Trans temps

BULLSEYE · April 9, 2019

I have a 2018 Silverado crew cab. Level kit with 33” tires. Hwy driving not towing anything I’m getting temp from 192-194 in 85* temps. Seems a lil high.

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CKNSLS · April 9, 2019

7 minutes ago, BULLSEYE said:

I have a 2018 Silverado crew cab. Level kit with 33” tires. Hwy driving not towing anything I’m getting temp from 192-194 in 85* temps. Seems a lil high.

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In the last couple of years they put in a thermostat in these transmissions that makes them run warmer. There are youtube videos that show how to "delete" this thermostat. However-IMHO the engineers who designed the truck knew what they are doing. Also-the Dex 6 is rated to at least 275 degrees. If you do a google search this forum will come up with information on the above.

Edited April 9, 2019 by CKNSLS

newdude · April 9, 2019

Temp sounds normal. They run like that stock. Thermostat opens around 190-194 degrees to flow to the trans cooler and aux cooler. Higher operating temp = less friction loss = better fuel economy.

Edited April 9, 2019 by newdude

btj_z71 · April 9, 2019

Its totally normal, even with the HD cooling system.

Grumpy Bear · April 9, 2019

192 F is the thermostat set point. The factory thermostat does not have a minimum flow bypass so nothing flows to the cooler(s) until it opens. That first shot of fluid is a shock to the system (winter). With the thermostat in cold climates it will actually delay fluid heat up.

Doesn't matter how good you believe the fluid is, the seals start to harden by 220 F and will be toasted by 295F as will be the clutch plates . I'm not posting the fluid life charts again. Fluid temperatures between 100F and 165 F will keep the fluid and everything it touches happy a very long time. The 6L80E lived without a thermostat for years and worked just fine. The factory cooler(s) have enough capacity to keep it cool with a simple thermostat delete OR and after market replacement with a lower set point. Improved racing has several options in example, unless your towing the max under extreme conditions.

As an engineer I will tell you engineers don't always do what is right. If they like getting paid they do what their told. Just say' n.

redwngr · April 9, 2019

I don't know how warm the GM 6 speed behind the 6.0L runs, but I've always found it interesting that the Allison, runs MUCH cooler than the transmissions in the the 1500's.

I've run more than one of each, under similar conditions.

CKNSLS · April 9, 2019

That fluid chart that has been posted ten thousand times on the Internet is outdated- even with the new " flashy "version. The transmission and fluid are made to take higher temps that what you mentioned. It's your truck and my truck-you can believe what you want.

Edited April 9, 2019 by CKNSLS

truckguy82 · April 9, 2019

48 minutes ago, Grumpy Bear said:

192 F is the thermostat set point. The factory thermostat does not have a minimum flow bypass so nothing flows to the cooler(s) until it opens. That first shot of fluid is a shock to the system (winter). With the thermostat in cold climates it will actually delay fluid heat up.

Doesn't matter how good you believe the fluid is, the seals start to harden by 220 F and will be toasted by 295F as will be the clutch plates . I'm not posting the fluid life charts again. Fluid temperatures between 100F and 165 F will keep the fluid and everything it touches happy a very long time. The 6L80E lived without a thermostat for years and worked just fine. The factory cooler(s) have enough capacity to keep it cool with a simple thermostat delete OR and after market replacement with a lower set point. Improved racing has several options in example, unless your towing the max under extreme conditions.

As an engineer I will tell you engineers don't always do what is right. If they like getting paid they do what their told. Just say' n.

My trans thermostat has a little flow before opening. I have felt the lines atleast 50 times trying to diagnose a problem with the thermostat. Before and after getting it repaired.

before it opens, the input to the cooler is hot, about as hot as the indicated trans temp. The output to the cooler is cold, ambient temp. When the thermostat opens, both lines are hot.

The only explanation for this is that the line flows a little before it opens. Small enough flow that it’s ambient when it leaves the cooler. But it still flows.

This is a 2014 6l80.

Jacoby · April 9, 2019

Temps are perfectly normal. Mine will run 195* towing or not. Occasionally when towing i'll hit 200*

CKNSLS · April 9, 2019

16 minutes ago, Jacoby said:

Temps are perfectly normal. Mine will run 195* towing or not. Occasionally when towing i'll hit 200*

Agreed. To say that by 220 the transmission will "melt down"-that would allow only a 25 degree separation between "normal" (when thermostat opens) and self destructing-which that amount of variance is ludicrous. This is not taking in to account towing temps. And I'M NOT AN ENGINEER.

