New truck hot transmission

Evansdad · May 31, 2020

Help,

took delivery of a 2020 2500hd double cab today and driving home the transmission overheated. It is the gas engine. Temp went to at least 277 on the gauge and it told me to pull over and idle. I had it towed to nearest dealer through road side assistance. It had a total of 150 miles on it.

Can the Trans fluid be too low or too full?

what else could have caused this? How much damage do you think would have already been done?

thanks and waiting patiently for Monday morning to call the service dept where it was towed.

CamGTP · May 31, 2020

Yes the fluid could be too full or too low. I take it didn't open the hood and pull the dipstick to check that.

The temp sensor is inside the pan and I've seen them go bad before so there is always that possibility that a sensor just failed. Unless something internally failed there is likely no real damage on a brand new transmission that got hot once. The fluid is brand new and is at it's peak for performance and protection on keeping stuff lubed.

sdelam · June 1, 2020

On 5/30/2020 at 11:39 PM, CamGTP said:

Yes the fluid could be too full or too low. I take it didn't open the hood and pull the dipstick to check that.

The temp sensor is inside the pan and I've seen them go bad before so there is always that possibility that a sensor just failed. Unless something internally failed there is likely no real damage on a brand new transmission that got hot once. The fluid is brand new and is at it's peak for performance and protection on keeping stuff lubed.

There is no Trans dip stick on 2020 models

newdude · June 1, 2020

I wonder if the thermostat for the trans lines is stuck closed.

CamGTP · June 1, 2020

Both gas and diesel no longer have dipsticks?

Evansdad · June 4, 2020

So dealer took it for two trips and transmission temp were as follows:

20 min - 216 degrees

45 min up steep mountain - 233 degrees

my trip 1/2 way home was 1.5 hours - went to 277 degrees. He said everything mechanical was fine and no codes were detected. Plan on going to get it Saturday morning. What trans temp does everyone’s 6.6 gas seem to operate at? My 2011 6.0 never goes over 200.

Thanks in advance.

jjackkrash · June 17, 2020

I've never had one of my DMax trucks ('13, '16, '19, '20) climb over 190 under any condition, including towing heavy over passes in 100 degree weather. They usually run under under 160. I don't know about the gassers, but that still seems really hot.

Evansdad · June 17, 2020

Update: Dealer still has it, waiting on a transmission cooler bypass valve. They had to order the part. Keeping the miles low if nothing else. How willing would Gm be swayed to offer an extended warranty or extended onstar subscription since I have had the truck for 3 weeks and only could drive it 3 times? Each time to a dealership for tranny issues.

SkidooSteve12 · June 17, 2020

On 6/3/2020 at 9:59 PM, Evansdad said:

So dealer took it for two trips and transmission temp were as follows:

20 min - 216 degrees

45 min up steep mountain - 233 degrees

my trip 1/2 way home was 1.5 hours - went to 277 degrees. He said everything mechanical was fine and no codes were detected. Plan on going to get it Saturday morning. What trans temp does everyone’s 6.6 gas seem to operate at? My 2011 6.0 never goes over 200.

Thanks in advance.

My 2020 6.6L Gasser was up to 180 when I was keeping track of it for this other thread.

And I'd definitely ask the dealer about an extended warranty or extended OnStar plan at least for your troubles. Or they might cut you a big discount on some truck accessories.