Shifting problems-Just had AFM delete.

Pierce Vaughn · April 16, 2020

Howdy all,

I’ve just had my 5.3 engine rebuilt on my 2014 Silverado due to lifter problems. This truck has the 6 speed transmission.

Trucks’ problem:

Very often, when I’m accelerating or cruising at lower-mid rpms I get a weird hesitation/uneven lack of power that doesn’t go away unless I give it more pedal, or let off.

It usually happens when I’m on a straight way, maintaining speed, and want to pick up just a little bit of speed. Or If I’m cruising up a hill it acts up until it down shifts.

What it does could be described as a “miss” or miss fire, but it feels more like the truck just isn’t shifting soon enough. Kinda like riding an atv/dirt bike riding in too high a gear putting more load on the engine.

Also, tow/haul mode makes it pretty much unnoticeable, but I can kinda tell it’s still there.

I’m not really sure if it did this before my rebuild. I didn’t have the truck long before then.

- Could this be something with the computer ?it was sent off to have the v4 mode complete programmed out of it, but, I’m wondering if the transmission still has parameters for v4 mode that kick in.. just a thought. I’m really not sure on this one.

Anyone experiencing this sort of thing?

I could be completely wrong about it not shifting soon enough but that’s just the feeling.

Thanks for any input/advice on what this is and fixing it.

-Pierce

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Pierce Vaughn · April 16, 2020

Also, forgot to mention: my rpms will just go up and down ~100 rpms usually when it’s acting up. I can put a video of that if that would help diagnose.

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CamGTP · April 16, 2020

There is nothing else to change for the AFM on the transmission side of the calibration. It's a master enable/disable table that gets change on the PCM half of the calibration, once changed that is all that needs to be done.

The 100rpm up or down sounds like it's trying to decide if it needs to keep the torque converter locked or unlocked. Things like that could be changed with the tune if someone knew what they were doing with a computer. There are many shift settings and torque converter settings that someone can do.

Though it is entirely possible that even with a tune that the torque converter still has an internal problem.

Pierce Vaughn · April 16, 2020

There is nothing else to change for the AFM on the transmission side of the calibration. It's a master enable/disable table that gets change on the PCM half of the calibration, once changed that is all that needs to be done.

The 100rpm up or down sounds like it's trying to decide if it needs to keep the torque converter locked or unlocked. Things like that could be changed with the tune if someone knew what they were doing with a computer. There are many shift settings and torque converter settings that someone can do.

Though it is entirely possible that even with a tune that the torque converter still has an internal problem.

Thanks for the reply.

If it was the torque converter, I’m wondering if I should be able to just replace it and fluids and resolve it. I was thinking about having someone look at tuning it but I wouldn’t want that to “fix it” if I actually did have a internal problem with it.

Anyone know if I would have any codes readable from the transmission ? I’m not sure if that’s possible with a regular obd2 reader.

When I had my engine done my transmission fluid was a little bit low.

Thanks.

-Pierce

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Ozer · April 17, 2020

You may be having the very common TQ slipping issue. Its a sign that its on its way out. I had my trans fully rebuilt at 122k miles.

If you catch it early,before any of the clutches get damaged you may be able to just get the TQ replaced but with a fresh rebuilt, i would say a rebuild trans will be ideal for longevity.

Pierce Vaughn · April 18, 2020

You may be having the very common TQ slipping issue. Its a sign that its on its way out. I had my trans fully rebuilt at 122k miles.
If you catch it early,before any of the clutches get damaged you may be able to just get the TQ replaced but with a fresh rebuilt, i would say a rebuild trans will be ideal for longevity.

Hmm. Well I’m hitting 150k on mine. I’d replace the torque converter,but like you say ideally I’d do the trans and torque converter if I’m just going to go that route. And I just had my engine done last month *sighhh*

About how much did you have your transmission done for on your truck if you don’t mind? And if it’s a similar year as mine is.

Maybe after all this I’ll have a pretty stout truck for a while.
Thanks for the help.

