3 questions for DIY 8L90 fluid and filter change

[Interleukin6]

Hi, almost due for my 1st transmission fluid and filter change for 2022 1500 LTD LT 2.7 with 8L90 (MQE). I have watched a lot of youtube and read other's inputs.... I would like to confirm my questions with you guys to make sure everything is on the right track. 

 

1. As per the owner's manual, Dextron-HP is the fluid I should put in. However, many use Mobil 1 LV ATF HP (blue label) or Amsoil instead. I prefer Mobil 1 anyway. If I use Mobil 1 or Amsoil, will it be compatible with the rest of the original fluid (I guess it is Dextron-HP of course) still remaining in the torque converter and other spaces of the transmission? Again, it is not flush but just change fluid and filter.... I just want to make sure...

 

2. I will do a fluid level check procedure at the end anyway but it is 7.4-7.5 quarts, right?

 

3. Is 35-45C (95-113F) the right transmission fluid operating temperature to check a fluid level for my 8L90? I have also read "if vehicle is equipped with a thermal bypass valve, the transmission level should be checked only after the TFT has reached or exceeded an operating temperature of 90C (194F). Once the TFT has reached or exceeded 90C (194F), then turn OFF the vehicle and allow the TFT to cool back down to 35-45C (95-113F) before checking the fluid level as required. Reaching or exceeding an operating temperature of 90C (194F) opens the bypass valve and allows the cooler to fill up with fluid, which will result in a more accurate fluid level check" How do I know mine has the thermal bypass valve or not? Just go for 194F then cool it down to 95-113F? I have noticed it is quite hard to reach 194F. I found it is only 183F when driving mine at 70 mph on the highway for 1 hour.

 

Please share any pro tips on top of answers to my questions. Appreciate your input in advance. 

 

 

[newdude]

17 hours ago, Interleukin6 said:

Hi, almost due for my 1st transmission fluid and filter change for 2022 1500 LTD LT 2.7 with 8L90 (MQE). I have watched a lot of youtube and read other's inputs.... I would like to confirm my questions with you guys to make sure everything is on the right track. 

 

1. As per the owner's manual, Dextron-HP is the fluid I should put in. However, many use Mobil 1 LV ATF HP (blue label) or Amsoil instead. I prefer Mobil 1 anyway. If I use Mobil 1 or Amsoil, will it be compatible with the rest of the original fluid (I guess it is Dextron-HP of course) still remaining in the torque converter and other spaces of the transmission? Again, it is not flush but just change fluid and filter.... I just want to make sure...

 

2. I will do a fluid level check procedure at the end anyway but it is 7.4-7.5 quarts, right?

 

3. Is 35-45C (95-113F) the right transmission fluid operating temperature to check a fluid level for my 8L90? I have also read "if vehicle is equipped with a thermal bypass valve, the transmission level should be checked only after the TFT has reached or exceeded an operating temperature of 90C (194F). Once the TFT has reached or exceeded 90C (194F), then turn OFF the vehicle and allow the TFT to cool back down to 35-45C (95-113F) before checking the fluid level as required. Reaching or exceeding an operating temperature of 90C (194F) opens the bypass valve and allows the cooler to fill up with fluid, which will result in a more accurate fluid level check" How do I know mine has the thermal bypass valve or not? Just go for 194F then cool it down to 95-113F? I have noticed it is quite hard to reach 194F. I found it is only 183F when driving mine at 70 mph on the highway for 1 hour.

 

Please share any pro tips on top of answers to my questions. Appreciate your input in advance. 

 

 

 

 

1 - Mobil LV ATF HP = Dexron HP.  The Mobil IS the factory fill and factory fluid.  DO NOT MIX FLUIDS or you will have a bad time.  If you are trying to switch to Amsoil, you need enough to drain and fill the transmission about 3-4 times to get as much of the factory fluid out of there.  Probably 16-20 quarts.  

 

2 - Approximate pan drop is 7.4 quarts.  

 

3 - I don't think the L3B 8 speed has a thermostat.  V8s with the 8L90 have one in the cooler lines.  L3B with the 8 speed have an oil (transmission) to water (coolant) heat exchanger for the cooler.  Unless its inside there or internal to the valve body, I don't think it has one.  Would it hurt to get it to 194F or higher?  Not at all but it might not be necessary.  95-113F is the correct set range however.  I can get mine to 190+ no issues.  Do some stop and go city driving, maybe a couple hard accelerations, brake torque it a bit too (not too long just 5-7 seconds).  

