Fixed:Everyone’s fav topic: 6l80 issues

[Starkworks]

2020 Chevy Suburban w/ 110,000 miles

Before tear down issues: progressive slipping/flares from drive. Noticed predominantly after driving for a period of time and warmed up. Able to engage and drive after a period of cool down. A code finally popped up with a p2723. Lost all gears, including reverse. I had to have the truck towed home.

During tear down:
- metallic dust in the pan. Assuming torque converter failure, I proceeded with a complete tear down.
- Pulled apart the valve body. No check balls in appeared to be shrunken or stuck. The valves appeared to be free moving and no excessive wear on any of them.
- TEHCM: all TFP switches were intact.
- Disassembled Stator Pump: slight scarring on the pump body side and pump cover surface.
- 1-2-3-4/3-5-R housing, friction and steels looked good. Pistons good. Bearing no abnormal wear. O rings intact. No apparent cracks in weld.
- 4-5-6 housing, friction and steels were burned up. Piston looked intact. No cracks in housing though.
- center support and components looked good.
- 1-2-3-4 clutch hub looked good
- 2-6/3-5-R clutch hub looked good
- Rear carrier was intact and all gears were freely spinning.
- output carrier was fine.

Assembly:
- valve body: cleaned and installed transgo kit with new check balls. Vacuum checked all valves.
- TEHCM: cleaned and changed orange pressure switch covers and seals. All continuity testing was good.
- Stator pump: buffed out the slight scarring. Installed transgo valve kit. New seals. Reused other components. Installed new gasket.
- kept all bearings throughout as they didn’t have any scarring and thrust bearings moved easily. Nothing appeared out of place.
- replaced all frictions and reused metals in all but the 4-5-6. Replaced 4-5-6 metals and frictions.
- 4-5-6: new pistons, frictions and steels. New Teflon. Pressure checked on stator.
- 1-2-3-4/3-5-R: new frictions and pistons. New O rings. I did not specifically test for leaks as I heard that the welds are improved in the newer 6L80s. But, I did place on stator and test. No leaks that I could tell. Stator kept pressure as well.
- 2-6: new frictions
- low and reverse: new frictions
- center support: pressure test was good
- lubed everything up

After assembly:
- refilled with dexron VI
- started the truck up and have reverse. Drive works, but doesn’t shift. Flares at about 5 mph
- checked manual mode:
- 1st flares around 5
- 2nd feels like it’s binding? When in second truck doesn’t move at all and feels stuck.
- 3-6 flare around 5.
- hooked an autel scanner up and solenoids and switches appear to be working in the mode they are supposed to.
- went ahead and ordered a TEHCM, but will wait to install until I can rule of everything else.
- thermostat bypass
- reman converter

No clue what to try from here. I am an amateur at this but love learning about these transmissions! Watched quite a many hours of @NickTransmissions, which has been a huge help.

 

[swathdiver]

We'll probably hear from Nick tomorrow. Any codes since you put it back together?

 

[Starkworks]

We'll probably hear from Nick tomorrow. Any codes since you put it back together?

No, not since the code was cleared. Afraid I will blow the TM up trying to produce a code.

 

[Joseph Garcia]

Is Nick aware that he is needed here for his input? @NickTransmissions

 

[NickTransmissions]

2020 Chevy Suburban w/ 110,000 miles

No clue what to try from here. I am an amateur at this but love learning about these transmissions! Watched quite a many hours of @NickTransmissions, which has been a huge help.

Good on you for attempting the rebuild, many wont for a variety of reasons. A few questions:

1. Did you perform a fast relearn prior to your test drive?

2. What were your clutch clearances for all clutch packs

3. Did you replace the stator-to-stator support gasket?
3A. If yes to Q3, did you follow the prescribed torquing sequence?

4. Did you machine the pump body/bell housing?
4A. If yes to Q4, what was the rotor/slide to deck clearance?

5. Did you replace all bushings?

6. Did you conduct any vacuum testing on the valve body and pump valve trains?

I'll prob have more questions depending on how you answer these but your responses (hopefully) will give us something to go on...

 

[Starkworks]

Thanks, @NickTransmissions Answers below

Good on you for attempting the rebuild, many wont for a variety of reasons. A few questions:

1. Did you perform a fast relearn prior to your test drive? Not exactly sure I did. I see the option in my Autel and select it, but it doesn’t have me go through the process.

2. What were your clutch clearances for all clutch packs. Shame on me, but I didn’t check. Assumed I was using the same thickness as OEM.

3. Did you replace the stator-to-stator support gasket? Yes, replaced that gasket.
3A. If yes to Q3, did you follow the prescribed torquing sequence? Yes, followed the torque sequence.

4. Did you machine the pump body/bell housing? Not technically. I buffed the slight scarring out on both.
4A. If yes to Q4, what was the rotor/slide to deck clearance?

5. Did you replace all bushings? No

6. Did you conduct any vacuum testing on the valve body and pump valve trains? Valve body, yes. Pump, no.

I'll prob have more questions depending on how you answer these but your responses (hopefully) will give us something to go on...

