2017 Chevy Tahoe Premier 4x4 Trans service, rebuild, Dex VI fluid, MagRide

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jj88

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I wanted to post this as as helpful info/comments and questions for the internet-verse.

2017 Tahoe Premier 4x4 purchased at 32.2k miles in 2021 with 5.3L EcoTec3 V8 AFM and MagRide

MagRide front shocks went bad about 40k miles. ~$400 each, part cost. FYI. Kinda early? Tahoe did have a 3" body lift put on around 35k miles which may have messed with the MagRide computer to damage them early? Don't know.

Mag-Hytec GM 12-9.5 Alum Diff Cover Installed, with after market sway bar Spohn.

Transmission service at 34.7k miles, adding B&M alum trans pan. Old Pan donut magnet had quite a mound of detritus on it for 34.7k miles, I had thought at the time. Used Valvoline Dex VI approved fully synthetic fluid back in, ~8 qts. Trans total fill is 12.2 qts, now with new pan probably an extra quart. Runs fine at this point. ~39% old fluid, ~61% new Valvoline.

2nd Trans service at 38.8k miles, to check on the fluid after long tows. another 7.5 qts D/F of Valvoline Dex VI. So now roughly the fluid is 22% old fluid, and 78% new Valvoline Dex VI ATF Fully synthetic.

Now the trouble starts. Soon after the 2nd trans service:

The final Overdrive gear will not engage anymore once the trans fluid is a operating temp (over 120 F to normal 175 F). It still will engage if the fluid is cool during first 20-30 minutes of driving.

After enough of this, it was taken to the dealer and was rebuilt under warranty, the dealer claiming the after market trans pan was causing this issue.

I personally do not think this is the reason, although I know there is debate on the internet about after market trans pans and after market diff covers.

I personally think it was the fully synthetic (extra slippery) Valvoline Dex VI approved ATF fluid. Only $5 a quart, pretty cheap. After the percentage of the Valvoline got too high after the 2nd D/F, it was too slippery for the transmission, IMO. I had another minor trans slip problem with a '16 Camry where I used RedLine D6 (known to be slippery, I found out) instead of the non-synthetic Toyota WS ATF (or Valvoline Maxlife is said to work fine as well).

Anyway, I think the dealer, instead of concluding an aftermarket Dex VI approved fluid could be the culprit, claimed the Trans Pan as the problem, but rebuilt it under warranty anyway. Because a Dex VI approved fluid causing problems in a Dex VI trans would cause major legal trouble for them.

Anyway, I service stuff to take care of things, make them last and save money and prevent problems. And yes save the environment so that less junk ends up in the junk yard. Base oils can be recycled.

In doing so, using a Dex VI approved fluid I "caused" problems, wasted time and money, and this bugs me.

On the service record they filled the rebuilt transmission with ACDelco OEM GM "non fully synthetic" Dex VI ATF (part # 88865602, 10-9395)

GM/ACDelco also have a Fully Synthetic ACDelco OEM GM Dex VI fluid (part # 88865618, 10-9244), which they did not use for some reason, even though its a 2017.

That being said, when I later serviced a 2014 Chevy Camaro, what ATF did I use? Valvoline? No, ACDelco GM OEM non-fully synthetic Dex VI ATF (88865602, 10-9395).

Do y'all think it was the fluid or the pan? Or was the trans just worn out from previous owners?

Take care
 

Blackcar

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In 2015 to 2017 transmissions take a new mobile 1 blue label fluid there is a TSB on using this fluid and the GM dealer that rebuilt your trans should know that. Had my 2017 changed for free on this TSB.
 
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jj88

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Hey Blackcar, thanks for chiming in.

As I was trying to research the TSB you were talking about, I did find a forum thread that was talking about the Mobil 1 LV ATF HP blue label fluid.


However, this 2017 Tahoe has the 6-speed transmission, which takes Dex VI. Its the 8-speed I believe that has the updated Mobil 1 LV ATF HP fluid which helps solves problems with it.

Anyway, I could be wrong that the fully synthetic Valvoline Dex VI ATF I used is more slippery than the synthetic blend ACDelco OEM GM Dex VI fluid which was used at the Dealer. But I am still curious if anyone has any insight on this.

take care
 

Blackcar

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Hey Blackcar, thanks for chiming in.

As I was trying to research the TSB you were talking about, I did find a forum thread that was talking about the Mobil 1 LV ATF HP blue label fluid.


However, this 2017 Tahoe has the 6-speed transmission, which takes Dex VI. Its the 8-speed I believe that has the updated Mobil 1 LV ATF HP fluid which helps solves problems with it.

Anyway, I could be wrong that the fully synthetic Valvoline Dex VI ATF I used is more slippery than the synthetic blend ACDelco OEM GM Dex VI fluid which was used at the Dealer. But I am still curious if anyone has any insight on this.

take care
Ok Thanks for information.
 

gat0r

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def. not the pan... dealers can be sticklers...as well as being dumb ;) lol

the 8 speeds are known to have issues. (so many there are multiple class action lawsuits)
converter being 1 of the largest issues (shudder)

your issue was prolly caused by programming issue in TCM, which is also known to GM
 
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jj88

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def. not the pan... dealers can be sticklers...as well as being dumb ;) lol

the 8 speeds are known to have issues. (so many there are multiple class action lawsuits)
converter being 1 of the largest issues (shudder)

your issue was prolly caused by programming issue in TCM, which is also known to GM
Dang.

So do y'all think is it likely to keep happening, and need another trans rebuild sooner that usual?

It's at ~45k miles now. Warranty rebuild was at 39k miles.
 

91RS

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Neither. The transmission was already failing.
 

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