasket, I took the bolts off, pressed it out, cleaned excess gasket material, installed new gasket, pressed the support back in, and torqued bolts in the sequence.

I did just get a new paper gasket, is there a better coated one that I should have used? If so, can you link it? I also couldn’t find the O-Ring on the stator support online so I didn’t replace that, can you link that as well? Or a kit that has them both?

Might be a bit of a long shot, but do you think (going off the idea that the Amazon sizer wasn’t perfect) that I could use a blow dryer and just heat the teflon rings a little, almost like a natural heat cycle, before letting them sit inside the pump? Or would that be pointless? I know it’s a little bit janky, but I’m just trying to think if there’s any saving this without getting a whole new stator and bellhousing.
 
Drawing the Stator onto the Pump Cover with the bolts WILL damage the Pump Cover...So you did it correctly. Though I would retorque the bolts!!

The O-ring & Gasket comes in Trans-Tec & Toledo seal kits, Never tried to buy them separately. GM doesn't sell them as they're not serviceable in their eyes/opinion.

Heating the sealing rings is a good idea, I soak mine in hot water before installation & resizing to make them more pliable.

You did inspect the Stator Tube (Where the rings ride)? Not really a common issue on 6L's like on 4L60's, But a habit none the less.

Also assuming the Stator Support Bushings were replaced?
 
Drawing the Stator onto the Pump Cover with the bolts WILL damage the Pump Cover...So you did it correctly. Though I would retorque the bolts!!

The O-ring & Gasket comes in Trans-Tec & Toledo seal kits, Never tried to buy them separately. GM doesn't sell them as they're not serviceable in their eyes/opinion.

Heating the sealing rings is a good idea, I soak mine in hot water before installation & resizing to make them more pliable.

You did inspect the Stator Tube (Where the rings ride)? Not really a common issue on 6L's like on 4L60's, But a habit none the less.

Also assuming the Stator Support Bushings were replaced?


Update as of today!
 
I think once it gets warm with some ATF you'll be good.
I got the unit all back together tonight. I split the VB back apart just to make sure everything was good and the only things that seemed a little off were the two long valves in the end of the VB, clutch selector valves I believe?

They aren’t stuck, but they are snug towards the end when they are fully inserted. They move pretty free throughout the rest of the bore, when I can still hold the end, but when pushing them fully in they take a bit of force.

Is that normal? If not, any way to help it? The Sonnax zip kit didn’t come with new valves for them, just new springs.
 
The 2 Clutch Select Valves need to slid out of their bores EASILY, Should be able to tip the valve body over & the valve glide out of it's bore with nothing but gravity.

I can usually get the valves free by repetitively cleaning the Valve Body & cycling the valves it their bores.

TransGo has a set of steel clutch select valves part# 6L8 CS-TCC, Only use the clutch select valves & springs.....Not the TCC valve.
This kit.
This kit will usually solve sticky valve issues & are more tolerant of debris.
 
How much would a local shop charge to go through it if you carry it in?
Unfortunately not an option. Before I started the rebuild I called every shop around me and none of them do bench work anymore. They all wanted the whole truck, and none of them would even rebuild it. They all wanted me to bring the whole truck, and then they were just going to replace the unit. All quotes were over $7,000.
 
Unfortunately not an option. Before I started the rebuild I called every shop around me and none of them do bench work anymore. They all wanted the whole truck, and none of them would even rebuild it. They all wanted me to bring the whole truck, and then they were just going to replace the unit. All quotes were over $7,000.
They are getting a kick back from snap credit with their 35% interest rate. How much to ship it to clinebarger and back?
 
I would try an OEM valve body, just to rule out the sonnax shift kit installation.

Do you have to set the thickness of the clutch/steel packs on those?
 
Unfortunately not an option. Before I started the rebuild I called every shop around me and none of them do bench work anymore. They all wanted the whole truck, and none of them would even rebuild it. They all wanted me to bring the whole truck, and then they were just going to replace the unit. All quotes were over $7,000.
Interesting. So those shops want to use a central rebuilder, send in your transmission, give a bit for a core charge back and take delivery of an alleged “re-built” transmission with probably no options for improvements except for a bullet torque converter. :(
 
The 2 Clutch Select Valves need to slid out of their bores EASILY, Should be able to tip the valve body over & the valve glide out of it's bore with nothing but gravity.

I can usually get the valves free by repetitively cleaning the Valve Body & cycling the valves it their bores.

TransGo has a set of steel clutch select valves part# 6L8 CS-TCC, Only use the clutch select valves & springs.....Not the TCC valve.
This kit.
This kit will usually solve sticky valve issues & are more tolerant of debris.

Update as of tonight. My nightmare continues. Please watch both linked videos and let me know if you have any thoughts or questions. I appreciate all of the help despite my struggle!



 
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