2020 Ram 1500 trans temps mod

[Tyler-98-W68]

Sounds like a good idea maybe let stellantis know how to program their PCMs....

[Tcmustang93]

Originally Posted by aircommuter

You just don’t realize that there is an issue. I have been in the automotive business for over 50 years and I still follow and subscribe to all trade publications.
Designed temperature has a purpose, lower isn’t always better. It is just a mindset of the inexperienced.

Very True aircommuter. I used to try to keep my trans temps down to 160-175 range It bothered me to see 190 or more. When my trans went out at 50,000 the dealership scolded me for the aftermarket trans cooler. And said to perform to spec the temp
Needed to be at 190. And removed my after market cooler. Now at 186,000 miles I have change the fluid two more times but it pulls great and stays at 190 degrees.

[mikeyk101]

Although this is almost apples to oranges, the GM 6L80 transmissions initially came without thermostats. I am not certain but think around 2014 for at least Silverados and Sierras, they added the thermostat that was a 190⁰ thermostat. I was told that the biggest reason was to get transmission temps warmer and that was to help with slightly increasing fuel efficiency to satisfy the EPA. But it has turned into an issue as transmission failures have dramatically increased and GM in many cases has refused to issue a recall. There have been lawsuits filed as a result of this. There is a mod that many have done where you remove the transmission thermostat, open it up and flip what is called "the pill" then reinstall. This allows trans fluid to always be flowing through the condenser up front of the radiator instead of only happening once the 190⁰ happens. Just recently, GM has a TSB out as well as an updated 154⁰ transmission thermostat. If a customer brings in a Silverado or Sierra with any kind of transmission complaints, one of the first things done is to replace the existing transmission thermostat with the updated on. It does not require any additional programming to the transmission or BCM.

I have seen some posts on this thread talking about the 190⁰ being the most efficient. It may be as far as eaking out a bit more fuel efficiency but even GM has seen that this is at the cost of ruining transmissions. Running transmissions at cooler than 190⁰ only makes sense.

[Tyler-98-W68]

Right from ZF themselves the 8 Speed is designed with a normal operating temp of 190, it has nothing to do with fuel economy

[aircommuter]

Originally Posted by mikeyk101

Although this is almost apples to oranges, the GM 6L80 transmissions initially came without thermostats. I am not certain but think around 2014 for at least Silverados and Sierras, they added the thermostat that was a 190⁰ thermostat. I was told that the biggest reason was to get transmission temps warmer and that was to help with slightly increasing fuel efficiency to satisfy the EPA. But it has turned into an issue as transmission failures have dramatically increased and GM in many cases has refused to issue a recall. There have been lawsuits filed as a result of this. There is a mod that many have done where you remove the transmission thermostat, open it up and flip what is called "the pill" then reinstall. This allows trans fluid to always be flowing through the condenser up front of the radiator instead of only happening once the 190⁰ happens. Just recently, GM has a TSB out as well as an updated 154⁰ transmission thermostat. If a customer brings in a Silverado or Sierra with any kind of transmission complaints, one of the first things done is to replace the existing transmission thermostat with the updated on. It does not require any additional programming to the transmission or BCM.

I have seen some posts on this thread talking about the 190⁰ being the most efficient. It may be as far as eaking out a bit more fuel efficiency but even GM has seen that this is at the cost of ruining transmissions. Running transmissions at cooler than 190⁰ only makes sense.

Different, clutches, different oil, different shift application timing. Just different. Like you said apples to oranges.

[mikeyk101]

I know nothing about ZF transmissions so that may just be the case for them. Like I mentioned, it is probably apples to oranges but for the General Motors 6L80, it has not been the case. This is why many of the transmissions that have the original 190⁰ thermostats are now going to be retrofitted with 158⁰ thermostats if taken to dealer with any complaints. The previous generations using the 6L80 did not use a thermostat and had less failures. The newer vehicles are now already being fitted with the 158⁰ trans thermostat.

[1100mike]

I live in a place where we experience winter for several months. Before I bypassed the trans thermostat I drove it for a couple years. Often my transmission would go for a month or more in frigid temps and never get up to the 172 degree temp that opened the Tstat for the cooler. So, was I damaging my transmission in those short, cold weather, drives? I just turned 100k on my Ram. Changed the fluid twice. It's a popular modification on the Ram forum for the heavy duty trucks. Have yet to see a negative review or failure because of it..

[JCR]

Doing this mod will hurt your vehicle over time. Engines and transmissions are designed with certain heat parameters and modifications will only hurt the overall performance and longevity . The computers in these vehicles are so very sophisticated that they determine the proper algorithm for the operating condition.Todays engines require more heat for efficient operation. Be careful and the mindset that cooler is better can actually be harmful over time.. especially in winter environments.

[1100mike]

So, winter driving where your trans temps may not get up to factory requirements "may" damage your transmission over time? Got it..

[JCR]

Originally Posted by 1100mike

So, winter driving where your trans temps may not get up to factory requirements "may" damage your transmission over time? Got it..

The computer will initiate the proper algorithm for the climate and temperatures.These engineers test these vehicles in grueling extremes both frigid and hot hot desert conditions and build their computers to manage the engine in best possible way under its environment. When you screw around with it everything and all that engineering goes away and you are on your own.
.

[1100mike]

I'll just let the computer do it's algorithms on my cooler running temperatures and take my chances on my out of warranty vehicle. Thank you for your input. If my transmission fails due to a too cold operating temperature, I'll be sure to let everyone know..

