Stumble/Hesitation AND stalling continuation thread

[jeremiahm]

I just replaced my fuel pump last month as well with not affect on this.

 

[bdbull]

I have always the hard stumble at stops and as part of trying to figure out this issue I put a bottle of LubeGard Transmission Protectant (10oz bottle) based on other posts. Made a huge difference. Seems part of the stumble is low RPM, but the bigger potential issue is torque converter shutter which the LubeGard helps. I saw a huge difference, stops are pretty easy now, still a bit of shutter/stumble, but not much.

My 2 cents, and doesn't count as "strenuous activity". Hope it helps.

So you put the entire 10oz. bottle in? I was thinking of doing an ATF fluid exchange on my truck anyway, so I may throw this in with it.

 

[Foggy]

So you put the entire 10oz. bottle in? I was thinking of doing an ATF fluid exchange on my truck anyway, so I may throw this in with it.

Yes.. The whole bottle of Red LubeGard or the Silver/Plat bottle...
IMO a fluid "exchange" is worthless and can cause more harm than good - unless
you drop the pan and change the filter FIRST.. Clean pan, pan magnet and everything you can
get to.. FIRST or Only

 

[bdbull]

IMO a fluid "exchange" is worthless and can cause more harm than good - unless
you drop the pan and change the filter FIRST.. Clean pan, pan magnet and everything you can
get to.. FIRST or Only

I dropped the pan and did all that about 15k miles ago. I may skip the exchange and just throw the LubeGuard in and see what happens.

I've actually just noticed some transmission issues lately. When cruising at about 40 in sixth gear, it seems like it can't figure out if it should downshift or not. I've never cared for this six speed compared to the four speed I had in my '03 Avalanche. It just never felt right.

 

[Charlie207]

I dropped the pan and did all that about 15k miles ago. I may skip the exchange and just throw the LubeGuard in and see what happens.

I've actually just noticed some transmission issues lately. When cruising at about 40 in sixth gear, it seems like it can't figure out if it should downshift or not. I've never cared for this six speed compared to the four speed I had in my '03 Avalanche. It just never felt right.

Are you still running with the AFM active? When you're cruising in 6th gear @ 40mph it may be in V4 mode, and when you try to give it some throttle the ECU is fumbling with whether it should downshift while still using four cylinders, or activating all eight cylinders to provide adequate cruising power.

I saw a "hack" a when I first got my Yukon where you can run the truck in Manual Mode - Gear 5, and it would disable the AFM. Try that and see if you stay in V8 mode. I've since gotten a BlackBear tune and had the AFM electronically deleted.

 

[bdbull]

Are you still running with the AFM active? When you're cruising in 6th gear @ 40mph it may be in V4 mode, and when you try to give it some throttle the ECU is fumbling with whether it should downshift while still using four cylinders, or activating all eight cylinders to provide adequate cruising power.

I saw a "hack" a when I first got my Yukon where you can run the truck in Manual Mode - Gear 5, and it would disable the AFM. Try that and see if you stay in V8 mode. I've since gotten a BlackBear tune and had the AFM electronically deleted.

I saw someone else mention this a few days ago so I've been driving with the DIC on that display to see if/when it goes to V4. Honestly, it very rarely ever does it. I've noticed it a few times when coasting downhill, but that's about it.

For the hack, do you mean put it in Manual - Gear 5 and leave it there while driving around? Or do you mean put it in Manual - Gear 5 ONLY when I'm up at cruising speed to keep it from going to 6th? I really only do city driving so I rarely get up over 60MPH so not sure how much the AFM kicks in for me.

 

[Charlie207]

I saw someone else mention this a few days ago so I've been driving with the DIC on that display to see if/when it goes to V4. Honestly, it very rarely ever does it. I've noticed it a few times when coasting downhill, but that's about it.

For the hack, do you mean put it in Manual - Gear 5 and leave it there while driving around? Or do you mean put it in Manual - Gear 5 ONLY when I'm up at cruising speed to keep it from going to 6th? I really only do city driving so I rarely get up over 60MPH so not sure how much the AFM kicks in for me.

Start your car, put it in Manual mode, select Gear 5, and leave it there.

Cycle through your dash info display, and observe INSTANT MPG, and it'll show drive mode: V4 or V8.

There are several YouTube videos showing it in effect.

 

[Charlie207]

Let us know how it works for you.

I've mentioned this procedure three or four times over the last six months, and no one ever reports back.

 

[bdbull]

Let us know how it works for you.

I've mentioned this procedure three or four times over the last six months, and no one ever reports back.

I'll give this a shot when I head out this afternoon. Although I'm pretty sure it's the transmission now. I've been watching the DIC the last couple of days and it very rarely goes into V4 mode. In fact, I made a trip all the way across town and back, about 30 miles, and I never saw it hit V4 once.

I did put the bottle of LubeGuard in last night so we'll see if that has any effect on it. I just put a transmission in my wife's '15 Tahoe so it's only fitting that mine would start to go out now as well. As my dad used to say to me when I was young, "I'll just go out back and pick some more money off the money tree."

 

[Mad-Max]

We are having this exact issue with a 2013 Yukon XL Denali (6.2) we're looking at - currently have it on a 24hr test drive. I'm very interested in any follow-up thoughts about the root cause.
- Sam