2021+ Transmission Service
- Thread starter Nighthawk
- Start date
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fondupot
Full Access Member
Yes, but in this order....
Drop pan and drain fluid
Replace Filter
Reinstall pan w/ new gasket
Top off fluid, overfill slightly
Level Check Procedure.
NOTE: If you overfill correctly in the previous step, during the level check procedure, the excess fluid will drain out the standpipe inside the pan. If you level check, and no fluid comes out, you need to add more fluid and re-level check it.
Additional Note: It's extremely important to make sure the vehicle is level when performing the level check procedure. Otherwise, you will not get the correct fluid level.
A few comments on this entire issue of automatic transmission fluid/filter service.
A. The V8 vehicles have an issue with the exhaust cross over pipe that is very close to the pan and will provide a number of challenges to drop the pan and remove it from the vehicle without either dropping the exhaust or possibly disconnecting the rear trans mount and lifting the trans up a bit. BUT if you plan on installing an aftermarket drain pan, changes are you will need to drop the exhaust to get the new pan in?? The 6 cylinder Diesel vehicles do not have the exhaust cross over pipe under the pan so the procedure is much quicker and easier.
B. Many shops quote prices from a Labor Time Guide which will typically end up with a $800-$1200 price. Even if the shop short cuts the job by disconnecting the rear trans mount and lifting the transmission, many still charge the $800-$1200. I have not looked at the Labor Time on the 6 cylinder Diesel, it should be at least 1/2 the price of the V8 engine models, but often the shops just look up and use the higher labor regardless of the vehicle configuration. These are the shops I clearly would not consider using.
C. There are 2 different trans pan configurations. Some have the "Drain plug" which is not a drain plug at all, it is a bottom fill with a standpipe. If you remove the bottom fill plug while the engine is not running, if you are lucky you may get about 1 qt of trans fluid to drain out! Some of the trans pans do not have the bottom fill feature at all. Unclear which models have the bottom fill pan and which don't. It seems like many of the 3/4 ton/2500 series trucks have the bottom fill plug, earlier builds may have also included the bottom fill type pan. My 2024 does not have the bottom fill feature.
Pan with bottom fill plug
Pan without bottom fill plug
D. The transmission fill procedure is so poorly documented it causes people to possibly damage the torque converter heating the fluid to over 170F and causes a serious burn haz
zard for anyone trying to check and top off fluid at 170F+ temperatures.
The fill procedure should be performed with the fluid at around 100F. If the valve body has not been removed or on the Diesel the external thermostat has not been removed, then the transmission fluid in the cooler and cooler lines will not drain out because the thermostat blocks the fluid from draining.
Fill the transmission cold, WHILE THE ENGINE IS RUNNING WITH TRANSMISSION IN PARK, to where fluid just starts to drain out, then allow the transmission fluid temperature to reach 100F, and WHILE THE ENGINE IS RUNNING WITH THE TRANSMISSION IN PARK, remove the side fill plug or the bottom trans pan fill plug and allow any excess fluid to drain out, then reinstall the plug. My suggestion is drive the vehicle for a few days and reconfirm the fluid level again.
GM came up with a dangerous and stupid fill procedure for these transmission. Nobody had any reason to be trying to check any fluid level at a temperature above 100F as anything higher is clearly a burn hazard and anything over 120-125F is a severe burn hazard.
A. The V8 vehicles have an issue with the exhaust cross over pipe that is very close to the pan and will provide a number of challenges to drop the pan and remove it from the vehicle without either dropping the exhaust or possibly disconnecting the rear trans mount and lifting the trans up a bit. BUT if you plan on installing an aftermarket drain pan, changes are you will need to drop the exhaust to get the new pan in?? The 6 cylinder Diesel vehicles do not have the exhaust cross over pipe under the pan so the procedure is much quicker and easier.
B. Many shops quote prices from a Labor Time Guide which will typically end up with a $800-$1200 price. Even if the shop short cuts the job by disconnecting the rear trans mount and lifting the transmission, many still charge the $800-$1200. I have not looked at the Labor Time on the 6 cylinder Diesel, it should be at least 1/2 the price of the V8 engine models, but often the shops just look up and use the higher labor regardless of the vehicle configuration. These are the shops I clearly would not consider using.
C. There are 2 different trans pan configurations. Some have the "Drain plug" which is not a drain plug at all, it is a bottom fill with a standpipe. If you remove the bottom fill plug while the engine is not running, if you are lucky you may get about 1 qt of trans fluid to drain out! Some of the trans pans do not have the bottom fill feature at all. Unclear which models have the bottom fill pan and which don't. It seems like many of the 3/4 ton/2500 series trucks have the bottom fill plug, earlier builds may have also included the bottom fill type pan. My 2024 does not have the bottom fill feature.
Pan with bottom fill plug
Pan without bottom fill plug
D. The transmission fill procedure is so poorly documented it causes people to possibly damage the torque converter heating the fluid to over 170F and causes a serious burn haz
zard for anyone trying to check and top off fluid at 170F+ temperatures.
The fill procedure should be performed with the fluid at around 100F. If the valve body has not been removed or on the Diesel the external thermostat has not been removed, then the transmission fluid in the cooler and cooler lines will not drain out because the thermostat blocks the fluid from draining.
Fill the transmission cold, WHILE THE ENGINE IS RUNNING WITH TRANSMISSION IN PARK, to where fluid just starts to drain out, then allow the transmission fluid temperature to reach 100F, and WHILE THE ENGINE IS RUNNING WITH THE TRANSMISSION IN PARK, remove the side fill plug or the bottom trans pan fill plug and allow any excess fluid to drain out, then reinstall the plug. My suggestion is drive the vehicle for a few days and reconfirm the fluid level again.
GM came up with a dangerous and stupid fill procedure for these transmission. Nobody had any reason to be trying to check any fluid level at a temperature above 100F as anything higher is clearly a burn hazard and anything over 120-125F is a severe burn hazard.
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You cannot convince me that the transmission fluid maintenance procedure could not be designed to be done the old fashioned way, with a regular dipstick.
fondupot
Full Access Member
Here is the official level check & drain & fill procedures from my tech manual.
With "Lifetime" fluid fill, I guess you do not need a dipstick??
While you have posted the "Official" level check & drain and fill procedure, it is SO BAD what GM has put together. First there is no way the transmission temp will ever get to 167-176F at idle. I have never seen my trans temp over 165F during a 6 hour drive in 100+F ambient temps on the highway, typical trans temp was usually 155F or lower.
Again, 167-176F is stupid dangerous especially around the hot exhaust on the V8 if someone has brake torqued to get the fluid up to these temps. I have seen the exhaust start to glow red hot during brake torque situations. If fluid was to splash on the hot exhaust if could easily flash ignite and not to mention what fluid this temp would do if it splashed on your skin.
I will say this again, IF the valve body has not been removed on a gasoline version trans or the thermostat or cooling lines on the Diesel have not been messed with, the fluid in the cooler lines will not leak out. The ONLY reason the the 167-176F temps are mentioned and they are likely higher for the Diesel, it to make sure the transmission cooling circuit has opened and burped any air out of this loop. Easy enough to perform the 100F fluid fill and level check and then drive the vehicle and check again after fully warming up the transmission. Sure the fluid will expand a bit more at 167F+, but it is not going to be a huge amount to cause any issues.
GM should know better and come up with a safer procedure than what they have posted.
Yet another reason why the GMT800 series is the best of the best.
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