Towing and safe transmission temperature?

[ToddEdge]

I tow a 6800# boat during the summer months with my '07 Denali. I burned up a transmission towing this same boat with a Hummer H2 last summer, although it had 37" tires, weighed more, and had the 6.0 motor. I'm not going to risk burning up another transmission. I'm curious what others transmission temperatures are when you tow? I drag the boat 90 miles to and from the lake. From what I've read, as long as I keep it under 230 degrees, it seems as if it is not doing any damage. We drove to the lake last week without the boat and the transmission was between 158 and 170 degrees the entire ride.

Thanks,
Todd

 

[yates ™]

I would get nervous before 230

Buy an external transmission cooler and that will help.

 

[ToddEdge]

I thought all the Denali's had an external transmission cooler factory mounted in front of the radiator?

 

[yates ™]

No idea.

 

[scottg918514]

I thought all the Denali's had an external transmission cooler factory mounted in front of the radiator?

It should, mine does. Just look for the small radiator looking thing in front of the real radiator. My tranny got up to 189 yesterday . Towing boat to lake next week, will keep an eye on it.

 

[ScottyBoy]

I would pull over if my trans temp went over 200°
Mine never gets over 180-190 in the triple digit Louisiana summers.
On a mild day it stays about 160°

 

[imi4tth3w]

trans temps should be very similar to engine temps. if it goes over 210-220 i'd be a little cautious. based on what your temps are so far, i wouldnt' worry about it.

 

[TowGMC]

Pulling my 6800 lb race car trailer I'll see 210-220 trans temps if I leave it in D. So I pull it into Manual mode and leave it in 5th to reduce the trans hunting between gears. And on long grades I'll put it in 4th for the same reason. If I hold a lower gear the trans temps rarely get above 200, which is perfectly fine for a good quality oil. It's the constant shifting when leaving the drans in D with a lot of weight behind that causes all the friction which means heat.

Oh, and I keep it in Tow mode all the time I'm towing. Per a GMC engineer I spoke with, the Tow/Haul mode changes the shock valving in the electronic shocks and it opens the trans cooler thermostat at a lower temp too. Can't validate the trans tstat but I do know the shocks are firmer this way. And an added benefit is that the lane change feature on the blinkers changes from an automatic 3 blinks to 6 blinks, much more appropriate when changing lanes with an extra 28' of length behind me.

 

[ToddEdge]

I towed our boat home from the lake yesterday and very pleased with the Denali. My H2 struggled the entire way and I was always on the edge of overheating. The Denali towed great. I rarely ever dropped below 5th gear, even in the huge hills of Tennessee. It got up to 190 while driving under 45 on the curvy lake roads but, on the interstate, it stayed between 170 and 176, which I thought was excellent.

These Denali's are amazing tow vehicles!

Todd

 

[scottg918514]

It should, mine does. Just look for the small radiator looking thing in front of the real radiator. My tranny got up to 189 yesterday . Towing boat to lake next week, will keep an eye on it.

Ok, towed boat to lake today. Boat + trailer = 4.5k #s. Temp in morning was 80, 87-89 coming home. The drive is mostly 55-60 mph rolling county roads. Highest tranny temp reaching, on the way home, was 192.