Grind noise with quick Stop/Start

[SilveradoRST]

Anyone else get a grinding noise from underneath when you have a quick stop and go situation (1-2 seconds on the brake) and it triggers the Auto Stop/Start?  Grinding noise happens when the engine starts up from the auto stop.  No gas.  Just lifting foot off the brakes and grind noise. Happened maybe 2-3 times.  Never happens if I stop longer, past 1-2 seconds.  That’s my transmission getting a shave, right?  Under 5000km on it.  5.3 8 speed.  
 

Obviously, I will now be conscious and try to hold my brakes a bit longer if I see the Auto Stop kicked in. 

Edited October 7, 2019 by SilveradoRST

[oldmann]

39 minutes ago, SilveradoRST said:

Anyone else get a grinding noise from underneath when you have a quick stop and go situation (1-2 seconds on the brake) and it triggers the Auto Stop/Start?  Grinding noise happens when the engine starts up from the auto stop.  No gas.  Just lifting foot off the brakes and grind noise. Happened maybe 2-3 times.  Never happens if I stop longer, past 1-2 seconds.  That’s my transmission getting a shave, right?  Under 5000km on it.  5.3 8 speed.  
 

Obviously, I will now be conscious and try to hold my brakes a bit longer if I see the Auto Stop kicked in. 

No, I have never had that happen yet.  

[newdude]

Don't wait too long to get that looked at...otherwise it might not start back up one day. 

 

 

Edited October 7, 2019 by newdude

[garagerog]

As newdude said, get it looked at. I'm wondering from the description if the starter isn't trying to engage while the flexplate still has some rotation.

[SilveradoRST]

After thinking more about what the sound sounds like, it sounds similar to when you hold the key (old school, not push button) in the ignition a bit too long after the car/truck has already started.  
 

Thanks for the bulletin newdude.  And everyone who took their time to reply.  
 

I will try and get it checked soon.  

[AlaskaErik]

Auto Stop Eliminator.  Permanently keep auto stop turned off.  

[Thomcat]

Depends upon the reading of the speedometer, i.e. if the speedometer reading is 0 mph for a two second stop or whether not fully stopped with the speedometer reading 1-2 mph. Under these circumstances I'll hear the noise, but not a grinding noise, of the starter motor disengaging from the flexplate. The s/s system is not like a conventional starter arrangement - the starter uses a split solenoid and the front part will engage the flexplate while the engine is still spinning at around 4 mph and below during a stop. If the brake pedal is released while it is engaging and the engine is still spinning above 0 rpm and partially stopped, you'll get a different noise than when the motor is restarted after it has reached 0 rpm when fully stopped. If looking for it I can hear that mechanical noise, but it is not like the grinding noise when trying to engage the starter motor on the older vehicles while the engine is still spinning (newer ECU controlled vehicles without s/s won't let you do something stupid like that anyway and will not engage the starter motor on a running engine. Operation of the starter motor split solenoid in a s/s system is described in many articles,e.g.

 

https://gm-techlink.com/?p=8493

 

If a true grinding noise, likely a problem with the split solenoid in the starter.

Edited October 7, 2019 by Thomcat
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[newdude]

1 hour ago, SilveradoRST said:

After thinking more about what the sound sounds like, it sounds similar to when you hold the key (old school, not push button) in the ignition a bit too long after the car/truck has already started.  
 

Thanks for the bulletin newdude.  And everyone who took their time to reply.  
 

I will try and get it checked soon.  

 

I did delete that as it was for the Turbo 4 cylinder.  So disregard that. 

[JonathanGMC]

Hello, new poster here, I found this thread and have a similar thing with my 2020 Sierra AT4. Under hard braking as I get to 15 mph to zero, I have a really painful grinding sound. It's a deep grinding sound, not like metal-on-metal train car sounds. What is very odd is that (I think) it doesn't happen with Auto Stop/Start disabled... which makes no sense to me (I thought it was the brakes making the sound), but so far in my testing it seems to be the case. It's difficult to reproduce the problem though.

[jtl1985]

my truck does it every so often. its loud too. talked with dealer and they said nothing except for its weird. but they have not heard it. its a stipend go situation and I don't have time to just leave it with them to try to get it to repeat. that auto stop function is stupid and should be the other way around. if you want to use it then you hit the button to turn it on, not have it engaged every time you start your vehicle.