Sanity Check on 8L90 Filter Change

[nominion]

I'm approaching 30,000 miles on my 2018 Sierra with the 8 speed transmission.  At this point, with all of my previous vehicles (2013 Yukon w/6L80 for example), I drop the transmission pan, change the filter, and refill with the same amount of fluid that I removed.  My Sierra doesn't necessarily exhibit the "shudder" problem that others experience, but I do get a rough shift from first to second in the morning on some occasions.  With that, I plan to do the process I mentioned previously to my 2018 Sierra, using the following items:

 

- A hand operated fluid pump to remove the old fluid via the fill hole on the transmission.

- 12 quarts of Mobil 1 Synthetic LV ATF HP (blue label).

- 1 ACDelco TF922 Professional Automatic Transmission Fluid Filter.

- A hand operated fluid pump to add the new fluid via the fill hole on the transmission equal to the amount that was removed.

 

Once complete, I will check the fluid level using the below procedure (found here).

 

I've watched the video on YouTube about checking the fluid level which lines up with the below procedure, but I haven't found a good document that describes the filter and fluid change process, other than having the dealer triple flush it as outlined in the TSB (no filter change), which I'm not convinced is necessary in this case.  

 

I assume the process I outline above, based on what I've done for the 6L80, is applicable to the 8L90, with some variation in refilling?

 

For those of you who have done this before or have more experience than I do with the 8L90, can you please chime in and confirm/deny I'm on the correct path?

 

Thank you!  

 

This procedure checks both the transmission fluid level, as well as the condition of the fluid itself. Since the transmission on this vehicle is not equipped with a fill tube and dipstick, a tube in the bottom pan is used to set the fluid level.

Caution: The transmission fluid level must be checked when the transmission fluid temperature (TFT) is between 35–45°C (95–113°F). If the TFT is not within this range, operate the vehicle or allow the fluid to cool as required. Setting the fluid level with a TFT outside this range will result in either an under or over-filled transmission. TFT>45°C=under-filled, TFT<35°C=over-filled. An under-filled transmission will cause premature component wear or damage. An over-filled transmission will cause fluid to discharge out the vent tube, fluid foaming, or pump cavitation.

Note: CTS-V/LT1 Camaro, if running a track session, should have the transmission fluid level checked when the transmission fluid temperature (TFT) is between 55-65°C (131–149°F).

 

Caution: THE ENGINE MUST BE RUNNING when the trans oil level check plug is removed or excessive fluid loss will occur, resulting in an under-filled condition. An under-filled transmission will cause premature component wear or damage.

Note: Continue to monitor the TFT. If the TFT is not within the specified values, reinstall the trans oil level check plug and repeat the previous steps.

Caution: Refer to Fastener Caution.

1. Observe the TFT using the driver information center (DIC) or a scan tool.
2. Start and idle the engine.
3. Depress the brake pedal and move the shift lever through each gear range. Pause for at least 3 seconds in each range. Move the shift lever back to PARK. Ensure the engine RPM is low (500–800 RPM).
4. Allow the engine to idle for at least 1 minute.
5. Raise the vehicle on a hoist. The vehicle must be level, with the engine running and the shift lever in the PARK range.
6. Remove the transmission oil level check plug (1) from the transmission fluid pan. Allow any fluid to drain.
   • If the fluid is flowing as a steady stream, wait until the fluid begins to drip.
   • If no fluid comes out, add fluid until fluid drips out. Refer to Transmission Fluid Fill Procedure.
7. Inspect the fluid color. The fluid should be red or dark brown.
   • If the fluid color is very dark or black and has a burnt odor, inspect the fluid and inside of the bottom pan for excessive metal particles or other debris. A small amount of “friction” material in the bottom pan is a “normal” condition. If large pieces and/or metal particles are noted in the fluid or bottom pan, flush the oil cooler and cooler lines and overhaul the transmission. If there are no signs of transmission internal damage noted, replace the fluid filter assembly, repair the oil cooler, and flush the cooler lines.
   • Fluid that is cloudy or milky or appears to be contaminated with water indicates engine coolant or water contamination. Refer to Engine Coolant/Water in Transmission.
8. Replace the transmission oil level check plug and tighten to 9 Y (80 lb in).
9. Inspect for external leaks. Refer to Fluid Leak Diagnosis.

