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Discussion Starter · #1 ·
Hey, so last Friday my automatic transmission finally blew out when I was on the highway at 105k miles and wouldn't shift past 3rd, had AAA tow it to Chevy when service was closed and had them set me up in a brand new 2015 Silverado off the lot because they had no rental vehicles left, been driving that for 5 days and Chevy finally got back to me saying the solenoid in the TCM jammed up and snapped the clutch plates in the transmission so they'll be replacing most of the parts in the transmission, so that leads me to my question.


Is there a break-in period? Can I go 80MPH like I normally do on the highway right out the gate or do I have to go 60 mph and not rev it past lets say 4k for 1000 miles? Chevy said no to a break-in but I don't exactly trust their knowledge seeing how this is the 2nd transmission after it blew out at 20-25k.
 

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I can't say as I've heard of a break-in for transmissions. It's usually for engines. Mostly to get the piston rings settled in.
 
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I would keep it below 3000 RPM for the first 1,000 miles.
 

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Then don't keep your RPMs up there. I would avoid hard accelerations as those put stress on the transmission when it shifts.
 

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Discussion Starter · #10 ·
Then don't keep your RPMs up there. I would avoid hard accelerations as those put stress on the transmission when it shifts.
what exactly would I be breaking in? Plates and gears or just lubricating everything like seals etc? Wouldn't all of that be done during the rebuild and first turn over? I'm just curious.
 

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A auto box does not require a formal break in but gentle driving can extend its service life.

Specifically, with each upshift, the clutch plates are 'burnishing in'……that means the high spots that exist on new friction discs are being smoothed off.
If you are hammering on it during this period (about 100 miles btw) the disc faces develop hot spots that may promote slippage as the miles accrue.

Essentially, being gentle further insures the potential for maximum service life……same as wearing in new brake shoes and pads.

Rob
 

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A auto box does not require a formal break in but gentle driving can extend its service life.

Specifically, with each upshift, the clutch plates are 'burnishing in'……that means the high spots that exist on new friction discs are being smoothed off.
If you are hammering on it during this period (about 100 miles btw) the disc faces develop hot spots that may promote slippage as the miles accrue.

Essentially, being gentle further insures the potential for maximum service life……same as wearing in new brake shoes and pads.

Rob
What he said. But I would say the first 200 miles. 500 miles if you really want to be prudent.

I'm starting to wonder if your driving style led to your transmission failure?
 

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Discussion Starter · #13 ·
What he said. But I would say the first 200 miles. 500 miles if you really want to be prudent.

I'm starting to wonder if your driving style led to your transmission failure?
I thought that too but after doing further diagnostics at Chevy, they found out the speed sensor going out more than 4 times was the cause of the transmission going out prematurely. That's why it went out at 20-25k after I got the car brand new with 0 miles on it from Chevy, because the speed sensor blew out after they updated my transmission software and caused the transmission to blow out the plates.


200-500 miles seems to make sense for a break-in
 

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It's no break in for these also make sure they are installing a new Tcm and not just cleaning out the old one causing more issues later on. Also was it the 2-3 wave plates that failed that's a known issue with the 6t40. Mines went out at 95k
 

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Discussion Starter · #15 ·
It's no break in for these also make sure they are installing a new Tcm and not just cleaning out the old one causing more issues later on. Also was it the 2-3 wave plates that failed that's a known issue with the 6t40. Mines went out at 95k
Yea the 2-3, should I expect it to go out again or do they replace it with a better quality plate?
 

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Discussion Starter · #16 · (Edited)
Just got the car back after 7 days, the tranny feels nice and tight, there was a small minor faint jerk when downshifting once and upshifting once, but I didn't feel it the rest of the drive after. I'm guessing there's a little bit of slip in one of the lower gear plates from driving the transmission with a jerk in it for almost 50k miles. The transmission has never felt this good even when I got the car brand new off the truck, I'm really starting to think I got a lemon from the factory that just had a whole lot of unlucky problems.
 

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Yeah transmission seems to be a winner, just picked my car up $3000 later for failed solenoid a and TCM. 129,000 miles highway driving, no love just luck of the draw. Glad you were take. Care of by GM


Sent from my iPhone 6 using Tapatalk
 

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Just got the car back after 7 days, the tranny feels nice and tight, there was a small minor faint jerk when downshifting once and upshifting once, but I didn't feel it the rest of the drive after. I'm guessing there's a little bit of slip in one of the lower gear plates from driving the transmission with a jerk in it for almost 50k miles. The transmission has never felt this good even when I got the car brand new off the truck, I'm really starting to think I got a lemon from the factory that just had a whole lot of unlucky problems.
The transmission is a smart one and has to adapt to your driving habits and calibrate itself on apply pressures the first few miles of driving
 

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Just got the car back after 7 days, the tranny feels nice and tight, there was a small minor faint jerk when downshifting once and upshifting once, but I didn't feel it the rest of the drive after. I'm guessing there's a little bit of slip in one of the lower gear plates from driving the transmission with a jerk in it for almost 50k miles. The transmission has never felt this good even when I got the car brand new off the truck, I'm really starting to think I got a lemon from the factory that just had a whole lot of unlucky problems.
did they replace or just clean the TCM? Also the plates are a different quality
 
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