8 speed torque convertor parameters

[stan]

2015 Chevy Silverado LTZ 6.2L / 8 speed

Any chance of getting more parameters for the T87 8 speed transmission. I have a terrible shutter in the convertor and if the dealer doesn't get it fixed this time I wanted to try to fix if myself. I looked and all there is currently is lockup speed settings for the convertor. Nothing to do with pressure or desired slip.

Getting a new torque convertor next week under warranty. Darn thing shutters so bad you think your driving on rumble strips. Does it worse on the highway below 70 mph. I have to take it out of 8th gear if I'm not running on the interstate.

[powerhaulic]

If it makes you feel any better, my 600mi 2017 6.2 8spd Sierra does the same thing.........

[schpenxel]

Didn't the Escalade's have the same issue? Or maybe I made that up

[powerhaulic]

Didn't the Escalade's have the same issue? Or maybe I made that up

it is 8spd only i believe, there also have been an occasional 5.3 8spd occurances i have read, but mostly 6.2

[schpenxel]

New Escalades have the 8 speed also

[powerhaulic]

New Escalades have the 8 speed also

yes, i was agreeing with you.....not disputing

uplevel 5.3's also get 8spd, as well as all 6.2's

[stan]

New convertor, new fluid, fresh fast learn and the shutter is gone 100%. I still would like to set the desired slip to 0 in high gear if the pids ever become available. Maybe after the warranty runs out.

[1quickirocz]

They design it to slip some when it's in V4 mode to reduce normal engine vibrations felt. When in V8 mode the desired slip speed will be 0.

[SS_bnoon_SS]

My truck is in for converter replacement right now. Sucks to be on the bleeding edge sometimes. 17K miles, just got it used, didn't notice the issue until I drove it some the night I brought it home. Dealer service adviser tried to blame my "big wheels and tires" and I said "Hey, talk to your sales manager. He's the one putting these aftermarket parts on several trucks in your lot!" I can't wait to get it home and for HPT to unlock some more parameters for these trucks with 8 speeds.

[GHuggins]

Problem isn't so much the desired slip as it is the engagement in lower gears... Kill the engagement up through 5th so it only engages in 6th, 7th and 8th and you shouldn't have many more problems... Personally hoping HPT will unlock some more parameters, but not 100% sure it will fix everything... The only reason the OE does this is for fuel economy and to be honest - you won't notice much of a loss if any... In fact a good tune on the engine side will usually offset any loss and then some... The converters in these things are super thin and super small - just a design flaw...

[Higgs Boson]

That's exactly what I do, unlock the converter until overdrive and relatively light pedal.

[SS_bnoon_SS]

Mine had no issue at all with lower gears, but would cycle the apply and release repeatedly every few seconds and shudder every time. Converter update/replace is service bulletin PIP5337G updated November 16th, listed as "shake or shudder on acceleration", though I only really noticed it on steady state cruising.

[GHuggins]

PIP5337G: Shake Or Shudder On Acceleration - (Nov 16, 2016)
Subject: Shake Or Shudder On Acceleration

Models: 2015 - 2016 Cadillac Escalade, Escalade ESV built prior to 11/01/15
2015 - 2016 Chevrolet Corvette, Silverado built prior to 11/01/15
2015 - 2016 GMC Sierra, Yukon, Yukon XL built prior to 11/01/15
Equipped with 8L90 Automatic Transmission (RPOs M5U) and the 6.2L (RPOs L86 and LT1)
Note: This information does not apply to Silverado and Sierra models with the 5.3L (RPO L83).
Please refer to bulletin 16-NA-175 for all other vehicles equipped with the 8L90 automatic transmission RPO (M5U) with shudder concerns.

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This PI was superseded to add diagnostic recommendations. Please discard PIP5337F.


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The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern
Some customers may comment on any of the following conditions.

A shake and/or shudder during light throttle acceleration between 48 and 104 km/h (30 and 65 mph) steady state driving when transmission is not actively shifting gears.

A shudder feeling that may be described as driving over rumble strips or rough pavement.

A shudder feeling that is evident in both Drive and M7 mode.

Recommendation/Instructions
To ensure TCC shudder is diagnosed correctly, please drive the following schedule on a smooth road with transmission sump temperature between 50?C (122?F) - 70?C (158?F).

Important: For some road conditions, it may be required to apply the brake pedal and throttle simultaneously to stay within desired engine torque range.

Press and hold the tow-haul mode button for 5 seconds to disable grade braking to prevent downshifts during test.

Run the following tests for 3 operational modes:

A. Normal Operation (GDS2 for viewing only).

B. GDS2 Commanding TCC in Disabled Operation. (TCC Open).

C. GDS2 Commanding TCC in Enabled Operation. (TCC Locked).

TEST:

Drive the vehicle in 8th gear, V8 mode, with a transmission input speed of 1,050–1,300 rpm with (approximately 64-89 km/h (40–55 mph)) constant throttle input, and engine torque 200-375 Nm.

