Transmission fluid - 6L80 17 Tahoe PPV

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.

jabre said:

- 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.

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- 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

@NickTransmissions, thanks for the quick feedback.

Yes, TCC slip at high duty cucles.
Yes, clutch material in pan.

Question - how do I know whether this is TC failure only vs internal transmission?

jabre said:

Yes, TCC slip at high duty cucles.
Yes, clutch material in pan.

Question - how do I know whether this is TC failure only vs internal transmission?

Click to expand...

Good question - how much do you want to do on your own?

Given you have clutch material in the pan, there's no question it's coming out for overhaul...But to answer your question of what came first, the chicken or the egg (i.e. did the converter fail first or did the transmission play a role in its failure), you'll need to do some vacuum testing as well as a physical inspection of the unit once you have it apart.

Let me know if you think you may want to tackle the job yourself and we can go from there.

Good question - how much do you want to do on your own?

Click to expand...

Last transmission fail (older tahoe with 4l60) I purchased an upgraded reman and had it installed. It performed better than the original. But, when all was done I told myself I would do the swap myself next time. Unfortunately, the previous reman provider is out of inventory of this trans right now. I don't know if I want to take on the full rebuild. I am free time constrained.

Just got an estimate from local, well web-reviewed shop. $6400 to $6800. Indicated that 60% of his business right now is 6l80's. He won't provide a part replacement list until they are done. But, he said they upgrade over OEM. Not trusting already when he won't give me details. I asked about GM and he indicated add $750 for an un-upgraded replacement reman from GM.

If there is a thread I overlooked that has a recommended upgrade parts list I would appreciate a link. I searched and found the post on the 6l80 that indicated HD recommendations but not standard. I could try to walk through the list with this shop and see what he says.

I'm in the Austin area. If anyone has recent, good experience with a reasonably priced, quality upgrade rebuilder please let me know. I'm in the market for a second 'fun' car. I might just pull the trigger on that and garage the Tahoe and pull the trans later - either when I can get the reman or when I am ready to take on the rebuild.

jabre said:

If there is a thread I overlooked that has a recommended upgrade parts list

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see my signature line - I put all the links to threads I start in that line.

@NickTransmissions, thank you. I had overlooked page 1 detail in your thread. Got the list plus the recommended torque converter with .050” or thicker converter clutch w/ billet cover from later in the thread.

Again, anyone else have recommendations from experience in Austin area on rebuilders, or responsive and quality remanufacturing company please speak (message) up.

jabre said:

@NickTransmissions, thank you. I had overlooked page 1 detail in your thread. Got the list plus the recommended torque converter with .050” or thicker converter clutch w/ billet cover from later in the thread.

Again, anyone else have recommendations from experience in Austin area on rebuilders, or responsive and quality remanufacturing company please speak (message) up.

Click to expand...

You're welcome, man...Good luck with your search for a trans shop...There's gotta be at least one good transmission rebuilder in the Austin area. If you do strike out though, you can always purchase a GM Reman - 3yr/100k warranty and it's plug and play; no programming or fast adapt relearn needed...They just need last 8 digits of your VIN to ensure you have the right operating software version loaded onto the TEHCM.

I have spent hours researching, calling and asking questions of multiple local shops and remanufacturers. Finally I found another post recommending Phoenix Transmissions in Weatherford, TX. I called and immediately was comfortable with this outfit working on my vehicle. I let him tell me what needed to be done. After his explanation I think even @NickTransmissions would approve I'll be dropping off my vehicle with him next week. It is a three week turn as he is so busy. But, for years of peace of mind well worth it. I will update this thread with my impression of the results after it is done.