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Ozer · April 18, 2020

Hmm. Well I’m hitting 150k on mine. I’d replace the torque converter,but like you say ideally I’d do the trans and torque converter if I’m just going to go that route. And I just had my engine done last month *sighhh*

About how much did you have your transmission done for on your truck if you don’t mind? And if it’s a similar year as mine is.

Maybe after all this I’ll have a pretty stout truck for a while.
Thanks for the help.

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Mine was 2700 from a local shop. Dealer wanted 5300 to put in another GM one. I got mine built with better parts and added shift lit and thermostat delete and few other "better than GM" replacement parts.

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Pierce Vaughn · April 18, 2020

Mine was 2700 from a local shop. Dealer wanted 5300 to put in another GM one. I got mine built with better parts and added shift lit and thermostat delete and few other "better than GM" replacement parts.

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Okay cool. Well, maybe I’ll drive it like it is for a little bit unless it gives me a lot of trouble and then just have the transmission done later. what is the other thing you are talking about with the shifting part(s)?

I wonder if a fluid change would smooth things out for now?

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Ozer · April 18, 2020

Okay cool. Well, maybe I’ll drive it like it is for a little bit unless it gives me a lot of trouble and then just have the transmission done later. what is the other thing you are talking about with the shifting part(s)?

I wonder if a fluid change would smooth things out for now?

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GM does have a new fluid out that's supposed to be better so you may want to get that and do a pan drop and change. Then you can see if the transmission pan magnet has any metal on it.

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CamGTP · April 18, 2020

The GM fluid is for the 8 speeds.

The 6 speed should only use Dexron 6 fluid only.

lryfer · May 2, 2020

Just picked up my CPO 2018 with 6 speed and 5,600 miles on it. Sounds like mine doing the same thing. Feels like hesitation or something holding it back from running smooth down the road. My 2006 is smooth as silk. Reading this post i am wondering if my newly acquired truck has an issue. Very noticeable to me no light lit on dash or anything.

Is it possible just not pushing on gas pedal hard enough?

This something to be concerned about tearing up the tranny? My truck still under warranty so would want to address this while warranty status.

What is the AFM Automatic Fuel Management? a guess.

JimCost2014 · May 2, 2020

18 hours ago, lryfer said:

What is the AFM Automatic Fuel Management? a guess.

The AFM system, or Active Fuel Management system, is used to limit the power of a GM 6-cylinder or 8-cylinder engine and help increase its fuel economy. The system itself is activated when the engine reaches certain perimeters, such as a cruising highway speed.

In your case the engine will reduce down to 4 cylinders when all conditions are right.

If you look at your DIC while driving, you will see a green V4 or a blue V8 in the bottom right hand corner.

As far as the gas pedal, yes, there is a known flex problem where you need to "stand on it" at times to get the truck moving.

Edited May 2, 2020 by JimCost2014

Pierce Vaughn · May 2, 2020

Just picked up my CPO 2018 with 6 speed and 5,600 miles on it. Sounds like mine doing the same thing. Feels like hesitation or something holding it back from running smooth down the road. My 2006 is smooth as silk. Reading this post i am wondering if my newly acquired truck has an issue. Very noticeable to me no light lit on dash or anything.

Is it possible just not pushing on gas pedal hard enough?

This something to be concerned about tearing up the tranny? My truck still under warranty so would want to address this while warranty status.

What is the AFM Automatic Fuel Management? a guess.

That’s terrible to be happening on such newer trucks. I drive a 2013 Silverado for work and I’ve never felt a problem like mine is having. So I definitely wouldn’t call it normal. I’m still trying to figure out what is going on. I may try some fluid additive and see if that changes anything so I can at least narrow it down.
With yours still being under warranty, you should definitely get the dealer to replace anything to get it fixed. Even if it means having them replace the transmission.

I really hate to but if I can’t get it figured out I’m going to plan on replacing mine in the next year or so.

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cnd4ua · March 11, 2022

Did you get it worked out? I’m having the same problems. Went through lifters, had the delete. But also had a new torque converter and rebuilt tranny and still having these problems. No code, 2 shops and gmc dealership cannot figure it out either.