`16 Suburban 6L80 Thermostat Update

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On my `16 Chevy Suburban with the 6 speed and 5.3 L, I just did the change to the lower temp. thermostat as per TSB 21-NA-199 which lowers the temp 26 degrees F or 20 C. New full open temp. is 158F or 70C.


I wasn't having any issues, just wanted to perform this update to hopefully prolong tranny life.

Only lost about 2 oz, during the thermostat swap. However, did notice some metal particles in the fluid. I will be sure to perform a pan drop and a filter change around 30,000 miles. I know the pan is a pain to get off due to the exhaust being in the way. Saw the tricks to get it off on YouTube.

Any preference as to what Dexron 6 to use? Should I just stick to a name brand Dex 6, like Valvoline, Mobil, AC Delco, etc. or would I be better off with Amsoil Sig Series ATF or Redline D6? Looks like it will be around 6 quarts, the price doesn't bother me for Amsoil or Redline and I already have an Amsoil account. But would I better be served with a Dex 6 specific fluid.

I believe most of the failures are due to the Torque convertor being shot around 150,000 miles and shed metal throughout. The engineering design, slips the convertor during AFM to reduce the vibration of the engine running on 4 cylinders. Something tells me it is a design issue, not a maintenance issue that causes the failures, however good maintenance should help.
 
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I worked on forklifts and industrial equipment and did some work of semis and the company vehicles. I am far from a trans expert but I will say the oil and filter being changed regularly will let the trans live but there isn't an oil that will compensate for poor quality or poorly engineered parts.
 
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On my `16 Chevy Suburban with the 6 speed and 5.3 L, I just did the change to the lower temp. thermostat as per TSB 21-NA-199 which lowers the temp 26 degrees F or 20 C. New full open temp. is 158F or 70C.
Isn't that going to set a low engine temperature code? I just put in a 180F thermostat in my Olds 88 and the gauge stays at the quarter mark on the gauge.
IMG_20220907_114717614.jpg

Love seeing the extra cushion but can imagine 158F would cause problems with the heater in the winter.
 

zfasts03

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This is the transmission thermostat, on the front/side of the transmission that feeds the trans cooler lines. Engine temperature thermostat is unchanged.
 
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Looks like GM / AC Delco has changed the formulation of their Dexron VI to semi synthetic….

Old stuff was 109243…

I just bought 12 quarts to do my Dad’s Cruze…

 
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Looks like GM / AC Delco has changed the formulation of their Dexron VI to semi synthetic….

Old stuff was 109243…

I just bought 12 quarts to do my Dad’s Cruze…

You can buy ACDelco Dexron VI in both the full-synthetic and semi-synthetic varieties. Both are available on Amazon.

ACDelco GM Original Equipment 10-9244 Dexron VI Full Synthetic Automatic Transmission Fluid - 1 gal

ACDelco GM Original Equipment 10-9395 Dexron VI Automatic Transmission Fluid - 1 gal

Since I live in cold Alaska, I always opt for the full-syn...
 
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I believe most of the failures are due to the Torque convertor being shot around 150,000 miles and shed metal throughout. The engineering design, slips the convertor during AFM to reduce the vibration of the engine running on 4 cylinders. Something tells me it is a design issue, not a maintenance issue that causes the failures, however good maintenance should help.

That is correct, It's cheaper to do a Billet Front Converter, TransGo Tow & Pro kit, And a trans tune/disabling the AFM NOW versus letting it fail.
 

4WD

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I put a Range module in our 2017 Tahoe because it was just too “busy” in/out of 4/8 cylinders
Once I got a drain plug in - gets a pan dump/fill every Spring - 20 minutes
 
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wlk

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Once you do the filter change and barring no future flakes warranting a filter swap, I would either put a drain plug on the pan or just siphon it out the fill tube every year and refill. ....I assume it has a fill hole still.... Yes it is only a few qts but done every year will keep it fresh and probably last for the life you have it. Also would look at the above to help with the 4/8cyl nonsense. Good luck
 
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4WD

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Once you do the filter change and barring no future flakes warranting a filter swap, I would either put a drain plug on the pan or just siphon it out the fill tube every year and refill. ....I assume it has a fill hole still.... Yes it is only a few qts but done every year will keep it fresh and probably last for the life you have it. Also would look at the about to help with the 4/8cyl nonsense. Good luck
They still use fill tubes with hot/cold level marks on dipstick …
 
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I have a 2017 Tahoe with the 6L80 and the TQ shredded metal into the unit and was on the way to it failing (88k) and I went ahead and had it rebuilt. Use a Billet TQ, the updated Thermostat and Sonnax shift kit and valves. The one thing I wish I would have done was have the shop put a pan with drain on it - messed up there.

I am not completely sold on this rebuild because I am getting very stiff/abrupt downshifts between 4 to 3rd and 3rd to 2nd. Not so much on the shift to the upper gears. The shop used BG trans fluid and I am, wondering about changing it to the syntheic ACdelco. I have read some posts on the Chevy sites these 6 & 8 speeds are finicky about fluid?

Anyway, just thought I would share.
 
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Billet Front Converters, Especially those without Damper Springs require a custom calibration (Tune). It's tougher to modulate TCC Slip with billet front/multi disc converters.

For this complaint.....The first thing I do is disable the TCC apply in 1st-4th gears, If the symptom of harsh downshifts persist.....I start looking at the Compensator valve & circuit, I've seen many a hung Compensator Valves from not cleaning the unit well enough or reusing coolers.
 
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