8 SPEED TRANSMISSION ISSUES

[Siebersh]

LOL ! I have rebuilt all but the last 3, favorite to build was the turbo 350....Harsh down shifts slipping 1-2 shifts are NOT normal the dealer uses the words its common. The only thing common is the complaint they need to fix the issues!

[elcamino]

22 hours ago, Siebersh said:

First of all I don't nitpick! I'm a certified class "A" MECHANIC for over 37 years and specialized in transmission rebuilding

if you think all these issues are normal then that's your opinion, I telling all the others that this is NOT normal for a new vehicle at any price. My truck has 1800 miles on it and a price tag of $60,000 the issues were not present when I test drove the truck and if they were I would never have bought it. This is not my first new GM vehicle but definite the first with all these issues. 

Get used to it, this is the new norm with vehicles.  They are designing for fuel economy and emissions and the computers are driving the vehicle.  Don't think for minute GM is the only one, they all have the issues. I have a friend long time RAM owner since the 80's and he is have all kinds of issues (he says) the dealers can't and won't fix because to them its not a problem but the way its designed. He looking at trading the 18 for a Furd.

Edited June 2, 2021 by elcamino

[It's Tim]

 

On 5/18/2021 at 10:17 AM, Siebersh said:

Hi,

Still looking for some help with my 2020 Silverado my transmission has a 1-2 shift slip this only happens first shift of the day after that good for the rest of the day. 

 

23 hours ago, Siebersh said:

First of all I don't nitpick! I'm a certified class "A" MECHANIC for over 37 years and specialized in transmission rebuilding

[Siebersh]

2 hours ago, It's Tim said:

 

 

How can I order one 

[Agriont]

On 6/1/2021 at 2:44 PM, lebag335 said:

With all that transmission training, you should tear yours apart and report back any findings of fault. Sounds like it wouldn't be anything for you to do this and might help others to boot?

His point is this is a new truck, it should have no issues.  Who would tear a new truck apart?  Good grief.

[Grover2828]

I have this exact issue with my 2021 Silverado. Crew cab. 2.4L engine. Transmission slips from 1st to 2nd gear in the mornings. Taking it into dealership tmrw for inspection. 

Edited February 10, 2022 by Grover2828
typo

[BlancoSilverado]

I have installed the STL010 and found that i started having this slip/clunk on the first ship of the day, i remedy this by shifting to neutral before any gear, wait 2-3 seconds then drive, and then and only then i do not have it happen again, i might put the thermostat back in to see if it makes a difference. 

 

Try this and see it it "fixes" the problem. 

[dgstarr63]

2021 5.3, 8 speed. My dealer finally replaced the valve body and there have been no problems since then.

[175vTrailbossLT]

I read the long threads about this when I got my 2019 new 2 years ago. Decided to forget about it and not sweat it. Warranty for 3 years plus I got the extended 5 year on top of that so f it. 30k mi now. I had 1 really bad experience witht the transmission. Felt like someone crashed into me it jerked so hard. Other than that it for sure does NOT have a smooth transition from P to D. If you are parked with foot on brake and make the witch to D, it definitely 'bounces'. My old 2011 6 speed is smooth as butter and never does that. 

 

[voided3]

20 hours ago, BlancoSilverado said:

I have installed the STL010 and found that i started having this slip/clunk on the first ship of the day, i remedy this by shifting to neutral before any gear, wait 2-3 seconds then drive, and then and only then i do not have it happen again, i might put the thermostat back in to see if it makes a difference. 

 

Try this and see it it "fixes" the problem. 

Our '21 5.3 8-speed truck does the "first shift of the day" 1-2 slip/clunk. For reference, I always let the truck warm up for a minute or two before backing out, and always come to a complete stop when shifting from reverse to drive. Today I tried your trick (leaving it in neutral for three seconds before shifting to drive) and it didn't do the 1-2 slip/clunk. 

[Chris Loesch]

I also have the first shift of the day P-1 clunk / lurch and sometimes the 1-2 slip / clunk with my 2021 Sierra. It's pretty pronounced.  The P-1 clunk/ lurch feels like the vehicle is about to takeoff when you have your foot on the break and put it in gear.  Usually this only happens first thing in the morning.  The 1-2 slip / clunk is more intermittent. My 2017 never did this, EVER.  I did have a 2006 trailblazer that was TERRIBLE with slip / clunks going from 2-3 sometimes other gears and I  thought GM had dealt with this problem years ago, but apparently not.  Wonder if these transmissions are coming from the notorious Tonawanda Transmission plant in Buffalo, NY near where I used to live. 

 

I'm not happy about this either as I know a defective valve body assemblies can damage the rest of your transmission in time.  Is this a design flaw or bad parts based on what ya'll are hearing?  Gonna take mine in next week and drop it off with the dealer.  No way am i gonna put up with this slip clunk nonsense with only 5,000 miles on a brand new $56k truck.   

[xtrythis1]

On 2/11/2022 at 12:55 PM, voided3 said:

Our '21 5.3 8-speed truck does the "first shift of the day" 1-2 slip/clunk. For reference, I always let the truck warm up for a minute or two before backing out, and always come to a complete stop when shifting from reverse to drive. Today I tried your trick (leaving it in neutral for three seconds before shifting to drive) and it didn't do the 1-2 slip/clunk. 

Wow. May try this trick! My 2020 5.3 8 speed does the 1/2 slip bang cold, first shift of the day which is pretty annoying for a 60k$ truck! 

[Grumpy Bear]

On 2/10/2022 at 4:42 PM, BlancoSilverado said:

I have installed the STL010 and found that i started having this slip/clunk on the first ship of the day, i remedy this by shifting to neutral before any gear, wait 2-3 seconds then drive, and then and only then i do not have it happen again, i might put the thermostat back in to see if it makes a difference. 

 

Try this and see it it "fixes" the problem. 

 

The issue is air trapped in the valve body. What you suggest was in a GM memo. It purges the air form the system. Somebody has a 'zip kit' with O rings for the plugs that stops this. Body leaks like a sieve.  SONNAX perhaps. I don't remember. Anyway your procedure will work. One and done.  

[BlancoSilverado]

On 3/12/2022 at 5:24 AM, Grumpy Bear said:

 

The issue is air trapped in the valve body. What you suggest was in a GM memo. It purges the air form the system. Somebody has a 'zip kit' with O rings for the plugs that stops this. Body leaks like a sieve.  SONNAX perhaps. I don't remember. Anyway your procedure will work. One and done.  

Hey Grumpy, 

 

Do you now how hard it would be to swap this out while the trans is in the truck? There is probably a video/ instructions on removing the valve body and two simple pins and swap?

**

You thinking;

https://www.sonnax.com/parts/5461-shift-zip-kit or 

https://www.sonnax.com/parts/5459-tcc-zip-kit

 

I really like that Sonnax has instructions on their website. Only $175-200 per kit, doesn't seem too bad. 

**

Edited March 14, 2022 by BlancoSilverado
** added more info**

[Grumpy Bear]

3 hours ago, BlancoSilverado said:

Hey Grumpy, 

 

Do you now how hard it would be to swap this out while the trans is in the truck? There is probably a video/ instructions on removing the valve body and two simple pins and swap?

**

You thinking;

https://www.sonnax.com/parts/5461-shift-zip-kit or 

https://www.sonnax.com/parts/5459-tcc-zip-kit

 

I really like that Sonnax has instructions on their website. Only $175-200 per kit, doesn't seem too bad. 

**

 

@newdude would be way more knowledgeable on this transmission than I. Just shared what I read on the topic.