Not totally sold that the trans is shot.

[5strmtrp]

I am not sold that my transmission is in need of replacement. I’ve just hit 124,000 on this truck. The trans. Temps have not gotten above 190 and that was in dead standstill traffic in 90 degree heat.
I’m getting a sluggish throttle response. NO codes, thought throttle body or throttle sensor. Nothing..

What I recently did was drop the trans pan and did the 6 quart change with filter. I found black sludge and used motor oil looking fluid.

I’m thinking of flushing it some more. Pop the upper cooler line and keep refilling until the fluid looks normal

Suggestions???

Also what fluid are you all recommending, synthetic stuff, or just the regular dex6?

 

[Foggy]

Dex VI Synthetic is best ... Sounds like the trans has not been serviced regularly.
I wouldn't think that "sluggish" performance really has anything to do with the
trans itself.. If it shifts up and down thru the gears and you can feel the lockup clutch
engaging in the torque converter, it's prob ok.. The weak point of the 6l80e is the
lock up clutch in the torque converter. when it goes it circulated crap all thru the trans
ruining the trans. Maybe this is what is going on, but it's prob too late if that's the case.

Personally, I'd drop the pan again and post up some pics of whats in the pan
and on the magnet.. If it looks better this time, replace the filter, new fluid and send it !

You may be experiencing a VVT issue or just good old maint/tlc stuff like
plugs, wires, filters, etc... Even poor quality gas.

 

[Bill 1960]

Can you elaborate on why you even began with the thought of transmission failure? I don’t see how sluggish throttle response leads there.

It should be easy to discriminate between an engine vs a transmission issue by manipulating the throttle with the transmission in manual and staying in one gear.

 

[5strmtrp]

Dex VI Synthetic is best ... Sounds like the trans has not been serviced regularly.
I wouldn't think that "sluggish" performance really has anything to do with the
trans itself.. If it shifts up and down thru the gears and you can feel the lockup clutch
engaging in the torque converter, it's prob ok.. The weak point of the 6l80e is the
lock up clutch in the torque converter. when it goes it circulated crap all thru the trans
ruining the trans. Maybe this is what is going on, but it's prob too late if that's the case.

Personally, I'd drop the pan again and post up some pics of whats in the pan
and on the magnet.. If it looks better this time, replace the filter, new fluid and send it !

You may be experiencing a VVT issue or just good old maint/tlc stuff like
plugs, wires, filters, etc... Even poor quality gas.

I have done all the basic maintenance items you mentioned here within the last 20,000 miles. The VVT, can you elaborate on it a bit more. I personally hate the AFM setup, drives me nuts at surface street speeds, however that’s when it’s supposed to be efficient. I’ve been using Exxon/Mobil gas midgrade as it seems to work better for some reason with the AFM. It’s more than likely me but.

 

[5strmtrp]

Can you elaborate on why you even began with the thought of transmission failure? I don’t see how sluggish throttle response leads there.

It should be easy to discriminate between an engine vs a transmission issue by manipulating the throttle with the transmission in manual and staying in one gear.

So there are no codes popping up. I’ve been told if there is no codes then to assume all is good. I 1st thought it could throttle body or the accelerator. While at highway speeds it seems that I get a “dead zone” in the pedal. Throttle response at the onset of the pedal, 1/4-3/4 way down there is nothing, mash the pedal and it responds. This happens about 60% of the time. Other times it drives perfectly.

I knew that it was time to change out the trans fluid, last time I did it was about 25000 miles ago. When I dropped the pan and saw how dark the fluid was I started to think the reason for the sluggishness would be that the trans is slipping.

I will run it thru the gears manually and see what it does in the next day or so.

 

[wsteele]

So there are no codes popping up. I’ve been told if there is no codes then to assume all is good. I 1st thought it could throttle body or the accelerator. While at highway speeds it seems that I get a “dead zone” in the pedal. Throttle response at the onset of the pedal, 1/4-3/4 way down there is nothing, mash the pedal and it responds. This happens about 60% of the time. Other times it drives perfectly.

I knew that it was time to change out the trans fluid, last time I did it was about 25000 miles ago. When I dropped the pan and saw how dark the fluid was I started to think the reason for the sluggishness would be that the trans is slipping.

I will run it thru the gears manually and see what it does in the next day or so.

If you changed the transmission fluid 25K ago and this time you had black sludge in the pan, something isn't OK.

 

[Geotrash]

This is a time when the Tech 2 scanner would be a godsend. You could potentially look at the functioning of the accelerator pedal with it, I believe, but @swathdiver would know for sure. Without good data and insight into how your systems are operating, you're left with the parts cannon approach. And in this case, I would be suspecting the accelerator pedal assembly. Rock Auto has the OEM part for $75, which is cheap as far as cannonballs go.