 

[NickTransmissions]

@Starkworks - Conduct a successful fast adapt relearn and take it for another test drive - that by itself may solve all the issues. If you do have to pull it back out and apart, do the following:

1. Replace all the bushings - do not reuse bushings in these transmissions, especially the pump stator and body bushings

2. Vacuum test the pump (not sure why you didn't test the pump with the valve body but you don't want to omit that step - this video will show you specifically how to do it and what your readings should look like)

3. Record and share your clutch clearances, pump rotor/slide-to-deck clearance and end play measurement - this is one of the most critical aspects of any build and one of the most common things I see w/DIY builds is folks not recording clutch clearances and end play measurements
- If your clearances are too tight, you will have partial tie-ups/bind-ups upon shifting - these, like all clutch-to-clutch transmissions, are sensitive to clearances

4. Air check all applied elements to confirm everything is working as it should

5. Take pictures as you go - don't skimp on this step as they may help you after the fact - ask me how I know!

6. If all of the above is done and you still have the same problems, replace the TEHCM - a brand new one from General Motors will run ~$1,050 plus core and programming.
- Sonnax reman TEHCMs are $550-$600 plus core and programming
- Street Smart Transmissions remans are $550-$650 w/programming (you give them your VIN so they program it to your vehicle)

 

[Starkworks]

Roger that @NickTransmissions

Looks like rookie mistakes all around. Let me see if I can get this Autel to cooperate.

@Starkworks - Conduct a successful fast adapt relearn and take it for another test drive - that by itself may solve all the issues. If you do have to pull it back out and apart, do the following:

1. Replace all the bushings - do not reuse bushings in these transmissions, especially the pump stator and body bushings

2. Vacuum test the pump (not sure why you didn't test the pump with the valve body but you don't want to omit that step - this video will show you specifically how to do it and what your readings should look like)

3. Record and share your clutch clearances, pump rotor/slide-to-deck clearance and end play measurement - this is one of the most critical aspects of any build and one of the most common things I see w/DIY builds is folks not recording clutch clearances and end play measurements
- If your clearances are too tight, you will have partial tie-ups/bind-ups upon shifting - these, like all clutch-to-clutch transmissions, are sensitive to clearances

4. Air check all applied elements to confirm everything is working as it should

5. Take pictures as you go - don't skimp on this step as they may help you after the fact - ask me how I know!

6. If all of the above is done and you still have the same problems, replace the TEHCM - a brand new one from General Motors will run ~$1,050 plus core and programming.
- Sonnax reman TEHCMs are $550-$600 plus core and programming
- Street Smart Transmissions remans are $550-$650 w/programming (you give them your VIN so they program it to your vehicle)

 

[NickTransmissions]

Roger that @NickTransmissions

Looks like rookie mistakes all around. Let me see if I can get this Autel to cooperate.

No worries - we were all rookies at one point and I have made my fair share of them.

Let us know the results of the fast adapt relearn...Also, if you don't already have it, download the ATSG manual from my 6L80 Information Thread, page 1 - first post: https://www.tahoeyukonforum.com/threads/gm-6l80-transmission-information-thread.141927/

 

[Starkworks]

Well, looks like this Autel doesn’t have the relearn on it. I could have sworn this one had it. Returning and getting another.

No worries - we were all rookies at one point and I have made my fair share of them.

Let us know the results of the fast adapt relearn...Also, if you don't already have it, download the ATSG manual from my 6L80 Information Thread, page 1 - first post: https://www.tahoeyukonforum.com/threads/gm-6l80-transmission-information-thread.141927/

 

[Starkworks]

@NickTransmissions - I am beginning to wonder if GM removed the fast adapt learn from the 6L80. Tried another Autel scanner, the MaxiSys MS906 Pro. It doesn’t have the selection either.

 

[NickTransmissions]

@NickTransmissions - I am beginning to wonder if GM removed the fast adapt learn from the 6L80. Tried another Autel scanner, the MaxiSys MS906 Pro. It doesn’t have the selection either.

That screenshot of the scanner showing "line pressure reset" (or something like that) was likely the function you need. Call Autel tomorrow to confirm/deny tomorrow..

 

[Starkworks]

That screenshot of the scanner showing "line pressure reset" (or something like that) was likely the function you need. Call Autel tomorrow to confirm/deny tomorrow..

@NickTransmissions - I thought so too. It doesn’t have the car go through the test. I’ll call to confirm.

 

[Starkworks]

@Starkworks - Conduct a successful fast adapt relearn and take it for another test drive - that by itself may solve all the issues. If you do have to pull it back out and apart, do the following:

1. Replace all the bushings - do not reuse bushings in these transmissions, especially the pump stator and body bushings

2. Vacuum test the pump (not sure why you didn't test the pump with the valve body but you don't want to omit that step - this video will show you specifically how to do it and what your readings should look like)

3. Record and share your clutch clearances, pump rotor/slide-to-deck clearance and end play measurement - this is one of the most critical aspects of any build and one of the most common things I see w/DIY builds is folks not recording clutch clearances and end play measurements
- If your clearances are too tight, you will have partial tie-ups/bind-ups upon shifting - these, like all clutch-to-clutch transmissions, are sensitive to clearances

4. Air check all applied elements to confirm everything is working as it should

5. Take pictures as you go - don't skimp on this step as they may help you after the fact - ask me how I know!

6. If all of the above is done and you still have the same problems, replace the TEHCM - a brand new one from General Motors will run ~$1,050 plus core and programming.
- Sonnax reman TEHCMs are $550-$600 plus core and programming
- Street Smart Transmissions remans are $550-$650 w/programming (you give them your VIN so they program it to your vehicle)

@NickTransmissions.