To confirm TCC shudder, the vibration concern must be created in normal operation (Mode A) of the test.

If the concern is gone with the torque converter clutch disabled (Mode B, TCC Open) and is gone when the torque converter clutch enabled (Mode C, TCC Locked), the vibration root cause is TCC shudder and the torque should be replaced.

If the concern is not present in Mode A, then the vibration concern is not TCC shudder.

If the concern is still present with the torque converter clutch disabled (Mode B) or with the torque converter clutch enabled (Mode C, TCC slip speed at zero), the root cause of vibration is NOT shudder.

Vibrations not identified as shudder should be further investigated using the “Vehicle Vibration Diagnosis in SI as a starting point.

The use of the PICO scope and NVH software can be used to confirm TCC shudder, Engine, Tire or Driveline component related conditions.

To confirm TCC shudder record the PICO scope data while driving the vehicle in 8th gear, in V8 mode, with a transmission input speed of 1,050–1,300 rpm At 40 to 55 MPH (64-89 km/h) at constant throttle input, and engine torque 200-375 Nm.

The disturbance will display as unknown and will be around 26 Hz at 16 to 24 mg as shown in the illustrations below if the concern is TCC shudder.

Note: If an engine 2 (E2) disturbance is noticed in the graph the engine most likely went into V4 mode.

Object ID: 4620118Click here for detailed picture of the image.

In the above illustration frequency and default view have been selected.

Object ID: 4620120Click here for detailed picture of the image.

Additionally the following should be performed as well during the torque converter replacement process.

Flush the cooler lines and cooler using DT-45096 transmission oil cooling system flush and flow test tool.

Use compressed air to remove any residual fluid from the cooler and lines.

Remove the transmission fluid pan and drain transmission fluid.

Note: If you find that the fluid is cloudy, milky, or appears to be contaminated with water or engine coolant, DO NOT proceed with below steps.

Follow Both SI Procedures for "Cooling System Leak Testing and "Engine Coolant/Water in Transmission."

Install a new transmission filter, clean pan and magnet.

Install the transmission fluid pan and refill with new transmission fluid following the fluid fill procedure in SI to obtain correct fluid level.

Note: Only DEXRON?HP Fluid should be used. The US part number for the DEXRON?HP Fluid is 19353429, P/N (19353430) in Canada.

Note: US dealers must order The DEXRON?HP fluid through your local General Motors oil distributor. Canadian dealer must order through CCA.

Important: Under certain load conditions a minor chuggle/shudder feel may be felt in the passenger compartment due to natural engine frequencies or Active Fuel Management (AFM) transitioning from 8 cylinder to 4 cylinder and back to 8 cylinder.

It may be necessary to compare the operation of the vehicle to a known good unit under the identical driving conditions as the operation may be characteristic.

In the event that the customer returns for a confirmed torque converter shudder after replacing the torque converter please follow bulletin 16-NA-175.

[GHuggins]

#16-NA-175: Shake and/or Shudder During Light Throttle Acceleration Between 48 and 104 KM/H (30 and 65 MPH) at a Steady State - (Jun 3, 2016)
Subject: Shake and/or Shudder During Light Throttle Acceleration Between 48 and 104 KM/H (30 and 65 MPH) at a Steady State


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Brand:
Model:
Model Year:
VIN Breakpoint
Engine:
Transmission:

from
to

Cadillac
Escalade Models
2016
2016
All vehicles Built after November 01, 2015
Equipped with 8L90 Automatic Transmission (RPO M5U)

Chevrolet
Silverado
2016
2016
Equipped with 5.3L or 6.2L Engine (RPOs L83, L86)

GMC
Sierra
2016
2016

GMC
Yukon Models
2016
2016


 

Involved Region or Country
North America

Condition
Some customers may comment on any of the following conditions:

•A shake and/or shudder during light throttle acceleration between 48 and 104 km/h (30 and 65 mph) steady state driving when transmission is not actively shifting gears.
•A shudder feeling that may be described as driving over rumble strips or rough pavement.
•Shudder feeling is evident in both Drive and M7 mode.


Diagnosis Instructions
To ensure TCC shudder is diagnosed correctly, please drive the following schedule on a smooth road with transmission sump temperature between 50?C (122?F) - 70?C (158?F).

Important: For some road conditions, it may be required to apply the brake pedal and throttle simultaneously to stay within desired engine torque range.

Press and hold the tow-haul mode button for 5 seconds to disable grade braking to prevent downshifts during test.

