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"Revised" 6-speed

MotoMedic

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MotoMedic Senior Enthusiast

MotoMedic

Posted
Posted

I read somewhere that the 6-speed in the 2014's got updated/tweaked (shift points, mapping, etc..). I had the 4-speed in my previous '07 Sierra, so I can't comment about any changes but I have noticed something that is REALLY bugging me! When coming to a normal red light stop from say 50 MPH the truck downshifts at roughly each 10 MPH interval. It seems like each shift is too soon and engine/wheel speed is too high for gear which results in lurch/jerk of brief acceleration while you're trying to brake. Almost feels like a manual transmission downshift that you had blipped the throttle a little much during.

Anyone have a similar experience?

Is this normal for the 6-speed?

If yes, is there any program/tune to correct this behavior???

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RyanbabZ71 Senior Enthusiast

RyanbabZ71

Posted
Posted

All I can say is give it some time. How many miles do you have? It's an adaptive transmission so it needs to learn your driving style over time

 

 

Ryan

 

 

Stex Senior Enthusiast

Stex

Posted
Posted

Do the revs jump when it does this? How much? As Ryan said it maybe just too new. Try some manual shifting.

Natek Enthusiast

Natek

Posted
Posted

Mine shifted like it had 200,000 miles on it when I bought it. It took about 2000 miles to get smooth. Now it's hard to even notice it's shifting.

MotoMedic Senior Enthusiast

MotoMedic

Posted
  • Author
Posted

Less than 300 miles.

Thanks for the feedback. Glad to have this forum b/c now I know my only complaint is a temporary one.. Sweet!!

MotoMedic Senior Enthusiast

MotoMedic

Posted
  • Author
Posted

Do the revs jump when it does this? How much?

 

Yes, as I'm slowing down, each downshift will cause the RPM's to briefly jump from around 500-700 to 1000-1200. You can feel the pulse in power compete against the brakes when pressing the pedal normal. Under harder braking, I haven't noticed any pulse but that's likely b/c the vehicle decelerates so rapidly.

Stex Senior Enthusiast

Stex

Posted
Posted

500 rev jump seems like one gear down and the 1000-1200 rev jump sounds like a two gear drop. They may have tune the tcm for more aggressive downshifts but that would be counter productive for better mpg. My 09 will lug down to 40mph in 6th before downshifting and bucks when it does such.

 

If it keeps it up and dealer is close, I would have them look at it. Drive in manual and see how it down shifts in manual (on its own with no input from you on the shift lever button).

gbieber05 Enthusiast

gbieber05

Posted
Posted

Motomedic I don't seem to have that problem. All smooth shifting for me. I would take it by the local dealer let them check it.

Stex Senior Enthusiast

Stex

Posted
Posted

Your 4 speed was not a clutch to clutch transmission like the 6 spd is. Totally normal.

Not sure what you are saying as I am not a tech...my 09 does not do this but it does buck on decal around 50-40...ops seems to rev to high on down shifts?
2017HD Enthusiast

2017HD

Posted
Posted

From what I have read, the new 6 sp has a form of grade braking in normal mode (not tow haul)That would account for the downshifting - as for the transmission be adaptive, they are and often take a couple of weeks of normal driving to settle in.

MotoMedic Senior Enthusiast

MotoMedic

Posted
  • Author
Posted

I'm going to give it at least 2000 miles. If it persists past that, I'll swing by the dealer.

Daryl LBZ Senior Enthusiast

Daryl LBZ

Posted
Posted

When I got my current truck I had a shudder when I would take off slow from a start when I would first drive it for the day. As I put more miles on the truck it got better and better and eventually went away. My guess is what your feeling will get better with mileage.

jdelrizzle Enthusiast

jdelrizzle

Posted
Posted

From what I have read, the new 6 sp has a form of grade braking in normal mode (not tow haul)That would account for the downshifting - as for the transmission be adaptive, they are and often take a couple of weeks of normal driving to settle in.

My 2013 has grade braking

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