Speedo correction w/ gear swap + trans temps

[EngiDent]

Hey guys
2010 Avalanche LTZ, 4x4, factory tow package, P3 brake controller, otherwise stock. 3.42 gears, but does have factory trans cooler. I tow a ~5500lb 1967 Airstream with it. My question is, if I go from 3.42 to 4.10, no change in stock tire size, what is involved in correcting the speedo /odo? Does a module have to be flashed or something, or change something with speed sensor? Also, what would you call normal trans temps while towing? I'm running about 190 on flat highways while towing, but closer to 200-205 in slightly hilly (not mountain) areas or in bumper to bumper traffic in mild (85 degree) heat. Would trans temps necessarily come down with gear swaps (front and rear of course), or should I be looking into an upgraded cooler? Thanks

 

[MS03 2500]

210 220 degrees is ok on hills, I would not try 4.10s with the 6 speed tranny. Now the factory transmission cooler is rather small so that is the only thing I would look at. You might want to look into some load c or d rated tires

 

[EngiDent]

Good info, thanks. I'm running Falken Wildpeak H/T tires, 117H rating, stock size. Good value, tough tires, not as smooth as equivalent rated Michelins but couldn't find Michelins for this size wheel rated how I wanted them.

 

[MS03 2500]

Your tranny will display it's hot at 266 F, so keep it far from that.

 

[BainMan]

These transmissions want to be heated up to a certain level and intentionally warms the transmission fluid via the radiator. I've found it maintains about 90 degrees above whatever the ambient temperature is, 10-15 more if you are towing sounds reasonable to me. I had your same concern and considered a transmission cooler but from what I read at the time 200 degrees is a good temperature when in summer weather of 90+.

You may not change the axles now but just some extra info, the speedometer can be corrected for tire/axle change with handheld tuner/programmers. Here is an example video