 

[Foggy]

There is an updated accelerator pedal assembly avail from GM...
Your Throttle Body could be gummed up...
If you drive it manual LOW and put it in "4" , Im told that the AFM will not kick on.

As far as the VVT, it runs off oil pressure and gives the camshaft advance/retard
You should be able to see if its being commanded with a good scan tool.
And you can compare your TPS values to Peal Position values to see if that's off too

 

[McLeod Crouch]

I had something similar but my throttle body was pretty dirty. When you clean it just be careful of moving the butterfly flap back and forth, and you will have to plug a scanner in it to relearn the throttle body or it will just idle high. I have seen some people start it let it idle for some time and then turn it off, repeat until normal, or unplugging and plugging it back in.

 

[exp500]

Don't go farther than tow truck range! Now it is a matter of when not if.

 

[5strmtrp]

I went and changed out the fluid 3 times last week. Borrowed a manual transfer pump from a friend of mine. Pumped out the fluid thru the dipstick tube.

Each time I did it the fluid got cleaner. It’s how the color it’s supposed to be. Going to drive it a week and keep checking the condition of the fluid. If it stays normal I’ll drop the pan again and replace the new filter with another one for added insurance.

If not then I have an appointment at the end of the month at my local shop to replace the trans with a GM rebuilt one.

 

[5strmtrp]

I went and changed out the fluid 3 times last week. Borrowed a manual transfer pump from a friend of mine. Pumped out the fluid thru the dipstick tube.

Each time I did it the fluid got cleaner. It’s how the color it’s supposed to be. Going to drive it a week and keep checking the condition of the fluid. If it stays normal I’ll drop the pan again and replace the new filter with another one for added insurance.

If not then I have an appointment at the end of the month at my local shop to replace the trans with a GM rebuilt one.

After nearly 500 miles of driving, the fluid looks normal and it’s shifting perfectly fine. Hopefully I dodged a bullet here, will keep monitoring the color of the fluid in the coming weeks and go from there.
Appreciate all the help you all have posted.

 

[Doubeleive]

some other things to consider if the issue returns or if you just want to do some preventative maintenance, some previously mentioned but MAF could be a culprit (about $70), clean the throttle body, run a couple bottles of injector cleaner thru it for the next few tanks fulls, new air filter, plugs-n-wires were due at 100k, all 4 02 sensors are due at 100k also.
beyond that you could have a injector service done, some places have a machine or tool that connects directly to the fuel rail and they run it thru that way, generally runs about $80 for that service.

 

[5strmtrp]

some other things to consider if the issue returns or if you just want to do some preventative maintenance, some previously mentioned but MAF could be a culprit (about $70), clean the throttle body, run a couple bottles of injector cleaner thru it for the next few tanks fulls, new air filter, plugs-n-wires were due at 100k, all 4 02 sensors are due at 100k also.
beyond that you could have a injector service done, some places have a machine or tool that connects directly to the fuel rail and they run it thru that way, generally runs about $80 for that service.

I went thru my receipts and things I’ve done to the truck. All of this was done in the past 20k or so miles. Last year I had the intake cleaned by the mechanic I use. He mentioned that these trucks are known for them getting gummed up. I will clean the throttle body again, and the plugs wires were all done around this time as well. The weird thing is these truck only have an in tank fuel filter. My 03 Silverado had 2 in tank and along the frame near the middle of the truck. That was originally my 1st idea where to check and replace.

 

[avalonandl]

There is an updated accelerator pedal assembly avail from GM...
Your Throttle Body could be gummed up...
If you drive it manual LOW and put it in "4" , Im told that the AFM will not kick on.

As far as the VVT, it runs off oil pressure and gives the camshaft advance/retard
You should be able to see if its being commanded with a good scan tool.
And you can compare your TPS values to Peal Position values to see if that's off too

AFM can kick on anytime that certain parameters are met.

 

[Swaggerwagon]

Can’t tell you with 100% certainty what the issue is, it I can tell you it’s NOT the gas pedal. Any pedal issue, even for a millisecond, will make the engine drop to idle speed, until you shut the truck off. And you get an immediate ‘check engine’ light. Since we’re spitballing here, it’s been my experience that a clogged fuel filter will stumble every single time you mash the pedal, not sometimes. And once it stumbles a couple times, check engine light pops on, and you’ll pull codes ‘bank 1 lean’ & ‘bank 2 lean’.

Doyoubelieve has the right idea. A lazy MAF sensor will make any truck a dog.

I understand your concern regarding dirty trans fluid, but I think that’s unrelated to your driveability issue