8 speed issue

[Crimson6.2L]

So for the past couple of months my 8 speed has had fluctuating rmps when driving at a constant speed and shuddered somewhat. Yesterday on my way home from work it got really bad and now has the vibration that shakes the steering wheel. I know it’s part of the torque converter problem and it’s going Monday to be looked at. They said they will flush it change the filter and use a synthetic fluid this time. I know a few people have had this done and was wondering if it actually fixed it or not. 

[scott.moody.9401]

So for the past couple of months my 8 speed has had fluctuating rmps when driving at a constant speed and shuddered somewhat. Yesterday on my way home from work it got really bad and now has the vibration that shakes the steering wheel. I know it’s part of the torque converter problem and it’s going Monday to be looked at. They said they will flush it change the filter and use a synthetic fluid this time. I know a few people have had this done and was wondering if it actually fixed it or not. 

Mine started doing the exact same thing. I have an appointment in 2 days to take it in.

One other thing I have noticed, is the trans temp reading is erratic. By that I mean it will read 25 deg below ambient when starting out. It will jump 40 to 50 degrees in a second or 2. It fulctuates wildly and does not correlate to reality. It may be related

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[Crimson6.2L]

2 hours ago, scott.moody.9401 said:

Mine started doing the exact same thing. I have an appointment in 2 days to take it in.

One other thing I have noticed, is the trans temp reading is erratic. By that I mean it will read 25 deg below ambient when starting out. It will jump 40 to 50 degrees in a second or 2. It fulctuates wildly and does not correlate to reality. It may be related

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It also seems to not know when to shift and up shifting from 2nd to 3rd will feel like it’s making the truck bounce. Let me know if it works when you get it back. Did they give you a time frame on how long it would take?

[Black02Silverado]

From what I have read on here and on the Camaro forum, doing a full transmission fluid exchange takes care of the problem most of the time.  

[EDL]

Ugh, you guys are scaring me.  I started having the transmission surge at vehicle start up yesterday, but someone posted the TSB that it is normal and no repair required, and today I did like someone suggested and let it idle for about 30 seconds in park before shutting it down.  It never surged at start up once, so the idling thing appears to work.

 

I do have the thunk when coming to a stop as it downshifts from 2nd to 1st.  Today a couple times it thunked hard after coasting then getting back on then throttle at low speed (like coming to a stop light, but not completely stopping and adding a little throttle to move up another 10 feet).   It felt like when you have a really bad u-joint, or like there's a lot of slack or lash in the gear mesh.  Press the pedal and it spins up to take up the slack and then thunk when everything engages.  It only did it a couple times, but that's something else to keep my eye on.

 

God, I hope this thing doesn't turn out to be a headache.  I haven't had a Chevy vehicle since 2001 and I so love everything else about the truck, please, please, please don't become the reason for me to leave Chevy again....amen. :-)

[Crimson6.2L]

It’s crazy how strange it acts when cruising around but at wot it shifts so smooth. No problems at all

[Black02Silverado]

24 minutes ago, EDL said:

Ugh, you guys are scaring me.  I started having the transmission surge at vehicle start up yesterday, but someone posted the TSB that it is normal and no repair required, and today I did like someone suggested and let it idle for about 30 seconds in park before shutting it down.  It never surged at start up once, so the idling thing appears to work.

 

I do have the thunk when coming to a stop as it downshifts from 2nd to 1st.  Today a couple times it thunked hard after coasting then getting back on then throttle at low speed (like coming to a stop light, but not completely stopping and adding a little throttle to move up another 10 feet).   It felt like when you have a really bad u-joint, or like there's a lot of slack or lash in the gear mesh.  Press the pedal and it spins up to take up the slack and then thunk when everything engages.  It only did it a couple times, but that's something else to keep my eye on.

 

God, I hope this thing doesn't turn out to be a headache.  I haven't had a Chevy vehicle since 2001 and I so love everything else about the truck, please, please, please don't become the reason for me to leave Chevy again....amen. :-)

How many miles are on your truck?  If it was me, I would do a fluid exchange. If it is under warranty, take it in and have it done. 

[EDL]

I just rolled over 700 miles on it today.

[mookdoc6]

On 7/3/2018 at 3:06 PM, EDL said:

I just rolled over 700 miles on it today.

700?  Flush it Son!  Demand it and pay for the fluid......When you get it back lay into the pedal some it will take a few thousand miles to stop thunking in the 1-3 down shifts but it will disappear....weird but true!  I am sure mine would have gone away sooner if I hit the pedal harder but too late now.. 

[Scooter Scott]

I've had some issues with my new 2018 Sierra Max tow with the 6.2.  Same things as above..surges when starting, thunks when coming to a stop and the shifting is hard sometimes.  I have just over 700 miles on mine as well.

 

So I should take it into the dealer?

[scott.moody.9401]

So my issue was resolved. The dealer verified it was TCC slip. They performed a trans fluid drain and flush 3 times per bulletin. Then performed a service fast learn. The shudder and rpm jump are gone.

The erratic trans fluid temp reading is a faulty sensor. It is in a harness and they had to order it. It will take up to 2 weeks.

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[scott.moody.9401]

It also seems to not know when to shift and up shifting from 2nd to 3rd will feel like it’s making the truck bounce. Let me know if it works when you get it back. Did they give you a time frame on how long it would take?

Only took a full day

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[Crimson6.2L]

1 hour ago, scott.moody.9401 said:

Only took a full day

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Good deal. I’m leaving town next week and didn’t really want my truck setting at the dealership until I got back 

Edited July 7, 2018 by Crimson6.2L
Wrong reply

[gtbigup01]

My 2017 Sierra had the thunk on downshifts/creeping down the freeway.  13 months later and 32k miles it has gotten significantly better. Software update did nothing,  and I never got it flushed. So GM has no fix for this "#worksasdesigned" but they have collaborated with the Blue Oval to create the 10 speed auto. I recently drove a rented F150 with the 10 speed auto and initial impression are ok. This is the same 10 speed that will be in 2019 GM trucks according to reports.

[J_Mas6.2]

my 15 did this, took it in and they changed the Torque Converter.  Solved the issue