Rattle noise after trans service - only when cold-ish and under light throttle.....hmmm

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iboughtatahoe23

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Yes, it was similar to that. Usually from stop and go, or turning and accelerating. It ended up being a quart low on fluid after they did the service......Idiots
man that’s strange. I had my fluid changed in march and have had some intermittent shifting issues and then that grind noise. Maybe time to call the dealership and make sure they filled it.

I will also check my fluid thanks.
 

iboughtatahoe23

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man that’s strange. I had my fluid changed in march and have had some intermittent shifting issues and then that grind noise. Maybe time to call the dealership and make sure they filled it.

I will also check my fluid thanks.
And i before I had it changed by dealer I told them I’m having shifting issues. They said my fluid was low and dirty after the salesman told me it was good on fluids. So two different stories there.

I have a hard time believing either.
 
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Yes, it was similar to that. Usually from stop and go, or turning and accelerating. It ended up being a quart low on fluid after they did the service......Idiots
Not to cause panic but I wonder if your pump was partially cavitating which was the noise you were hearing. Once the fluid level was restored to full, it stopped as there was no more air displacing the fluid inside the pump. Typically being only a quart low wouldn't cause this but it's also possible you were a lot more than just one (1) quart shy of full or those units are super sensitive to fluid levels. In your trans, the pump itself is actually set back a bit from the very front of the case, not directly in front like pretty much all GM transmissions made prior so the location of the sound makes sense. Also pumps can make a variety of different sounding noises but the common themes are 'knocking', 'chattering', 'ticking', 'rattling', etc.

Here's the pump relative to the front of the transmission (looks a little like a power steering pump), which is towards the right hand side of the image.
1690314844917.png
 
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B-train

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Not to cause panic but I wonder if your pump was partially cavitating which was the noise you were hearing. Once the fluid level was restored to full, it stopped as there was no more air displacing the fluid inside the pump. Typically being only a quart low wouldn't cause this but it's also possible you were a lot more than just one (1) quart shy of full or those units are super sensitive to fluid levels. In your trans, the pump itself is actually set back a bit from the very front of the case, not directly in front like pretty much all GM transmissions made prior so the location of the sound makes sense. Also pumps can make a variety of different sounding noises but the common themes are 'knocking', 'chattering', 'ticking', 'rattling', etc.

Here's the pump relative to the front of the transmission (looks a little like a power steering pump), which is towards the right hand side of the image.
View attachment 404714
I would agree with you, but it wasn't constant and would happen when cold and when the fluid sloshed around. It was definitely pump cavitation. This is why I will do my own stuff from now on......not some flat rate bafoon hoping for no come-backs.

2017, 8 speed is what I had the issue on. I'm assuming the same as OP but not certain. It's interesting how sensitive these new transmissions are. I miss the 90's and early 2000's.

Thank you for the pic and explanation BTW!
 
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I would agree with you, but it wasn't constant and would happen when cold and when the fluid sloshed around. It was definitely pump cavitation. This is why I will do my own stuff from now on......not some flat rate bafoon hoping for no come-backs.

2017, 8 speed is what I had the issue on. I'm assuming the same as OP but not certain. It's interesting how sensitive these new transmissions are. I miss the 90's and early 2000's.

Thank you for the pic and explanation BTW!
You're welcome, B-Train and agree - the legacy three and four speeds were a lot less complex from a command and control stand point and flat-raters couldn't care less (ive rebuilt a lot of flat rate jobs from customers trying to save a buck).

I would also assume it's the same for the OP'er as well ;)
 

iboughtatahoe23

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Also checked my fluid. And it’s good…
I would agree with you, but it wasn't constant and would happen when cold and when the fluid sloshed around. It was definitely pump cavitation. This is why I will do my own stuff from now on......not some flat rate bafoon hoping for no come-backs.

2017, 8 speed is what I had the issue on. I'm assuming the same as OP but not certain. It's interesting how sensitive these new transmissions are. I miss the 90's and early 2000's.

Thank you for the pic and explanation BTW!
So it was just low fluid for you?
 
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B-train

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Yes. The 8 speed has a stand tube, no dipstick (stupid and cheap in my book). When they did the flush, the tech didn't check the level after it was warmed up and it ended up being low. Gotta love flat rate
 

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