Considering how GM screwed us with the oil, what about the ATF?

[Vector]

Years ago before synthetic oil, I was running 20W50 in most of my motors (some HP applications) and never thought about fuel efficiency, I just wanted the most protection possible. Never did I have an engine failure.

In recent years GM has told us we MUST use the every thinning oil to maintain our warranty, and most of us presumed it was best for the engines health, as why else would they say the warranty would be invalidated.
Yet today we have come to find out those mandates were not based on our engines best interest, protection, nor longevity. Rather it was to meet stringent CAFE standards, and thinner motor oil with less resistance meant their vehicles got a slight improvement in fuel efficiency, thereby saving them millions of dollars. Thus they had us using practically water with 0w20, and their recall protocol now is to use 0w40.
Keep in mind that in Europe and other countries the exact same engine mandates 5w30 because they do not have the CAFE standards over there.
They likely also calculated that when the engines fail it will typically be after the warranty, and then depending on how much the repairs and future problems would cost, they could sell you a new vehicle.

So, if they did that with motor oil, who is to say they didn't also do it with transmission ATF viscosity for the same reason. The measurement of Kinematic Viscosity is higher with thicker viscosity and the lower it goes, the thinner and less resistance it provides which also increases fuel mileage.
Don't get me wrong, I like better fuel economy as well, but engine/transmission protection and longevity is far more important to me, and failure of either will result in a much greater cost than the couple of extra miles per thankful.

Additionally, it has always made me wonder why the temperatures of our GM transmissions be it the 6 - 8 - and now 10 speeds run consistently hot, despite many of us having towing packages, which means individual coolers for our trannys.
Recently speaking to a transmission guy, he said heat and friction are killers of transmissions, just like it is with engines.
He explained that GM wants the ATF to heat up as quickly as possible to help thin out the viscosity for the same aforementioned CAFE reason. Thus they use the bypass valve which restricts the ATF from going thru the cooler until it reaches around 196 degrees. That means your temp once at the designated point is not going to drop back down below it.
As a bonus, if the bypass gets stuck closed and the ATF cannot get to the trans cooler, you could wind up with too hot a transmission and damage it.

My question to you'll is now that you don't trust GM to do what is best for the consumer regarding motor oil because of CAFE, should we trust them with the ATF mandates using their AC Delco Dexron ATF vs. another brand and/or viscosity?
If you are using something else what brand/viscosity are you using?
Also, how many of you have done the bypass valve block kit, or even an aftermarket free flow valve which keeps the temperatures much lower under all conditions?

 

[NickTransmissions]

The ATF formulation is based on the design/chemical engineering of the friction material used in the lined clutch plates inside a given automatic transmission. So if a particular transmission calls for a specific type of fluid, that is the fluid you must use.

This is little different than engine oil which has viscosity ratings that vary based on intended usage as well as engineering parameters. Most OEMs base their recommended viscosity per bearing clearances. However, as we have all seen, sometimes the recommended viscosity is not optimal and trades off protection a bit too much relative to what gains may be realized by using the rec’ed oil viscosity. I run 10W-40 in my LH6 5.3L even though it calls for 5W-30. I do this because I value bearing protection over other considerations.

However I run Dex6 synthetic in the 6L80 it’s equipped with because that is what the friction material was designed to work with. Using other fluid wont allow it to work optimally (in fact may be severely harmful for the unit, depending on what’s put in).

 

[Vector]

The ATF formulation is based on the design/chemical engineering of the friction material used in the lined clutch plates inside a given automatic transmission. So if a particular transmission calls for a specific type of fluid, that is the fluid you must use.

This is little different than engine oil which has viscosity ratings that vary based on intended usage as well as engineering parameters. Most OEMs base their recommended viscosity per bearing clearances. However, as we have all seen, sometimes the recommended viscosity is not optimal and trades off protection a bit too much relative to what gains may be realized by using the rec’ed oil viscosity. I run 10W-40 in my LH6 5.3L even though it calls for 5W-30. I do this because I value bearing protection over other considerations.

However I run Dex6 synthetic in the 6L80 it’s equipped with because that is what the friction material was designed to work with. Using other fluid wont allow it to work optimally (in fact may be severely harmful for the unit, depending on what’s put in).

Thanks for the reply.
Far be it for me to question someone who works on transmissions for a living with my limited knowledge, especially when it comes to tranmissions.
That said, as you might imagine I have spoken to guys who work on them exclusively, and they have differening points of view.

I will post a video of 8 different ATF fluids that were evaluated, and the AC Delco and the Toyota brands consistantly came in last place.

