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6L80 Random trans slip

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Old Oct 10, 2020 | 12:09 AM
  #1  
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Default 6L80 Random trans slip

Hey there bit of a issue with a 6l80 that at random moments feels like it is dropping into neutral while driving along, it will do it four or five times in a 10-15 second period and come good and may not occur again for a few weeks. Scanning with HP Tuners just shows trans slip and nothing else.
So far I have
Pulled the pan, all looks clean, changed to large pan and correct filter with new trans fluid.
Pulled apart valve body, 8 check ball style all perfect no wear in check ***** or separator plate.
Tested resistance across all the solenoids on the TECHM and all are in spec

Car is a 2015 VF SSV L77 6.0L Commodore

Trans slip PCS 1 Cmd pressure rising


Any tips or advice would be appreciated
Cheers
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Old Oct 11, 2020 | 11:00 AM
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From: Portlandia
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what gear are you in when that occurs? that'll help point to whether its a hydraulic issue or a controller issue
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Old Oct 11, 2020 | 03:03 PM
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When it occurs and what gear is odd too, the most times it happens is when first selecting drive it will feel like it is bucking and if given any accelerator will buck violently. If i put the trans into sport mode and while still stationary use the paddle shift it reduces bucking in second and stops in third. The only other times it really happens is when cruising at light throttle around 110kph in 6th on the freeway. The pic in my first post was while i was using cruise control on the freeway an hour into a trip, revs go mental for a few seconds then returns to normal and drove another hour or so without issue.
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Old Oct 11, 2020 | 03:32 PM
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have you tried turning the slip learn back on? there are some funny faults i see in the 6 speeds related to the learn/tq management that never seem to clear.

also what year/model is this transmission? the first couple years were kinda hinky
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Old Oct 11, 2020 | 11:46 PM
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From: Nitro Alley
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Ugh... synchronized shifting...

The tune is very important here!
I would be very careful not to mess around on your own... and have the unit programmed by someone familiar with the transmission and HP-Tuners.

Some more of the guys who use HP-Tuners, hopefully will chime in (as Doug did) and offer more help.
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Old Oct 12, 2020 | 06:12 AM
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Trans has had the issue even when completely stock, a good friend has been tuning for over 30 years is the only one who has touched the tune.
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