[Jay2504]

Mikeyk101, could you please post the TSB number for the transmission thermostat bulletin and/or the part number for the 158 degree thermostat. I used to tow with our 2014 Silverado. I added an extra cooler in series but left the stock thermostat alone, thinking of getting the transmission warmer in the wintertime but having a tighter upper limit when towing in the summer. Before I installed the extra cooler, I once hit 239 degrees going up a long winding hill! Now we tow with a 2020 2500hd, that gets the transmission to around 195 also but has a built in extra cooler. It also uses a clutch fan instead of PCM controlled electric fans. Thanks in advance. Jay

[Dragonmaster]

All this talk of the garbage GM transmissions based on a 90’s design with tweaks year over year vs a ZF transmission engineered in 2010ish. I’ve personally had three GM transmissions take a dump before I hit 61k on a single truck, the last one had me sell the truck and go to Ram as it was 500km over warranty and they gave me a compassionate care replacement. Never had the same issue with MUCH heavier towing on Ram. I tow through the Rockies and have seen temps hit 210, but never over going up many 10-12% grades in summer. I trust this ZF that has made it 165000k before trade in on my last truck and now 12k on my new truck. My previous GM had already dumped a transmission at 6k. End of comparison.

[Cost4133]

Originally Posted by Lawrosa

They should kick on for coolant temp only as that runs hotter then the trans. even in stock config.

your trans temp 100% can be higher than the coolant temp happens all the time when you are working a truck especially in the hills.

Therefore your PCM is monitoring all sorts of conditions to control the fan: Trans temp, coolant temp, a/c switch, EGR valve (diesels).

I know back in the days of regular 4 spds (4L60,4L80, 4r100, 47/48RE) general rule of thumb was you wanted to keep your trans temp below 100* over ambient temp.

But the more modern Trans (5r110, 68rfe, aisin, allison, ZF8hp, 6r140) have more cooling capability (in general) but also use thermostats to get them up to temp that they were designed by the engineering teams to operate at. That means the clutch packs were designed for a certain fluid viscosity/temp.

[mrfikser]

Lets see here...190f is toooo hot for a trans, even though the fluid in it doesn't reduce its lubrication etc abilities until well above 250f...who decided 190f is too hot. Where running below around 190f will greatly reduce the evaporation of any water that WILL accumulate in the oil...The whole logic of cooler is better is flawed (below ideal running temperature)..Now, if the changes made were to keep a harder working transmission from exceedind 190f, that would make sense, but that is not happening here, the modification only lowers the minimum temperature...Using the same logic I should remove the engine thermostat because 'colder is better all the time'.

[mikeyk101]

Originally Posted by Jay2504

Mikeyk101, could you please post the TSB number for the transmission thermostat bulletin and/or the part number for the 158 degree thermostat. I used to tow with our 2014 Silverado. I added an extra cooler in series but left the stock thermostat alone, thinking of getting the transmission warmer in the wintertime but having a tighter upper limit when towing in the summer. Before I installed the extra cooler, I once hit 239 degrees going up a long winding hill! Now we tow with a 2020 2500hd, that gets the transmission to around 195 also but has a built in extra cooler. It also uses a clutch fan instead of PCM controlled electric fans. Thanks in advance. Jay

Here is one post with the info. I haven't been able to find the actual bulletin 21-NA-199 but this has the information about it:
https://gm-techlink.com/?p=15389


This thread may also be of interest to you:

https://www.gm-trucks.com/forums/top...omment=2556081

[mikeyk101]

Just to add, the trans thermostat on the GM trucks is easily a do it yourself project and only takes a couple minutes tops to do it. It takes a 10mm socket and a 13mm socket. Just need a pan underneath to catch the little amount of trans fluid that will leak out. Not even enough to worry about having to replace it. And pay attention to the transmission lines as each has a small o-ring on the ends and you don't want to lose them.

The new part number on the transmission thermostat is 86774933 and its a good idea to also replace the seal at same time part # 23135703
It cost just under $70 shipped for both when I ordered them from gmpartsgiant.

[Lins]

Originally Posted by aircommuter

the oil is supposed to be up to operating temperature so the viscosity is correct for proper shifting. They wouldn’t go to that expense for nothing. Thicker oil between clutch plates causes engagement delay. The people that do these mods have likely never been in the transmission business.

x2!

Originally Posted by Tyler-98-W68

As someone who tunes ZF transmissions you are demonstrating you don't know much about them. 190f trans temp is normal and is completely within spec from ZF, your opinion doesn't change facts



The fans aren't even programmed to come on based on trans temp until 212f, yet you think 190f is too hot?

You simply can't compare a 4L60 and a ZF8 at all......

Nice explanation, and showing what's happening behind the scenes.

[Lawrosa]

You guys make me laugh..

ZF fluid has a flat viscosity curve.. You guys dont seem to know much. The engineers want the high temps for efficiency fuel savings. I could give two $#$% about that.

Its not a lifetime fluid. I tow with this rig. Temps 230-240-200-210-220 etc etc are not acceptable to me..

educate yourself. I got 25k miles and the fluid already looks and smells horrible. Mostt likely from the heat.

Its getting changed out after the new year..



https://aftermarket.zf.com/remotemed...fluid-8-it.pdf

[Lawrosa]

Trust me and i pulled some fluid putting the t stat mod in.

It does not look like the fluid on the left.