Also, what is your view on the GM bypass valve which purpose seems to be to get the fluid as hot as quickly possible, then keep it at 196 or above for the rest of your trip?

Lastly, while only a comparative analogy, if GM would put CAFE above lubrication and wear protection with their oil, why would you trust them not to do the same with their ATF to help bump the CAFE?

 

[tom3]

From what I've read the transmissions are pretty reliable, until the torque converter lockup clutch fails and puts shrapnel all though the unit. I did put a lower temp. control valve on my 6l trans. But I've never seen 190 degrees even in huge traffic jams going around Atlanta in the summer. But I also agree that DexVI seems to be pretty thin.

 

[jerry455]

Dex 6 is not as thin as ULV. ULV looks like pink water. I agree it seems as it is too thin but that is the speced fluid. I am not sure what engine you have where you are seeing 196 but my 2021 6.2 never seems to get that warm unless towing. Fluids that are too cold are not good either. The cooling systems seem very well designed. A lot of people seem to think they need to keep trans fluid at 150* and remove the thermostat to run as cool as possible, I don't think that is a good idea especially where you get cold temperatures. I am wondering if the ULV is wearing out and requires more frequent fluid changes. You have to shake it up before you put it in the trans.

 

[Marky Dissod]

... if they did that with motor oil, who is to say they didn't also do it with transmission ATF viscosity for the same reason?

Of course they did, CAFE hits every automaker with a perverse incentive: to squeeze out every last theoretical MpG, even at the cost of durability / longevity.

The measurement of Kinematic Viscosity is higher with thicker viscosity and the lower it goes, the thinner and less resistance it provides which also increases fuel mileage.
Don't get me wrong, I like better fuel economy as well, but engine/transmission protection and longevity is far more important to me,
and failure of either will result in a much greater cost than the couple of extra miles per thankful.

If it cost 3-4MpG, but extended the life of your engine past 250,000 miles and doubled the average life of your transmission, of course you'd accept that,
without question or reservation - otherwise you'd've leased it instead of buying it.

Additionally, it has always made me wonder why the temperatures of our GM transmissions be it the 6 - 8 - and now 10 speeds run consistently hot,
despite many of us having towing packages, which means individual coolers for our trannys.

Yes, this ATF temp chart is about Dex3, but I defy anyone to explain how the principles of this chart should be ignored for younger ATF formulations:
Dexron3 ATF temp behavior
176°F / 80°C . . . . 64,000-96,000 Miles ... Ideal Automatic Transmission Fluid Temp
194°F / 90°C . . . . 32,000-48,000 Miles ... Max Recommended Sustained ATF Temp
212°F / 100°C . . . 16,000-24,000 Miles ... MpG improves, Pressure Drops, longevity / durability decreases
(GM prefers ATF hotter to eke out another MpG or two, at the cost of durability / longevity)
230°F / 110°C . . . . 8,000-12,000 Miles ... Varnishes Form
257°F / 125°C . . . . . 4,000-6,000 Miles ... Seals Harden
275°F / 135°C . . . . . 2,000-3,000 Miles ... Clutches Slip
293°F / 145°C . . . . . 1,000-1,500 Miles ... Oil forms carbon, seals and clutches burn

Recently speaking to a transmission guy, he said heat and friction are killers of transmissions, just like it is with engines.
He explained that GM wants the ATF to heat up as quickly as possible to help thin out the viscosity for the same aforementioned CAFE reason.
Thus they use the bypass valve which restricts the ATF from going thru the cooler until it reaches around 196F. That means your temp once at the designated point is not going to drop back down below it.
As a bonus, if the bypass gets stuck closed and the ATF cannot get to the trans cooler, you could wind up with too hot a transmission and damage it.

If that bypass gets stuck, best case scenario: you're prematurely and very rapidly aging the ATF, hurry up and replace - or delete - the bypass.

 

[15burban]

Here's my thoughts on transmission fluid temperature. If the hottest fluid is in the torque converter where is the temperature sensor? It's not in the torque converter. I believe for the 6l80e it's in the valve body area. So whatever your reading temperature wise there's fluid that's hotter then the reading. Maybe it doesn't make a difference since the trans pumps a lot of fluid.

Either way some fluid gets replaced in both of my automatic equipped vehicles every year. Both of our automatics have their trans thermostat deleted. The 15 suburban will get up to 120-130 temps when it's 0 degrees out on a longer trip. Not apples to apples but my truck 16 ram 2500 won't hit 100 degrees when it's 0 degrees out. I don't think it gets above 100 degrees from December til March to tell you the truth. My truck (ram) is mainly used for short trips all under 25 minutes. Mostly 7 mile round trip dump runs once a week. After the trans hits 70 degrees there's no difference in shifting between 70 or the 140 or so it runs in the summer. Now maybe for racing purposes there might be some differences where every .10th of a second counts. But for day to day I don't see the cold temps hurting anything.