I contacted Autel on 1/22. They said the device I have should have the fast learn ability. Tech had to escalate to software engineers across the pacific. Due to national holiday a response won’t happen for at least 14 days per Autel.

So while waiting, I decided to tear back into the transmission.

1. Replaced all the bearings.
2. Vacuum tested the pump, results below:

• TCC Control valve: 23
• Boost Assembly: 25
• PR Valve: 24
• CL Valve: 24

3. Working on clutch clearances with a dial indicator, will report back later today. Checked with feeler gauges

• 1234: 0.072
• 35R: 0.053
• 2-6: pending…clutches move, but the backing plate doesn’t jump very much. Wave plate pushing up?
• LR pack: 0.074
• 456 will check with dial
• Will measure end play as well

4. Pump clearances:
Slide to Deck:

• 0.015

Rotor to Deck

• 0.04

5. Will air check as well

---

 

[NickTransmissions]

@starworks,

Confirm the rotor-deck is .004? If so, it's high; needs to be .002 max.

Measure the 2-6 clutch with a dial indicator. Simply lift the clutch pack up against the snap ring and record the measurement. Do this at three different points but not where the clutch snap ring ends meet (reading will be higher simply due to gap at that location). Average the three readings, that is your clearance.

Did you calibrate your vacuum tester prior to gathering the above results?

Did you test the valve trains when they were dry or did you assemble them with trans fluid or WD40 then test?

Readings of 14-21 Hg is what id prefer to see on all working valves; 23-25 Hg may indicate binding due to being too tight in the bore.

You replaced the bearings? How about the bushings - did you replace those as well?

 

[Starkworks]

@starworks,

Confirm the rotor-deck is .004? If so, it's high; needs to be .002 max.

Measure the 2-6 clutch with a dial indicator. Simply lift the clutch pack up against the snap ring and record the measurement. Do this at three different points but not where the clutch snap ring ends meet (reading will be higher simply due to gap at that location). Average the three readings, that is your clearance.

Did you calibrate your vacuum tester prior to gathering the above results?

Did you test the valve trains when they were dry or did you assemble them with trans fluid or WD40 then test?

Readings of 14-21 Hg is what id prefer to see on all working valves; 23-25 Hg may indicate binding due to being too tight in the bore.

You replaced the bearings? How about the bushings - did you replace those as well?

@NickTransmissions

Rotor to deck is 0.004. Just sits below the slide. Could the bushing be just bit low?see pic.

2-6 has about 0.050 clearance.

Vacuum was calibrated last night and again today. Still getting same readings. Valves are wet with WD40.

Sorry bushing were installed, not bearings.

 

[NickTransmissions]

@NickTransmissions

Rotor to deck is 0.004. Just sits below the slide. Could the bushing be just bit low?see pic.

2-6 has about 0.050 clearance.

Vacuum was calibrated last night and again today. Still getting same readings. Valves are wet with WD40.

Sorry bushing were installed, not bearings.

.004 is over twice the max specified clearance (.0015-.002). Have the pump machined to obtain proper clearance or look for a thicker rotor.

Bushing looks fine in those pics but they're a bit dark/grainy. As long as the hub's journal slides through it, spins freely with little to no side play and it's positioned as it appears to be, you should be fine.

 

[Starkworks]

.004 is over twice the max specified clearance (.0015-.002). Have the pump machined to obtain proper clearance or look for a thicker rotor.

Bushing looks fine in those pics but they're a bit dark/grainy. As long as the hub's journal slides through it, spins freely with little to no side play and it's positioned as it appears to be, you should be fine.

@NickTransmissions just to make sure I am still going down the right path. The rotor clearance being the way it is now. Could that be causing the symptoms in my original post? I am going to go ahead and replace the tehcm still.

 

[NickTransmissions]

@NickTransmissions just to make sure I am still going down the right path. The rotor clearance being the way it is now. Could that be causing the symptoms in my original post? I am going to go ahead and replace the tehcm still.

Maybe. If you're double the max clearance you likely are having erratic line pressure problems. If you correct it and the problem goes away, you have indeed found it.


Id be tempted to use the orig tehcm just to see if your symptoms resolve with a proper pump installed.

 

[Starkworks]

Maybe. If you're double the max clearance you likely are having erratic line pressure problems. If you correct it and the problem goes away, you have indeed found it.


Id be tempted to use the orig tehcm just to see if your symptoms resolve with a proper pump installed.

@NickTransmissions

Well, tore into back into it. New tehcm and valve body from street smart. New bell housing and pump from GM.

Still have the exact same issues.

Unable to get a response from Autel, so looking for someone local to reprogram.

May just take it to the shop as I am at a loss.