funnyman06

Sounds like the torque converter is unlocking before the shift to 4th. So 3rd TC locked, 3rd unlocked, 4th locked.

scottmoyer

Airplane_guy mentioned exactly what I'm experiencing. While driving through town at 25-45mph, maintaining whatever speed I'm cruising, the trans will shudder/buck/chug if I even slightly touch the throttle. I too have a 5.0L with 3.55 gears. I have about 1600 miles on my truck and it hasn't gotten any better. I took it in last week and the dealer had my truck for two days and never looked at it, so I took it back and will schedule with another dealer. Now the question comes down to if the last service appointment will be counted as a service repair, if they never fixed anything.

Yesterday, there was an accident that backed up traffic. I was driving slow but it was constant accelerate, then stop. The trans was bucking so bad for the 1 hour commute, I wanted to drive the truck off a cliff!!! It appears the trans learns bad habits faster than good, because my commute today was horrible at all speeds with chugging and shuddering even at 60mph.

GreenandGold831

iTrader: (1)

2AF150GA

Update on my 2018 2.7L: The 3rd to 4th gear hesitation shift has disappeared now. Not sure if it's due to it being warmer out (mornings in the 70's and evenings in the 80-90's) or if it's just got more miles on it (almost 3000 now) and everything has just smoothed out. Transmission shifts nice and isn't jerky or anything anymore. Honestly it feels like the whole truck is breaking in/settling in and smoothing out now.

EcoBeast2.7L

I wish this is what happened to me, just passed 10k in my 18 2.7 and still having the exact same issue.

My dad just bought a 18 5.0 lariat and he has the shuttering issues others are reporting with 12k miles.

w00t692

the shuddering i thought was a tsb for misfires or something? maybe look into that.

scottmoyer

I don't know if it was this thread or another, but someone mentioned that the RPM should not be allowed to go down below 1400 and that should solve the problem. Well, I'm here to say that my truck is bucking/stuttering/chugging even at 2k RPM. I tried driving in sport mode while in traffic today and it's even worse. I'm beginning to HATE this truck and wishing I bought the GMC. For the same $52k MSRP, I would've gotten leather, navigation, hd radio, puddle lamps, auto tilt/folding mirrors and Homelink.

I'm hopeful that the dealer I take it to tomorrow can reflash the trans and solve this issue for good!

Mason1198

What engine do you have, and what octane fuel are you using? My 3.5 stumbles and shudders a bit, but mostly at very low RPM's when it's hot and the AC is on. I have found that running 93 octane fuel really helps these 2nd gen 3.5 engines (and for me fixes the shuddering). For me it has a more dramatic effect than it did on my 1st gen 3.5. Perhaps they're pushing the limits of 87 too far. Granted, shouldn't have to run 93 to get a smooth running engine.

scottmoyer

I have the 5.0 with 3.55 gears.

GP-SE

Try a tank of 91 or 94 High Octane fuel and see if it makes any changes, it could be spark knock/detonation. The 5.0 isn't bad for spark knock/lugging, however the 3.5's suffer from it because they like to lug at low RPM/high load. (Cylinder Pressures at their highest)