Poll: How has your 8-speed been for you?

dkjbama · February 1, 2019

Of course we hear lot of complaints on the 8L90 transmission shuddering and banging. I'm just wondering how many out there have been problem free, since folks with problems seem to be the most vocal (rightfully so). My 9 month old 2018 5.3 SLT PP with 14,000 miles has been flawless except a little thud going from Reverse to Drive when the truck had less than 1,000 miles. How's yours?

Edited February 1, 2019 by dkjbama

SILVER SLED · February 1, 2019

Mine has been awesome. If I were to build an old hot rod, I'd put one in it,

mookdoc6 · February 1, 2019

Mine had reprogramming and such has the normal firmer shifts on cold start...banged into gear for first 5K miles? No issues other than it's loud kicking down to a stop sometimes?

ammoaddict · February 2, 2019

Mine has 1500 miles and no issues yet.

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SSchup · February 2, 2019

9100 miles and perfect so far.

qwank · February 2, 2019

Everyone with an 8 speed needs to go and get your trans fluid Flushed and replaced with the new Non- hydroscopic fluid. The reason the transmissions shudder is because the fluid they used is hydroscopic like brake fluid, which means it will absorb water and moisture. Unlike a hydraulic brake system which is sealed, transmissions are vented, allowing moisture to build up in the fluid. The new fluid they have prevents this. Both versions of the 8 speed HP fluid are made by Mobile One. The old bottles have a gray label on them, the new bottles are gray and blue labeled.

Edited February 2, 2019 by qwank

Harold Rutherford · February 2, 2019

I traded my 2016 Sierra with a 6 speed transmission that was rough shifting for a new 2018 Sierra with the 8 speed transmission, other than slipping when first starting off in morning and a whining siren sound in the middle gears it is much much better than the 6 speed. I actually went in October 2018 to trade for the new 2019 Sierra SLT but was turned off by the much higher price and ugly black or dark walnut slate interior colors. I ended up with a 2019 Crystal Red Metallic with cocoa dune leather and much happier.

midwestdenaliguy · February 2, 2019

2016 Sierra - 6.2L, CC, short bed. 8 speed has been fine for 77k miles for me. It had an occasional 'hiccup' where it would shift a little hard between 2nd and 3rd, but that went away with a tune. Even before that though I didn't think it was that hard of a shift. Recently had it flushed and all is well.

SS502 · February 3, 2019

So far there is 80% with no problems. 20% that have had issues with only 33% of the 20% not yet fixed. Those are pretty good stats....so far.

CadillacLuke24 · February 3, 2019

On 2/1/2019 at 8:29 PM, qwank said:

Everyone with an 8 speed needs to go and get your trans fluid Flushed and replaced with the new Non- hydroscopic fluid. The reason the transmissions shudder is because the fluid they used is hydroscopic like brake fluid, which means it will absorb water and moisture. Unlike a hydraulic brake system which is sealed, transmissions are vented, allowing moisture to build up in the fluid. The new fluid they have prevents this. Both versions of the 8 speed HP fluid are made by Mobile One. The old bottles have a gray label on them, the new bottles are gray and blue labeled.

qwank is there a new part number for the non-hydroscopic fluid? Or is the 19353429 number for the Mobil LV HP I've been finding on Google still valid?

ammoaddict · February 3, 2019

So far there is 80% with no problems. 20% that have had issues with only 33% of the 20% not yet fixed. Those are pretty good stats....so far.

You're talking about just on this thread, correct?

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SS502 · February 3, 2019

3 minutes ago, ammoaddict said:

You're talking about just on this thread, correct?

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Yes, I posted it in this thread because I am referring to this thread ? I doubt anyone (other than GM) know the reported cases of transmission problems. Personally, I’d rather forego the fuel mileage and have the 4 speed that my 2008 Avalanche had...oh and that post I made is only accurate up to the point I posted it, every time someone else posts the numbers (albeit slightly) will change.

Edited February 3, 2019 by SS502

M1ck3y · February 3, 2019

On ‎01‎/‎02‎/‎2019 at 8:29 PM, qwank said:

Everyone with an 8 speed needs to go and get your trans fluid Flushed and replaced with the new Non- hydroscopic fluid. The reason the transmissions shudder is because the fluid they used is hydroscopic like brake fluid, which means it will absorb water and moisture. Unlike a hydraulic brake system which is sealed, transmissions are vented, allowing moisture to build up in the fluid. The new fluid they have prevents this. Both versions of the 8 speed HP fluid are made by Mobile One. The old bottles have a gray label on them, the new bottles are gray and blue labeled.

If this was true gm would do a recall. Have they? Because if they have I'm going in to get this done, otherwise I'm not going to waste time at the dealer arguing about how a transmission is supposed to operate.

Edited February 3, 2019 by M1ck3y

mjm-1957 · February 3, 2019

The reason that the TCC shudders is because it is never locked up 100%. It is designed to slip between 0-50 rpm at all times. Also TCC is applied earlier and earlier to try and achieve better fuel economy. TCC never applied this early in older vehicles. And when it came on it was 0 slip. Allison still locks there TCC 100% and it is held off until 3rd gear. What do you expect to happen when you slip a cltuch? I have been a line mechanic in a GM dealer since 1978 and have done just about every transmission GM has come out with from the Power Glide all the way up to the 8L90E , That transmission is a light duty, poorly engineered failure waiting to happen.It' s not a case of if your going to have a problem, but rather when. You would be doing yourself a big favor by purchasing a good extended warranty if you own one of these. The powertrain coverage was lowered to 60,000 miles in 2016.Not bashing, just speaking about what I see every day..........

mjm-1957 · February 3, 2019

The reason that the TCC shudders is because it is never locked up 100%. It is designed to slip between 0-50 rpm at all times. Also TCC is applied earlier and earlier to try and achieve better fuel economy. TCC never applied this early in older vehicles. And when it came on it was 0 slip. Allison still locks there TCC 100% and it is held off until 3rd gear. What do you expect to happen when you slip a clutch? I have been a line mechanic in a GM dealer since 1978 and have done just about every transmission GM has come out with from the Power Glide all the way up to the 8L90E , That transmission is a light duty, poorly engineered failure waiting to happen.It' s not a case of if your going to have a problem, but rather when. You would be doing yourself a big favor by purchasing a good extended warranty if you own one of these. The powertrain coverage was lowered to 60,000 miles in 2016.Not bashing, just speaking about what I see every day..........