Edited February 24 by newdude

[Interleukin6]

7.4 quarts of Mobil 1 LV ATF HP and check its level when TFT at 95-113F! Aye aye, captain! Thank you so much. 

[Gangly]

You do need to set the fluid level at the correct temperature range.  Mine will SLOWLY drip out of the fill hole when the transmission is at the requested temperature range, but it will pour out of the fill hole if it is significantly hotter.  Basically, if you measure your fluid level when the transmission fluid temperature is too high, more fluid will pour out than it should, leaving you with less fluid in your transmission than specified.

[Black02Silverado]

When the dealership does a fluid exchange on the 8L90 they use 20qts.  This is what they told me.  Makes sense since they want to make sure they get all the old fluid out and new in.  As for AMSOIL, you will need the ATL product code.  It is the ATF with the blue label.  You can get it here or contact me if you want to get it at a discount.

 

[Interleukin6]

Thank you Gangly and Black02Silverado (I will do a pan drop only, not fluid exchange.... I think it is a little bit too much for me). I was underneath my truck today to take a look.... Oh man, it seems that removing 3 bolts of the heat shield will be the hardest job during this work. There is NO space for the top 2 bolts. To make matters worse, I also saw a nut below each bolt. The nuts will not drop after removing the bolts? If yes, I have no idea how I can align the nuts when putting the bolts back there later because again literally there is no space to put my hand in. Another question is.... a truck must be leveled for the fluid level check. Mine is a stock LT in which the front is ~2 inches lower than the rear as we all know. Should I put 1 or 2 2-inch (actually 1.5-inch each) lumbar under the front tires to make it "leveled" or just putting the truck on the flat garage floor is more than enough? If I use 4-point jack stands, should I put the same height of jack stands under the frames to make it "leveled"? Please correct me if I am wrong. I think, for example, if I put them under the rear axles, my truck cannot be leveled due to rear suspension travel. Sorry for the dumb questions. Thank you again. 

Edited February 27 by Interleukin6

[Black02Silverado]

19 hours ago, Interleukin6 said:

Thank you Gangly and Black02Silverado (I will do a pan drop only, not fluid exchange.... I think it is a little bit too much for me). I was underneath my truck today to take a look.... Oh man, it seems that removing 3 bolts of the heat shield will be the hardest job during this work. There is NO space for the top 2 bolts. To make matters worse, I also saw a nut below each bolt. The nuts will not drop after removing the bolts? If yes, I have no idea how I can align the nuts when putting the bolts back there later because again literally there is no space to put my hand in. Another question is.... a truck must be leveled for the fluid level check. Mine is a stock LT in which the front is ~2 inches lower than the rear as we all know. Should I put 1 or 2 2-inch (actually 1.5-inch each) lumbar under the front tires to make it "leveled" or just putting the truck on the flat garage floor is more than enough? If I use 4-point jack stands, should I put the same height of jack stands under the frames to make it "leveled"? Please correct me if I am wrong. I think, for example, if I put them under the rear axles, my truck cannot be leveled due to rear suspension travel. Sorry for the dumb questions. Thank you again. 

You will be fine as long as it is on a level surface.  No worries.  As for the bolts, sorry can't help there but maybe YouTube can help.

[fondupot]

Here is some procedures I pulled for you from my service manual, these should help. I haven't done this myself on my 2022 Silverado LTD 8 speed. But I did it on my 2019 GMC Canyon 8 speed.

 

The best tip I have for you is to slightly overfill the pan on the initial fill. It will drain down to the correct level during the temperature level procedure.

 

ALLDATA diy.pdfTorque Specs.pdfTransmission Fluid Level and Condition Check (Fluid - A_T) - ALLDATA diy.pdfAutomatic Transmission Fluid, Fluid Pan and_or Filter Replacement (L3B) (Fluid Filter - A_T) - ALLDATA diy.pdfTransmission Fluid Fill Procedure (Fluid - A_T) - ALLDATA diy.pdfTorque specs 2.pdf

 

For reference here is my 8L45 video for my Canyon. Should have similar process for the 8L90 MQE.

Be

[Interleukin6]

Fondupot, I really appreciate your input. Thank you so much.