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Update on 2021 8 speed issues


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Earlier this year I recommend that you should not purchase an 8 speed truck based on my problems.  My dealer finally called GM and asked what to do about the rough downshifts to 1st gear. The head GM transmission tech recommend a new valve body.  A new one was ordered and replaced. It has been over 800 miles since the repair and it is operating perfectly. I am now very happy with the performance of this transmission with the 5.3 V8.

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13 hours ago, Chris Callanan said:

Wonder how hard it would be to get my dealer to do this...  Any TSB?

If you are still in warranty all you can do is ask and push the issue. 

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Good luck pushing the dealer.  My '19 has the same hard shifts, light shudder and slipping as many others do since about 10-12k miles (25k now).  I've been to two dealers complaining.  Both took it out for an "instrumented test drive" and came back telling me it is normal and nothing abnormal was detected on their equipment.  Without any "data" they couldn't justify the warranty claim to do anything else.  One service manager even told me the transmission was "mechanically perfect".  I don't know how she could say that without even dropping the pan.

 

It's as if they think I'm a liar and don't take my concerns seriously.  If it doesn't happen on their watch, it didn't happen.  Mine still has the old fluid and neither dealer will even give me quote so that I can pay them to flush the fluid with the new fluid.  Forget the warranty claim.  I just want to try something and see if it makes any difference.

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My 2015 8A had the occasional hard shift out of first and then shudder around 40k miles and it ended up being the torque converter. Common issue back then. Got a new TC (different part number) and neither problem ever return. Just traded in with 87k miles. There was a whole long TSB on the 8A problems and how to diagnose and fix them. Is that no longer applicable?

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On 10/4/2021 at 9:12 PM, mbaee said:

Good luck pushing the dealer.  My '19 has the same hard shifts, light shudder and slipping as many others do since about 10-12k miles (25k now).  I've been to two dealers complaining.  Both took it out for an "instrumented test drive" and came back telling me it is normal and nothing abnormal was detected on their equipment.  Without any "data" they couldn't justify the warranty claim to do anything else.  One service manager even told me the transmission was "mechanically perfect".  I don't know how she could say that without even dropping the pan.

 

It's as if they think I'm a liar and don't take my concerns seriously.  If it doesn't happen on their watch, it didn't happen.  Mine still has the old fluid and neither dealer will even give me quote so that I can pay them to flush the fluid with the new fluid.  Forget the warranty claim.  I just want to try something and see if it makes any difference.

If they will not give you a quote on changing out the fluid, time to find another dealer.  Even call GM and state that. 

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This is the only reason I got rid of my 2018 Sierra SLT 6.2L with the 8 speed. Truck was awesome out on the highway, got 23-24 mpgs running 70 all day long. BUT in town driving was HORRENDOUS!!  The 1st to 2nd clunking and hesitation drove me nuts. Dealership reflashed it 3 times (didn't help) wouldn't change the fluids in it or anything else. Said it was normal behavior per GM.  Found my 2019 10 speed and haven't looked back. I don't get the MPGs of the 2018 but the shifts are amazing! 

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Every truck I've had over the last several years has had more and more gears in the tranny - 4, 6, 8, 10.  Every time I miss the previous tranny as I like the way they held the gears longer.  I really liked my 8 speed once the initial problems were fixed.  This 10 speed shifts fine, but it feels almost like a CV to me with all the shifting going on.  I think 8 was the sweet spot and 10 might be too many.  Maybe it'll grow on me over time?

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On 10/6/2021 at 4:17 PM, TxTruckMan said:

Every truck I've had over the last several years has had more and more gears in the tranny - 4, 6, 8, 10.  Every time I miss the previous tranny as I like the way they held the gears longer.  I really liked my 8 speed once the initial problems were fixed.  This 10 speed shifts fine, but it feels almost like a CV to me with all the shifting going on.  I think 8 was the sweet spot and 10 might be too many.  Maybe it'll grow on me over time?


Im not sure why that’s a bad thing?

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