Edited April 9, 2019 by CKNSLS

MikeNH · April 9, 2019

3 hours ago, redwngr said:

I don't know how warm the GM 6 speed behind the 6.0L runs, but I've always found it interesting that the Allison, runs MUCH cooler than the transmissions in the the 1500's.

I've run more than one of each, under similar conditions.

The Allison is a totally different transmission and it uses a different fluid.

Crobinson16 · April 9, 2019

Is there a lower thermostat to install or a different way other than tapping and treading in a plug. I'd like to come up with something that can be easily changed or not easily detectable for any type of warranty work.

NE18 · April 10, 2019

I tow a 3500lbs camper and the temp is around 200. It has reached 208 while towing in traffic.

redwngr · April 10, 2019

1 hour ago, MikeNH said:

The Allison is a totally different transmission and it uses a different fluid.

Hmmm...who knew...

I always thought the Dex VI in the Allison was the same Dex VI as the 6 speeds....

(yes, the new 8 speed uses a different fluid - the new Dex HP)

Not that I was suggesting that the temps being discussed are an issue -- and I don't think that they are.

Just an observation about the different operating temps.

Edited April 10, 2019 by redwngr

Grumpy Bear · April 10, 2019

2 hours ago, CKNSLS said:

Agreed. To say that by 220 the transmission will "melt down"-that would allow only a 25 degree separation between "normal" (when thermostat opens) and self destructing-which that amount of variance is ludicrous. This is not taking in to account towing temps. And I'M NOT AN ENGINEER.

Not what I said, is it? I said seals START to harden at 220F.

Run it at 500F if you like. Why would I care?

3 hours ago, truckguy82 said:

My trans thermostat has a little flow before opening. I have felt the lines atleast 50 times trying to diagnose a problem with the thermostat. Before and after getting it repaired.

before it opens, the input to the cooler is hot, about as hot as the indicated trans temp. The output to the cooler is cold, ambient temp. When the thermostat opens, both lines are hot.

The only explanation for this is that the line flows a little before it opens. Small enough flow that it’s ambient when it leaves the cooler. But it still flows.

This is a 2014 6l80.

If there is, then it isn't seating. There is NO PROVISION in the Stat for a min flow. It's a 45* spring loaded seat on seat. I've take several apart for modification. It will not pass air so it wont' pass fluid. But whatever. Broke is the new normal.

3 hours ago, CKNSLS said:

That fluid chart that has been posted ten thousand times on the Internet is outdated- even with the new " flashy "version. The transmission and fluid are made to take higher temps that what you mentioned. It's your truck and my truck-you can believe what you want.

Again, didn't say it wont take it. It isn't a matter of taking it once or twice or thirty dozen times. It's a matter of cumulative damage. That chart is what it is. Every major trans reman, stock or performance and cooler company still use it. B & M, TransGo, TCI. PAC, SONNAX, Circle D...…There is no magic. NASA didn't build this box.

Not even GM evidently is comfortable with running a continuous 220F + or they wouldn't put a cooler on and even more cooler of the full Monty tow packages. Set alarms for temperature and limp modes. But hey, not being an engineer I'm sure you know better than the collective industry. You are right. My truck and it will never see those temperatures. Not even for a minute.

Mobil makes claim for 500F for their Group III fluids. Not even a full on Polyol Ester Jet Turbine oil will take 500 F without some serious add pack heat enhancement. Your not going to find it in a $12 a quart fluid.

What is true is ALL manufactures are under the gun for MPG numbers and waste reduction. Bring on the heat....The guts in this current 6L80E are evolving granted.

For as much hate as the six speed gets for being a stumbling drunk I'm at a loss to explain why anyone, forum members, would do what they can to make it's life even shorter.

This is just for fun: Something I ran across. Cut and Paste.

Intermittent Harsh Downshift, Chuggle or Shudder During Deceleration 5.3L Tahoe, Suburban, C/K Trucks Customer complaint may be harsh forced downshifts or the chuggle/shudder during a coast down intermittently. This is considered “Normal” with this powertrain package. It is a self test for the O2 sensors. Test runs with the vehicle speed above 45 MPH (72 kph) in 6th gear with the TCC applied. The ECM drives the fuel system rich and then into deceleration fuel cutoff mode (shutting the injectors off) to check the system. Test will end during the deceleration and fuel is restored. (This typically causes the Shudder/Chuggle shift feel in the vehicle). Aggressive throttle response during this system check mode will cause the vehicle to have a “Harsh” downshift (this happens because the TCC remains applied during the test). If the test runs while in 5th gear, the TCC will not be applied and the complaint will not likely occur. Note: The test is designed to occur one time per key cycle, but can run up to 10 times if aborted due to throttle input.