 

[Vector]

Thanks for the replies thus far.

I have a bunch of questions and observations.

1) Is anyone running other ATF than AC Delco when they flushed/changed it, and if so what did you choose and why?

2) Has anyone done the bypass, as I am serious thinking about doing so with this unit?

Since we are on the subject of transmissions, I noticed that while there has been regular maintenance with this used ESV that I have bought, there is no indication that the transmission fluid and filter was ever changed like the manual calls for at 45k, and every 45k after that. Note it says fluid and filter.
I called several Cadillac dealers in my area to see how much they charged, and was shocked to hear prices all in the $800-$1,000 range.
Even more surprising was that these were not change the fluid and replace the filter, rather it was to flush the system while leaving the filter in.

Now I am aware from having spoken to transmission guys over the years that the filter media is not like an oil filter, and only designed to catch large particulates, and may help to save it from a catastrophic failure in those situations.
Thus most have said it is not important to change it, but it is very important to change the fluid.

3) My question is, if the service manual calls for a fluid and filter replacements every 45k, why are Cadillac dealers not changing both the fluid and filter as part of their routine transmission service?

4) Also, if you are still under warranty, and your transmission dumps out, is not having the filter changed as part of the transmission service going to void the warranty, considering that none of the Cadillac dealers service departments change the filter as part of their routine?

Additionally, one of the dealers said the flush would be about $600 which while expensive, would be less than the others by $200-$400 less.
However, the service manager pointed out that it "may" also need to be reprogrammed after the flush, and that would run an additional $200

5) Have any of you ever heard of a reprogramming of our transmissions after a service, be it a flush or change including the filter?

6) Since these transmissions are on other trucks be it the 6.2 or the 3L, can they do just as good a job on servicing the transmissions as the Cadillac dealers, maybe at a lower cost?

 

[Tonyrodz]

Thanks for the replies thus far.

I have a bunch of questions and observations.

1) Is anyone running other ATF than AC Delco when they flushed/changed it, and if so what did you choose and why?

2) Has anyone done the bypass, as I am serious thinking about doing so with this unit?

Since we are on the subject of transmissions, I noticed that while there has been regular maintenance with this used ESV that I have bought, there is no indication that the transmission fluid and filter was ever changed like the manual calls for at 45k, and every 45k after that. Note it says fluid and filter.
I called several Cadillac dealers in my area to see how much they charged, and was shocked to hear prices all in the $800-$1,000 range.
Even more surprising was that these were not change the fluid and replace the filter, rather it was to flush the system while leaving the filter in.

Now I am aware from having spoken to transmission guys over the years that the filter media is not like an oil filter, and only designed to catch large particulates, and may help to save it from a catastrophic failure in those situations.
Thus most have said it is not important to change it, but it is very important to change the fluid.

3) My question is, if the service manual calls for a fluid and filter replacements every 45k, why are Cadillac dealers not changing both the fluid and filter as part of their routine transmission service?

4) Also, if you are still under warranty, and your transmission dumps out, is not having the filter changed as part of the transmission service going to void the warranty, considering that none of the Cadillac dealers service departments change the filter as part of their routine?

Additionally, one of the dealers said the flush would be about $600 which while expensive, would be less than the others by $200-$400 less.
However, the service manager pointed out that it "may" also need to be reprogrammed after the flush, and that would run an additional $200

5) Have any of you ever heard of a reprogramming of our transmissions after a service, be it a flush or change including the filter?

6) Since these transmissions are on other trucks be it the 6.2 or the 3L, can they do just as good a job on servicing the transmissions as the Cadillac dealers, maybe at a lower cost?

Did you ask why the trans would/might need to be reprogrammed after a flush? I don't understand the logic behind that.

 

[Vector]

Dex 6 is not as thin as ULV. ULV looks like pink water. I agree it seems as it is too thin but that is the speced fluid. I am not sure what engine you have where you are seeing 196 but my 2021 6.2 never seems to get that warm unless towing. Fluids that are too cold are not good either. The cooling systems seem very well designed. A lot of people seem to think they need to keep trans fluid at 150* and remove the thermostat to run as cool as possible, I don't think that is a good idea especially where you get cold temperatures. I am wondering if the ULV is wearing out and requires more frequent fluid changes. You have to shake it up before you put it in the trans.