Run the following tests for 3 operational modes:

A. Normal Operation (GDS2 for viewing only).

B. GDS2 Commanding TCC in Disabled Operation. (TCC Open).

C. GDS2 Commanding TCC in Enabled Operation. (TCC Locked).

TEST:

Drive the vehicle in 8th gear, V8 mode, with a transmission input speed of 1,050–1,300 rpm with (approximately 64-89 km/h (40–55 mph)) constant throttle input, and engine torque 200-375 Y.

To confirm TCC shudder, the vibration concern must be created in normal operation (Mode A) of the test. If the concern is gone with the torque converter clutch disabled (Mode B, TCC Open) and is gone when the torque converter clutch enabled (Mode C, TCC Locked), the vibration root cause is TCC shudder and the fluid flush procedure corrective action described below should be performed.

If the concern is not present in Mode A, then the vibration concern is not TCC shudder. If the concern is still present with the torque converter clutch disabled (Mode B) or with the torque converter clutch enabled (Mode C, TCC slip speed at zero), the root cause of vibration is NOT shudder. Vibrations not identified as shudder should be further investigated using the “Vehicle Vibration Diagnosis and TAC Requests for Assistance with Vibration Related Complaints” Bulletin.


Service Procedure
Important: Requires NEW DEXRON HP Fluid (GM Part No. 19331925, in Canada 19331926).

Step 1: Cooler Flush, Drain, Clean pan/magnet, Replace Filter (If needed), Oil Fill, & Circulate New Fluid

1 a.) Flush the cooler lines and cooler using published SI Procedures.

1 b.) Remove the transmission fluid pan and drain transmission fluid following SI procedures for the application you’re working on. Discard all oil.

Note: If you find that the fluid is cloudy, milky, or appears to be contaminated with water or engine coolant, DO NOT proceed with below steps. Follow Both SI Procedures for “Cooling System Leak Testing (L83, L86)” and “Engine Coolant/Water in Transmission.”

1 c.) Clean the pan/magnet if any metallic particles present and replace transmission filter if debris is found.

1 d.) Install the transmission fluid pan and refill with new transmission fluid using enough volume to have oil come out of oil level check plug.

Important: Operate the vehicle on the hoist for 10 minutes. Cycle through all forward gear ranges, Reverse and Neutral.

 

Step 2: Drain, Oil Fill, & Circulate New Fluid

2 a.) Remove the transmission fluid pan and drain transmission fluid again. Discard all oil.

2 b.) Install the transmission fluid pan and refill with new transmission fluid using enough volume to have oil come out of oil level check plug.

Important: Operate the vehicle on the hoist for 10 minutes. Cycle through all forward gear ranges, Reverse and Neutral.

 

Step 3: Drain, Oil level Set, and Drive to Evaluate

3 a.) Remove the transmission fluid pan and drain transmission fluid again. Discard all oil.

3 b.) Install the transmission fluid pan and refill with new transmission fluid following the “Fluid Fill Procedure” in SI to obtain correct fluid level.

The shudder should be improved after the completion of this triple flush procedure.

Note: Shudder should improve directionally right away, but for full affect the vehicle may need to be driven up to 322 km (200 miles) and at least two cold to hot drive cycles before determining if the fluid flush corrected the condition or not. Do not re-evaluate vehicle for additional customer shudder concerns until the vehicle has been driven 322 km (200 miles).

[GHuggins]

This seems like a bunch of bull to me... Problem has been the light weight converter engaging and beginning the clutch shear process in lower gears since the 6 speeds... They even redesigned the converter bolts to make them shorter so they couldn't get anywhere near touching the converter itself as any little touch would warp the thin housing during temperature and fluid pressure swelling... GM techs themselves have talked with GM numerous times to try and get them to stop engaging them in the lower gears and make things better as far as the housings goes - GM just won't listen and so they develop a worse and worse reputation...

I still agree that we need slip settings, but once again - I'm not 100% sure this would fix all of the problem...

[SS_bnoon_SS]

PIP5337G fixed my shudder. New converter, fluid, flush, and reprogram. Still seems to search a bit too much for shifts and lockup for my liking. I'd rather it just told a gear instead of downshifting sometimes, but at least the shudder is gone and I can start fresh.

[GHuggins]

Hopefully they improved the design of the converter with the new ones - beefed up the clutch or something? It's most likely shifting and acting like it does now to try and keep from overloading the converter clutch - like we've said - they aren't that great and go back to the very route cause of the problem

[SS_bnoon_SS]

I've had time for the computer to relearn and it is better than before, but the power cut on shifts is still terrible. Lock up is fine for now.

[stan]

Any updates from HP tuners to get access to torque convertor pids? My 8 speed in my 2015 at the start of this thread was fixed by the dealer at about 30k and now I have about 80k on the truck and it is starting to shutter once again. I'd like to lock it up solid in 8th gear.