Transmission fluid - 6L80 17 Tahoe PPV

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jabre

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My '17 PPV is at ~120k miles. It had transmission fluid/filter change at 60k. I was thinking about doing it again soon. But, I am now experiencing a slight shudder infrequently in lower gears. Never at cruising. Also, when starting out from a stop sometimes just a very slight lag/jolt.

Last fluid check was 10k miles ago - it was at level and perfect color.
Checked the fluid and found it very black. I pulled some with a vacuum pump from the dipstick. It does not smell burnt. No shiny particulates.
I am very careful about observing my temps. I keep the dash display on trans temp. I know this transmission did not overheat since last checking the fluid.
I checked and there are no error codes.

Local shop wants me to leave the vehicle with them for 3 days just to diagnose.

Suggestions for self diagnosis before taking it to a shop?
- I figure I would plot TCC as I drive to see if I can observe the shudder as slipping.
- Should I bother doing a fluid filter change without a full flush when it is obviously compromised fluid?
- Should I even bother doing a flush without taking it to a shop?

Thanks in advance for your inputs.
 

NickTransmissions

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- I figure I would plot TCC as I drive to see if I can observe the shudder as slipping.
- Should I bother doing a fluid filter change without a full flush when it is obviously compromised fluid?
- Should I even bother doing a flush without taking it to a shop?

Thanks in advance for your inputs.
- Yes - watch TCC slip speed at high duty cycles

- TBD - drop the pan, look at bottom. If black clutch material is observed, put the oan back on with a few bolts and yank it for overhaul

- TBD - depends on outcome of pan inspection
 
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