I live in a very warm climate, so the things people in the north/cold climate worry about is not a concern for us down south. Even in the cold months my trans temp gets to 60 while idling for just a few minutes, and is good to go. If global cooling gets worse I might have to rethink things.
I do some towing, be it a trailer or boat, and when I see my trans temps getting into the 210+ range I will occasionally stop to let it cool down some. I really shouldn't have to and with the bypass (if I decide to do it) I wont have to worry about it.

 

[Vector]

Did you ask why the trans would/might need to be reprogrammed after a flush? I don't understand the logic behind that.

No, as the woman service writer said her top trans fluid tech told her "it might" need a reprogram, so she obviously didn't know.
I am hoping someone like Nick Transmissions might know, and I am going to ask around to see if others are doing it.

I am tempted to go somewhere other than the dealer, not only for a lower cost, but if I want to put in a better ATF and/or the bypass, the dealership won't do it.
Plus at this point if I want to have the filter changed (if they drop the pan to flush it which I am not sure if that is part of the procedure), why not put in a new $15 filter since it is only two bolts and couldn't add much labor time.

 

[Tonyrodz]

No, as the woman service writer said her top trans fluid tech told her "it might" need a reprogram, so she obviously didn't know.
I am hoping someone like Nick Transmissions might know, and I am going to ask around to see if others are doing it.

I am tempted to go somewhere other than the dealer, not only for a lower cost, but if I want to put in a better ATF and/or the bypass, the dealership won't do it.
Plus at this point if I want to have the filter changed (if they drop the pan to flush it which I am not sure if that is part of the procedure), why not put in a new $15 filter since it is only two bolts and couldn't add much labor time.

I agree with you 100%.

 

[jfoj]

The filter is not $15, a genuine AC Delco trans filter is around $70 as I recall if you shop it.

 

[2024 White Tahoe]

Thanks for the replies thus far.

I have a bunch of questions and observations.

1) Is anyone running other ATF than AC Delco when they flushed/changed it, and if so what did you choose and why?

2) Has anyone done the bypass, as I am serious thinking about doing so with this unit?

Since we are on the subject of transmissions, I noticed that while there has been regular maintenance with this used ESV that I have bought, there is no indication that the transmission fluid and filter was ever changed like the manual calls for at 45k, and every 45k after that. Note it says fluid and filter.
I called several Cadillac dealers in my area to see how much they charged, and was shocked to hear prices all in the $800-$1,000 range.
Even more surprising was that these were not change the fluid and replace the filter, rather it was to flush the system while leaving the filter in.

Now I am aware from having spoken to transmission guys over the years that the filter media is not like an oil filter, and only designed to catch large particulates, and may help to save it from a catastrophic failure in those situations.
Thus most have said it is not important to change it, but it is very important to change the fluid.

3) My question is, if the service manual calls for a fluid and filter replacements every 45k, why are Cadillac dealers not changing both the fluid and filter as part of their routine transmission service?

4) Also, if you are still under warranty, and your transmission dumps out, is not having the filter changed as part of the transmission service going to void the warranty, considering that none of the Cadillac dealers service departments change the filter as part of their routine?

Additionally, one of the dealers said the flush would be about $600 which while expensive, would be less than the others by $200-$400 less.
However, the service manager pointed out that it "may" also need to be reprogrammed after the flush, and that would run an additional $200

5) Have any of you ever heard of a reprogramming of our transmissions after a service, be it a flush or change including the filter?

6) Since these transmissions are on other trucks be it the 6.2 or the 3L, can they do just as good a job on servicing the transmissions as the Cadillac dealers, maybe at a lower cost?

#3.

GM does not recommend flushing transmissions, except the new Corvette which has a specific process.

Dealers make a lot of money using the BG flushing machine. The process to change the transmission fluid and filter is more labor intensive, so they steeer customers to the flushing process (which is a cash-cow for them).

Also - I have never heard of a transmission requiring reprogramming after a service (other than rebuild or replacement). I suspect the dealer is low-balling you on the price, then will add-on the reprogramming.

 

[jerry455]

GM had a large service bulletin service with the 8 speed trans in the Colorado, maybe other vehicles with the same trans also, I had a 2018 Colorado. The first version of the Mobil trans fluid absorbed moisture. There was a service bulletin about flushing approximately 20 quarts of the upgraded Mobil, blue label, through a trans flush procedure. I don't see how it would hurt anything the way GM did it. It would be easy to do. It is not a reverse flush which used to be a problem.

