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2023 GMC Sierra 3500HD 6.6L Gas/6 Speed - Trans Temps?

SoCal Angler

By SoCal Angler
in 6.6L Gas V8 (L8T)

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SoCal Angler Enthusiast

SoCal Angler

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Being that the truck is new, and it does have the 158F new TBV, I can only try and get dealer to do what they can.  It's under warranty so I can't change parts on my own and void warranty.  Let's see if they use their scan tool and see at what temps the TBV fully opens.  That should explain everything.  

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Another JR
Another JR

I went in circles with the dealer and with GM customer support and they refused. I pointed to that wording but they (GM) said there still needs to be a customer complaint about the way the transmissio

newdude
newdude

GM being GM, the TBV temp on 2020-2021 HD was factory 90C/194F.  After all the issues broke out with converters and failures on 6L80/90 units, they revised the TBV temp to 70C/158F.  All production HD

Pryme
Pryme

Well I’m glad I have the 158 and would make the change if I had the 194. Just seems better to run a bit cooler for longevity. Just my feeling on it. 

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Another JR Senior Enthusiast

Another JR

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Posted

The switchover was April 2021 about two weeks after my truck was built. I could not get the dealer or GM tech support to change the valve under warranty.
 

I haul a light truck camper and don’t tow heavy, and have never seen higher than about 205F. The majority of my driving it stabilizes between 189 and 196F, and goes a little above that on long climbs. 
 

So I’m planning to change out the valve myself immediately before I get the fluid changed by the dealer at 15k or 3 years, whichever comes first.  

  • Like 1
SoCal Angler Enthusiast

SoCal Angler

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Posted (edited)
15 hours ago, Another JR said:

The switchover was April 2021 about two weeks after my truck was built. I could not get the dealer or GM tech support to change the valve under warranty.
 

I haul a light truck camper and don’t tow heavy, and have never seen higher than about 205F. The majority of my driving it stabilizes between 189 and 196F, and goes a little above that on long climbs. 
 

So I’m planning to change out the valve myself immediately before I get the fluid changed by the dealer at 15k or 3 years, whichever comes first.  

I believe the TSB states GM must replace with new valve, even is customer concern can not de duplicated.  Perhaps you can try another dealer. 

 

I believe the powertrain warranty is 5 years/60K miles.  Will you be installing an OEM valve or after market, i.e., Superior Transmission Parts?  

Trans Bypass VALVE

 

BTW...I went with the 3500 as I too may get a truck camper one day. 8'-8.5'.  Maybe a pop up.  What camper do you have?

Edited by SoCal Angler
SoCal Angler Enthusiast

SoCal Angler

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Got an appt to take it in tomorrow to a dealer in my home town.  I showed the two TSBs when I went in person to make appt.  Service advisor said to bring them tomorrow when I drop off truck. I'll know more tomorrow.

 

BTW....took truck for a 45 mile drive today around town and highway.  One hour drive.  Ambient temps 90F.  Trans temps around 167-173 for 50 mins and then slowly climbed to 185 at the last 5 -10 mins of the trip.

Edited by SoCal Angler
newdude Senior Enthusiast

newdude

Posted
Posted
22 hours ago, SoCal Angler said:

Being that the truck is new, and it does have the 158F new TBV, I can only try and get dealer to do what they can.  It's under warranty so I can't change parts on my own and void warranty.  Let's see if they use their scan tool and see at what temps the TBV fully opens.  That should explain everything.  

 

 

The TBV can't be "read with a scan tool" to see when it opens.  If the TBV is functioning properly, it opens at 158F.  If there are other factors at play (traffic, high ambient temperatures, towing) those will all have an effect on what the ATF temp does beyond that full open 158F mark.  

 

 

25 minutes ago, SoCal Angler said:

Got an appt to take it in tomorrow to a dealer in my home town.  I showed the two TSBs when I went in person to make appt.  Service advisor said to bring them tomorrow when I drop off truck. I'll know more tomorrow.

 

BTW....took truck for a 45 mile drive today around town and highway.  One hour drive.  Ambient temps 90F.  Trans temps around 167-173 for 50 mins and then slowly climbed to 185 at the last 5 -10 mins of the trip.

 

 

Normal.  And they will tell you the same thing.  Normal.    

  • Like 2
SoCal Angler Enthusiast

SoCal Angler

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Posted (edited)
39 minutes ago, newdude said:

 

 

The TBV can't be "read with a scan tool" to see when it opens.  If the TBV is functioning properly, it opens at 158F.  If there are other factors at play (traffic, high ambient temperatures, towing) those will all have an effect on what the ATF temp does beyond that full open 158F mark.  

 

 

 

 

Normal.  And they will tell you the same thing.  Normal.    

  

 

Thanks.  Wrong of previous dealer to tell me they'll use a scan tool.

