GTX 980 Ti Hybrid vs 1080 Ti Hybrid Temperatures

[GatorTPK]

I'm been mining with both a GTX 980 Ti and 1080 Ti.  Both cards are Hybrid (water cooled).   The 980 Ti usually reports a max temperatures of 72 C (at 230 watts), while the 1080 Ti reports only 51 C max (at 251 watts).  I thought 72 C was decent until I got my 1080 Ti last week and it's literally 21 C cooler!  The power input and size of radiator should be the only factors in determining the temperature (16nm vs 28nm process generally only matters when figuring efficiency).  Both cards have identical radiators and fans.  Is there something wrong with the 980 Ti's cooling ability?  Again, I only noticed when the new 1080 Ti was a bit cooler.  As far as I can remember, the 980 Ti has hovered around 70 C when maxed out Folding two years ago, (no change over time).

 

If my 980 Ti should be around 50 C like the 1080 Ti, then what are my solutions?  I've redone thermal paste on dozens of CPUs, but never a GPU.  Is it fairly easy to disassemble the video card to put fresh thermal paste on?  

 

Also, how much does ambient air temperature affect the GPU temperature?  If the ambient air is 20 C more, would the GPU be 20 C more?  I tend to think its not that linear.  (The 980 Ti gets air from inside the case, though it's open on both sides now, and the 1080 Ti gets air from the outside front of the case.  The air doesn't seem that much warmer in front of the 980 Ti's radiator since it's completely exposed to outside air 1" away.)  The screen shot shows slightly lower figures than usual.

[Majestic_Koala]

Here is a video on how to do it:

 

[GatorTPK]

Just now, Majestic_Koala said:

Here is a video on how to do it:

 

Thanks for the near instantaneous reply!  So, does it seem likely that the factory thermal paste is deficient?

[Ryzza5]

Is there any perceivable difference in sound/noise level between the two?

[GatorTPK]

9 hours ago, Ryzza5 said:

Is there any perceivable difference in sound/noise level between the two?

When I hold a microphone to the radiator fans, they sound about the same loudness but the 1080 Ti's fan has a lower frequency.  Both fans are the stock fans that came with the Hybrid cards for the radiators and appear identical, certainly the same 120mm size.   The 1080 Ti's fan on the card itself isn't running, never has.  The 980 Ti's fan is running at 1410 RPM.  These fans on the cards are just for cooling of memory and controller (I assume) since the GPUs are water cooled.