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Harsh Downshifts - is there a fix?

njk4o5
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njk4o5 Enthusiast

njk4o5

Posted
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my 14 high country has the hard downshift syndrome. bad from the 3-2 shift and horrible from 2-1 nearly screeches the tires. Ive taken it to the dealer twice now, torque converter replaced first time. same problem, then valve bodies replaced, same problem.

 

so many threads about this issue...where is the fix? I've read countless threads and no one could seem to make this issue go away. aftermarket tuning is out of the question for me. not going to void warranty.

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Jwc
Jwc

So does anyone think hard down shift is what could have caused my torque converter to come apart?

MGIG
MGIG
wetcoaster Enthusiast

wetcoaster

Posted
Posted

Lol. No GM doesn't care that a large portion doesn't like the operation of the tranny

 

Sent from my SM-G903W using Tapatalk

njk4o5 Enthusiast

njk4o5

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theres no way this is normal. my truck does it intermittently 75% of the time. the other 25% of the time it drives as it should

Dunc Enthusiast

Dunc

Posted
Posted (edited)

http://www.gm-trucks.com/forums/topic/195861-my-8l90e-is-finally-fixed/

 

Cliffs: Have them lookup TSB# 14-07-30-001G or find the same if you have the the 6-speed. Even after a new transmission was installed for me I had very harsh downshifts.They performed 14-07-30-001F on mine and the problems instantly went away. I have not had a delayed engagement, harsh shift into gear, or harsh downshift since this was done on 12/29/16.

Edited by Dunc
scottl1346 Enthusiast

scottl1346

Posted
Posted

having the same issues but the only tsb's i have found are only mentioning the 8 speed why would GM fix only the 8 speeds when these issues started with the 6 speeds and no fix for us. my dealer could careless and play the its operating as designed card i don't think down shifts should make passengers lunge foreword but that just me and i get a good bang/clunk right around 30mph up or downshift.

sk Senior Enthusiast

sk

Posted
Posted (edited)

Yeah that TSB is only for the 8-speed vehicles. Good luck getting your dealer to apply it to your truck if it's a 6-speed (there is not a similar TSB for the 6-speed).

Edited by sk
2018GMC Senior Enthusiast

2018GMC

Posted
Posted

If you don't mind possibly voiding your warranty or are out of warranty a performance tune would probably cure the erratic shifts. I'm sure some people with tunes will chime in shortly...

njk4o5 Enthusiast

njk4o5

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If you don't mind possibly voiding your warranty or are out of warranty a performance tune would probably cure the erratic shifts. I'm sure some people with tunes will chime in shortly...

whats the point of a warranty then? I agree with you the aftermarket tune would fix it. now that's $600 out of my own pocket to fix what should have been fixed for free under warranty.

2018GMC Senior Enthusiast

2018GMC

Posted
Posted

Yeah, it's BS that GM says its operating normally and won't do anything. I guess most people just deal with it, tune it, or get rid of truck.

 

I thought someone had a dealer do a fast relearn and it helped his shifting issues.

alkaspeltzar Enthusiast

alkaspeltzar

Posted
Posted

my 14 high country has the hard downshift syndrome. bad from the 3-2 shift and horrible from 2-1 nearly screeches the tires. Ive taken it to the dealer twice now, torque converter replaced first time. same problem, then valve bodies replaced, same problem.

 

so many threads about this issue...where is the fix? I've read countless threads and no one could seem to make this issue go away. aftermarket tuning is out of the question for me. not going to void warranty.

 

When you say harsh downshifts, can you explain? My truck I notice if I brake hard, downshifts hard. Brake slow and soft, downshifts soft. it is like the programming of the transmission is set to grade brake down even under normal driving conditions.

 

Also, what RPMS are you seeing down shifts occur? Mine usually are around 800-900rpm then rise to 1000-1200rpm, until down around 800rpm, then repeat for each lower gear except first, where it goes to idle

 

I think my tranny as it has aged has got more clunky. 70+K and things just are not as smooth

njk4o5 Enthusiast

njk4o5

Posted
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When you say harsh downshifts, can you explain? My truck I notice if I brake hard, downshifts hard. Brake slow and soft, downshifts soft. it is like the programming of the transmission is set to grade brake down even under normal driving conditions.

 

Also, what RPMS are you seeing down shifts occur? Mine usually are around 800-900rpm then rise to 1000-1200rpm, until down around 800rpm, then repeat for each lower gear except first, where it goes to idle

 

I think my tranny as it has aged has got more clunky. 70+K and things just are not as smooth

mine does it at about those same rpms and rises to those same rpms, but it will do it no matter how hard I brake. the weirdest part is some days it doesn't do it, other days it does.

 

my truck has 96,500 on it. dealer just did the torque converter and valve bodies this week. I would think if GM knew a tune would fix it, they would make a tune instead of replacing expensive tranny parts. but hey I don't care what they do to try and fix it since its under warranty

alkaspeltzar Enthusiast

alkaspeltzar

Posted
Posted

mine does it at about those same rpms and rises to those same rpms, but it will do it no matter how hard I brake. the weirdest part is some days it doesn't do it, other days it does.

 

my truck has 96,500 on it. dealer just did the torque converter and valve bodies this week. I would think if GM knew a tune would fix it, they would make a tune instead of replacing expensive tranny parts. but hey I don't care what they do to try and fix it since its under warranty

did the torque converter or valve body make it anybetter? or where they smoked already?

 

These things are tuned for fuel saving which is awesome to some degree. I know plenty of ford, dodge and tundra people out there looking silly with their fuel mileage. However, I feel it is saving fuel although putting extra wear and tear on good trucks

njk4o5 Enthusiast

njk4o5

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no change at all. matter of fact it did the usual downshift as I pulled out of the service lot each time I picked it up. banged a U-turn and dropped it back off. now they are saying they've tried it all and theres no fix...but they agree somethings wrong. im not sue what to do here and my warranty is almost up.

 

I get the whole tuned for MPG thing, but the dam truck doesn't even get good mpg lol. my 2004 Silverado I traded in for this 2014 had 212,000 on it and got 19mpg religiously. this shitbox only gets 17-18

rangerhgm Enthusiast

rangerhgm

Posted
Posted (edited)

 

When you say harsh downshifts, can you explain? My truck I notice if I brake hard, downshifts hard. Brake slow and soft, downshifts soft. it is like the programming of the transmission is set to grade brake down even under normal driving conditions.

 

Also, what RPMS are you seeing down shifts occur? Mine usually are around 800-900rpm then rise to 1000-1200rpm, until down around 800rpm, then repeat for each lower gear except first, where it goes to idle

 

I think my tranny as it has aged has got more clunky. 70+K and things just are not as smooth

 

 

I have ~2500 on my truck and just took an extended trip a week ago and noticed the hard downshift for the first time. Until this trip I hadn't done and hard braking, but I did notice it a couple times during the trip.

Edited by rangerhgm

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