 

Since there is no tool to tell when it is fully open at 158F, how do they determine if it is properly functioning TBV?  Ex.  Bad TBV, not opening or intermittent opening at 158F, stuck TBV, etc.? 

I'm puzzled.

Edited by SoCal Angler
Pryme Senior Enthusiast

Pryme

Posted
Posted
40 minutes ago, newdude said:

 

 

The TBV can't be "read with a scan tool" to see when it opens.  If the TBV is functioning properly, it opens at 158F.  If there are other factors at play (traffic, high ambient temperatures, towing) those will all have an effect on what the ATF temp does beyond that full open 158F mark.  

 

 

 

 

Normal.  And they will tell you the same thing.  Normal.    

If his is normal is mine abnormal for never even getting to 167 in a normal driving situation which is the temp his started at?

  • Like 1
SoCal Angler Enthusiast

SoCal Angler

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1 minute ago, Pryme said:

If his is normal is mine abnormal for never even getting to 167 in a normal driving situation which is the temp his started at?

what is your ambient temp and driving conditions (hwy, city( ?

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
On 8/6/2023 at 5:25 PM, Grumpy Bear said:

Given the days temperatures it did pretty good. That said if were that hot ever day I'd be looking for additional cooler. 

 

 

 

I stand by this ^^^^ 

 

@newdude has nailed this. 

  • Like 1
newdude Senior Enthusiast

newdude

Posted
Posted
2 hours ago, SoCal Angler said:

  

 

Thanks.  Wrong of previous dealer to tell me they'll use a scan tool.

 

Since there is no tool to tell when it is fully open at 158F, how do they determine if it is properly functioning TBV?  Ex.  Bad TBV, not opening or intermittent opening at 158F, stuck TBV, etc.? 

I'm puzzled.

 

 

Stuck closed = Transmission overheat warnings real quick.  265F is the warning point.    

 

Stuck open = would take longer to heat up.  

 

 

  • Like 2
Another JR Senior Enthusiast

Another JR

Posted
Posted (edited)
10 hours ago, SoCal Angler said:

I believe the TSB states GM must replace with new valve, even is customer concern can not de duplicated.  Perhaps you can try another dealer. 

 

I believe the powertrain warranty is 5 years/60K miles.  Will you be installing an OEM valve or after market, i.e., Superior Transmission Parts?  

Trans Bypass VALVE

 

BTW...I went with the 3500 as I too may get a truck camper one day. 8'-8.5'.  Maybe a pop up.  What camper do you have?

I went in circles with the dealer and with GM customer support and they refused. I pointed to that wording but they (GM) said there still needs to be a customer complaint about the way the transmission is operating. The transmission was working fine, and I wasn’t going to lie to them. I just wanted the updated design. 
 

I plan to install the GM part with the 70 marking. 
 

I have a Four Wheel Camper Grandby (8 foot bed) front dinette model with most of the options. I did my own lithium solar and dc to dc charger installations to save money and get exactly what i wanted for my power system. It weighs about 1800 lbs fully loaded up for camping - 1700 on rear axle and 100 on front axle. So I’m at about 50% of the payload rating. I have no suspension mods except I took out the unneeded 5600 lb front camper springs i originally ordered and put in the base 5200 lb springs for my model. 
 

I wanted the 3500 payload because it allows me to tow a decent sized fishing boat with the camper on. 

56590F52-FBBD-48F2-A84D-D449676454FA.jpeg

Edited by Another JR
  • Like 4
Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
7 hours ago, Another JR said:

The transmission was working fine, and I wasn’t going to lie to them.

 

How refreshing! Well played. 

  • Like 1
marpel Enthusiast

marpel

Posted
Posted

As I read this thread, we just finished a day of towing up and down hills for about 300 miles, with ambient temps up to 93, and tranny down-shifting often to 4th. Tranny never went above 183. ‘22 Sierra 2500HD.

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SoCal Angler Enthusiast

SoCal Angler

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6 minutes ago, marpel said:

As I read this thread, we just finished a day of towing up and down hills for about 300 miles, with ambient temps up to 93, and tranny down-shifting often to 4th. Tranny never went above 183. ‘22 Sierra 2500HD.

You have the 6.6L Gas and 6 speed auto? "70" TBV?

 

If so, I'm very puzzled...how I can get to 185F driving solo, not towing, within 45 miles/one hour of hwy/city flat driving????

Another JR Senior Enthusiast

Another JR

Posted
Posted
19 minutes ago, SoCal Angler said:

You have the 6.6L Gas and 6 speed auto? "70" TBV?

 

If so, I'm very puzzled...how I can get to 185F driving solo, not towing, within 45 miles/one hour of hwy/city flat driving????

His 2022 would have the new valve. The changeover in production was April 2021. 

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