 

[B-train]

GM had a large service bulletin service with the 8 speed trans in the Colorado, maybe other vehicles with the same trans also, I had a 2018 Colorado. The first version of the Mobil trans fluid absorbed moisture. There was a service bulletin about flushing approximately 20 quarts of the upgraded Mobil, blue label, through a trans flush procedure. I don't see how it would hurt anything the way GM did it. It would be easy to do. It is not a reverse flush which used to be a problem.

That is correct about the first fluid GM used. The suspended moisture would cause the TC to grab instead of glide like it should.

I had this done on my 2017 Denali. Worked awesome and done correctly is nothing to worry about. I've had 3 transmission flushes and 2 filter changes on my 2017 - 40k intervals. Runs/shifts great with 180k thus far.

 

[Vector]

GM had a large service bulletin service with the 8 speed trans in the Colorado, maybe other vehicles with the same trans also, I had a 2018 Colorado. The first version of the Mobil trans fluid absorbed moisture. There was a service bulletin about flushing approximately 20 quarts of the upgraded Mobil, blue label, through a trans flush procedure. I don't see how it would hurt anything the way GM did it. It would be easy to do. It is not a reverse flush which used to be a problem.

Why was the dealer using Mobil instead of the AC Delco ATF ?
Personally I am considering using Amsoil Signature Series ULV

 

[Marky Dissod]

The first version of the Mobil trans fluid absorbed moisture. There was a tech service bulletin about flushing approximately 20 quarts of the upgraded Mobil1, blue label,
through a trans flush procedure.

That is correct about the first fluid GM used. The suspended moisture would cause the TC to grab instead of glide like it should.

The GM OE factory / showroom floor ATF was NOT Mobil1.

 

[TxVet33]

Did you ask why the trans would/might need to be reprogrammed after a flush? I don't understand the logic behind that.

$$$$$$$$$$$$$$$$$$

 

[Rygrego]

Years ago before synthetic oil, I was running 20W50 in most of my motors (some HP applications) and never thought about fuel efficiency, I just wanted the most protection possible. Never did I have an engine failure.

In recent years GM has told us we MUST use the every thinning oil to maintain our warranty, and most of us presumed it was best for the engines health, as why else would they say the warranty would be invalidated.
Yet today we have come to find out those mandates were not based on our engines best interest, protection, nor longevity. Rather it was to meet stringent CAFE standards, and thinner motor oil with less resistance meant their vehicles got a slight improvement in fuel efficiency, thereby saving them millions of dollars. Thus they had us using practically water with 0w20, and their recall protocol now is to use 0w40.
Keep in mind that in Europe and other countries the exact same engine mandates 5w30 because they do not have the CAFE standards over there.
They likely also calculated that when the engines fail it will typically be after the warranty, and then depending on how much the repairs and future problems would cost, they could sell you a new vehicle.

So, if they did that with motor oil, who is to say they didn't also do it with transmission ATF viscosity for the same reason. The measurement of Kinematic Viscosity is higher with thicker viscosity and the lower it goes, the thinner and less resistance it provides which also increases fuel mileage.
Don't get me wrong, I like better fuel economy as well, but engine/transmission protection and longevity is far more important to me, and failure of either will result in a much greater cost than the couple of extra miles per thankful.

Additionally, it has always made me wonder why the temperatures of our GM transmissions be it the 6 - 8 - and now 10 speeds run consistently hot, despite many of us having towing packages, which means individual coolers for our trannys.
Recently speaking to a transmission guy, he said heat and friction are killers of transmissions, just like it is with engines.
He explained that GM wants the ATF to heat up as quickly as possible to help thin out the viscosity for the same aforementioned CAFE reason. Thus they use the bypass valve which restricts the ATF from going thru the cooler until it reaches around 196 degrees. That means your temp once at the designated point is not going to drop back down below it.
As a bonus, if the bypass gets stuck closed and the ATF cannot get to the trans cooler, you could wind up with too hot a transmission and damage it.

My question to you'll is now that you don't trust GM to do what is best for the consumer regarding motor oil because of CAFE, should we trust them with the ATF mandates using their AC Delco Dexron ATF vs. another brand and/or viscosity?
If you are using something else what brand/viscosity are you using?
Also, how many of you have done the bypass valve block kit, or even an aftermarket free flow valve which keeps the temperatures much lower under all conditions?

3 years ago GM revised the transmission thermostat temperature from the 176 degree one to 154 degree (TSB GM # 21-NA-199) . I changed to the new thermostat (less than $60) and added a Mishimoto trans cooler and my trans temp rarely gets to 170 even towing in Arizona summer heat.