Transmission problem?

[Blue-14-Silverado]

New to the forum and recently purchased a 2014 Silverado with the 5.3L and don’t know if this is a problem. Live in the Denver area and was driving through the mountains the other day and when I was driving down the mountains the engine would shoot up to around 4500 RPM. Did this about 4 times and only did this when I was going downhill. When it did that I would put it in neutral and pull off the side. Let it sit for about a minute and drive off. Engine temp was around 190 since it was cold outside and the tranny temp was fluctuating between 194-201. Again, It only did this when driving at a downgrade. 

[L86 All Terrain]

Hmmm, I was going to say active grade braking? But 4500rpm is extremely high. Did it throw a check engine light? My 2014 5.3L would slam it self into second or 3rd gear when coasting into town and throw a check engine light, it was a shift solenoid that sticks open so you need a scantool to get it out of that gear. They replaced the TEHCM in the trans but it still did it. I figured it out to be caused by the AFM system and since disabling that system I didn't ever have it do it again. Not saying that's what your problem is, need to know if it had a check engine light. 

[Blue-14-Silverado]

No check engine light came on when it did this. Don’t have any mods to it other than the AFM module.

[JacobC1983]

That is active grade braking.  It is supposed to do that to hold itself back and minimize use of the brakes.

[swathdiver]

4500 isn't anything for an LS motor.  Read your owner's manual.

[Blue-14-Silverado]

I know all about LS motors. I had a 2000 T/A that I did cam, heads, LS6 intake and 6 speed swap to. Just didn’t know if this was normal for the newer LS based engines or for trucks. 

[300 Blackout]

Normal