8 Speed 8L90 DIY Flush

[2018GMC]

I'm thinking of doing a DIY at home flush on my 2018 6.2 with 8l90. Only has 20k on it and shifts great but have heard that the OEM fluid is hydroscopic and slowly absorbs water over time which causes shudder and shifting issues.

I'm betting I need 12 quarts to do the flush at home, possibly more if I want to change transfer case atf as well which holds 3 pints.

Looks like I could do this at home DIY flush in the driveway by:
1. Drop pan, remove old fluid and clean pan, replace filter.
2. Install pan and add 4 quarts of fluid.
3. Remove the cooler block, inserting some poly line in the cooler port on side of transmission towards front of vehicle.
4. Fill transmission with 4 quarts of new fluid.
5. Run engine for 45 - 30 seconds to flush torque converter. Repeat until fluid is clean coming out of poly line.
6. Blow cooler lines out with compressed air
7. Replace cooler lines onto side of transmission.
8. Fill with new fluid and check level.
 

8L90 flushing proceedure.pdf 8 Speed Fluid Level Check.pdf 8 Speed Fluid Fill Procedure.pdf 8 Speed Fluid Change.pdf

[2018GMC]

Looks like the Mobil 1 LV Blue label 124715 is $46 for a 6 pack on the jungle website. They have a pic of the old black label but several reviews say it is actually the Blue label 124715
Amazon.com: Mobil 1 Full Synthetic LV Automatic Transmission Fluid HP, 6-Pack of 1 quarts : Automotive

What about using Valvoline Multi-vehicle 773775?
Valvoline MaxLife Multi-Vehicle Full Synthetic Automatic Transmission Fluid (ATF) 1 GA - Walmart.com

[newdude]

2 minutes ago, 2018GMC said:

Looks like the Mobil 1 LV Blue label 124715 is $46 for a 6 pack on the jungle website. They have a pic of the old black label but several reviews say it is actually the Blue label 124715
Amazon.com: Mobil 1 Full Synthetic LV Automatic Transmission Fluid HP, 6-Pack of 1 quarts : Automotive

What about using Valvoline Multi-vehicle 773775?
Valvoline MaxLife Multi-Vehicle Full Synthetic Automatic Transmission Fluid (ATF) 1 GA - Walmart.com

 

 

Get the right stuff.  Do NOT use the multi-vehicle which when clearly looking at the compatibility chart for it covers Dexron 2, 3 and 6 only, NOT HP.  

[2018GMC]

21 hours ago, newdude said:

 

 

Get the right stuff.  Do NOT use the multi-vehicle which when clearly looking at the compatibility chart for it covers Dexron 2, 3 and 6 only, NOT HP.  

Only other compatible fluid I can find is Amsoil Signature Fuel Efficient ATF which is the most expensive at $18.69 per qt, $14.39 per qt if you buy the gallon and you are preferred customer. https://www.amsoil.com/p/signature-series-fuel-efficient-synthetic-automatic-transmission-fluid-atl/?code=ATLPK-EA

Looks like I'll prob be going with Mobil 1 LV Blue label 124715 for &7.36 per quart when you buy the 6 pack

Edited October 11, 2022 by 2018GMC

[rav3]

I believe you can get the dealer to do it free if you complain about the shifting 

https://gmauthority.com/blog/2019/08/tsb-seems-to-fix-8-speed-automatic-gm-transmission-problems/

[JimCost2014]

1 hour ago, rav3 said:

I believe you can get the dealer to do it free if you complain about the shifting 

https://gmauthority.com/blog/2019/08/tsb-seems-to-fix-8-speed-automatic-gm-transmission-problems/

That is what I did.

[2018GMC]

If there was a dealership that had a service department that’s worth a $hit near me, I’d do the TSB but I’ve been to both the GMC and Chevrolet dealer and they both suck. Several hours for a oil change, they don’t call when it’s done. One of the dealers smashed my Evap canister using it as a jack point. Didn’t find out about that until weeks later when I got a check engine Evap small leak. Of course both denied responsibility.

 

So here I am doing it myself

 

The filter will get changed when I do the work and the pan cleaned since the dealer just hooks up the flush machine and then they’re done. 

Edited October 10, 2022 by 2018GMC

[Gagliano7]

Will trans fluid be covered by powertrain warranty?  Mine is starting to feel like i am driving over rumble strips at times which everyone says is the trans fluid.

[NWI Denali]

17 hours ago, Gagliano7 said:

Will trans fluid be covered by powertrain warranty?  Mine is starting to feel like i am driving over rumble strips at times which everyone says is the trans fluid.

Yes, covered under 5/60 powertrain