[CDNSS]

That’s the procedure I’m gonna follow next week on my 8L90 in my Sierra 6.2 AT. I’m at 30k too goin to drop pan and change filter I just can’t see having the dealer flush trans without changing filter and cleaning pan 

My truck goes  in for the warranty trans fluid upgrade / flush so um doin the filter / pan drop myself first  maybe overkill but just makes sense to me 

 

 

 

[16LT4]

I haven't done a filter job on the 8L, but have on plenty of BMWs (using the 6L45) whose procedure is the same (no dipstick/fill tube).  It's definitely not hard or daunting.  One thing I would suggest paying very close attention to is transmisson fluid temperature: if you fill with the transmission at operating temperature, you'll wind up underfilling the transmission (operating temp is 180-190* F, but filling temp is ~100*.  On the BMWs, I used my scanner to read both fluid and substrate temps, but you could also use a laser temperature gun on the pan to get a good idea.  Rule of thumb is if you can't keep your hand against the pan, the temperature is too hot.  

[nominion]

Thanks for the feedback.  Glad to know I'm going about this the correct way.

 

My plan was to do the filter change and fluid replacement at ambient temperature, not with the transmission at operating temp.  Once I've replaced the same amount of fluid I took out, I would follow the procedure to bring the transmission up to temp and then check the fluid level, adding/removing fluid as necessary.  

Since there is no drain plug, I have no desire to drop the pan with transmission fluid at operating temperature.  That's just asking for misery.  

[16LT4]

23 minutes ago, nominion said:

Thanks for the feedback.  Glad to know I'm going about this the correct way.

 

My plan was to do the filter change and fluid replacement at ambient temperature, not with the transmission at operating temp.  Once I've replaced the same amount of fluid I took out, I would follow the procedure to bring the transmission up to temp and then check the fluid level, adding/removing fluid as necessary.  

Since there is no drain plug, I have no desire to drop the pan with transmission fluid at operating temperature.  That's just asking for misery.  

Good deal; with the pan off, you may want to add a drain plug (or buy a new pan and install a plug in that one so you retain your factory pan) in order to facilitate future drains; this definitely won't be the last one you'll do.  Draining the pan only gets out about half anyway; I typically do several drain/fills before saying "good enough."  A bottle of Lubeguard Red would definitely help prevent any future issues on your final fill.  I've emptied plenty of pans in the past, and there is a knack for not wearing it, but a drain plug definitely makes it much easier.  I've also never measured what's come out simply because I don't trust previous fills by others, but will give you a good guestimate so you know what to dump back in before having to start measuring fill level.

[tyler.frost92]

Adding a drain plug is a good idea. I ordered a stock pan for about 35 dollars new on ebay, and had a plug welded in, that way i could swap it right in after pulling my old pan off and changing the filter. Contrary to what GM says, you can remove the pan with the exhaust in place, I used the bottle jack that came with the truck, and placed it in between the body and exhaust and cranked it by hand to bend the exhaust out of the way maybe 1/4 inch. To make things even easier I also ordered a dipstick tube and dipstick from a guy on ebay who makes them for 8 speed camaros. It fit my truck with a little bit of modification. Then I used the procedure you listed above to get the fluid level right. I only ended up using about 8 quarts.

[tyler.frost92]

 

 

This video will show you exactly what you need to do. 

 

[nominion]

Thanks for the video!  Very cool. 

 

I honestly don't mind having to drop the Y pipe to remove the pan. It gives me a chance to put anti-sieze on the manifold bolts which helps when it comes time for future exhaust work.