tranny trouble

[AZBUCKEYE]

My 2018 Sierra SLT 4x4 crew cab with 33,000 miles down shifts to first when coasting down long grades, and using cruise. Sometimes when the grade braking is engaged and when it's not engaged! No codes, took it to dealer and they said all was normal. this Is the second time to this dealer. Anyone had a problem like this. Great truck other than this one problem

[Snowcamo]

Find a tuner and get that resolved. It should not be hard to get resolved.

[Black02Silverado]

Is it down shifting to first or to the next lower gear?  Big difference because it will not go to 1st over a certain speed.  It is also supposed to do that when using cruise to help maintain the speed you selected and not go over.

[AZBUCKEYE]

The tach gies over 4,000 , I'm assuming it's first. this is at 50+mph.

[rav3]

20 minutes ago, AZBUCKEYE said:

The tach gies over 4,000 , I'm assuming it's first. this is at 50+mph.

Mine does it too. I think it's normal. BTW, that's not 1st gear.

You can defeat this by pushing in the "tow" button on gear shifter for about 5 sec or so. It will rest at next start up.

You'll also see your pil pressure jump from 40 psi to 60 psi

[AZBUCKEYE]

What do you mean by tuner? The dealer had a transmission man with 20 years service they told me to get rid of k&n filter.

[AZBUCKEYE]

Ok thanks

[rav3]

12 minutes ago, AZBUCKEYE said:

What do you mean by tuner? The dealer had a transmission man with 20 years service they told me to get rid of k&n filter.

I'd get rid of it too. I could never notice any additional power & it'll foul your AF sensor with oil. Noting wrong with OEM filter unless you listen to the sales pitch of K&N. 

[Black02Silverado]

To each their own but I change my air filter out every 15k.  I just go to Walmart or check Amazon for the least expensive one.  My UOA's show no issues in that regard.

[AZBUCKEYE]

Thanks

4 hours ago, rav3 said:

I'd get rid of it too. I could never notice any additional power & it'll foul your AF sensor with oil. Noting wrong with OEM filter unless you listen to the sales pitch of K&N. 

Got one