Transmission Slip

Cvincent · May 16, 2016

I am just wondering if anyone else has had a similar problem...

This morning, after dropping off my little girl at daycare, I took off from the daycare parking lot not pressing the gas too much since the roads were wet, between 2-3 gears (I think) it felt like it slipped, I could hear the engine rev between gears. A friend of mine said he thinks it is normal because of the new software to try to smooth out shifts?

I should add I have about 4k miles on it and it has happened about 4 times.

I have a 2015 Crew Cab Denali 4WD 1/2 ton with 5.3 and 6 speed tranny.

thanks all

andyhaug · May 16, 2016

Could be 1 of 2 things. There is something with this transmission where it requires an air purge. The first time it shifts from 2-3 it runs a purge cycle which must be opening another solenoid somewhere causing it to not lockup solid in 3rd. It will shift, do the air purge, then the RPM drop again as it finally makes it to 3rd.

It could also be a flare. Mine has had in intermittent issue where if I park and shut the truck off so that I do not need to use reverse to go again, sometimes when restart and go directly to drive it will flare the first time when it shifts from 2-3. When it shifts from 2-3 it disconnects from 2, revs the engine 200 RPM, then puts it in 3rd.

20L8TSierra24 · May 17, 2016

Mine does this. Most of the time in tow/haul mode. I wasn't too concerned because it's only happened about 8 times in 30k

Cvincent · May 17, 2016

Andrew it happened to me just like you said, I backed into the parking space so when I left I just dropped in D and took off. I guess it is nothing to be concerned over then?

andyhaug · May 18, 2016

I wouldn't say that it is nothing to be concerned about. The first time it happened to me I had my foot to the floor, it flared at red line. I explained to the dealer exactly how to reproduce it, but I think only 10% of that got through. They replaced the transmission anyway after the GM field rep looked at it. Transmission #2 started it again at 2000 miles, but is not as reproduce-able. Transmission #1 did this about 90% of the time when it was set up in the sequence to do it, #2 is about 5%. Now I am stuck with it, my dealer is telling me everything is normal, the clunking the flaring and the horribly slow shifting, and they will not even look at my truck anymore. GM is not much help either, they keep telling me to take it back to the dealer. I am going to dealer #3 later this week, but all I can reproduce now it the severely delayed downshift along with it going from 4th to 3rd to 2nd when I request a downshift. Why can't it go from 4th to 2nd?