Hard down shift

Luckyfd · February 10, 2020

Every now and again, when coming to a stop, the truck goes from 3-1 HARD! I’m am not going from brake to gas only braking. Chevy blew me off but I have seen on google search this is a common problem. I’m curious to see if anyone has had it fixed...

TXGREEK · February 10, 2020

Every now and again, when coming to a stop, the truck goes from 3-1 HARD! I’m am not going from brake to gas only braking. Chevy blew me off but I have seen on google search this is a common problem. I’m curious to see if anyone has had it fixed...

Can you PLEASE be more specific, Year, Model, Trim, Motor, Transformation etc etc etc

Sent from Above

flyingfool · February 10, 2020

you can purchase from EFI live a new TCU file for the transmission shiftpoints. unless its still locked out from tuning?

Edited February 10, 2020 by flyingfool

BlancoSilverado · February 10, 2020

How do you know its a 3-1 shift and not a 2-1 shift?

Luckyfd · February 10, 2020

45 minutes ago, TXGREEK said:

Can you PLEASE be more specific, Year, Model, Trim, Motor, Transformation etc etc etc

Sent from Above

2019 Chevy Silverado LT 5.3 8 speed

Luckyfd · February 10, 2020

13 minutes ago, BlancoSilverado said:

How do you know its a 3-1 shift and not a 2-1 shift?

I don’t. It feels like 3 hard down shifts. But it could be 2. When I researched this online it tended to come up more on a 3-2-1 downshift problem.

madconcept · February 12, 2020

Noticed a bit of this myself last night slowing to stop.

Also going from reverse to drive these trucks are kinda finicky too.

If you even touch the gas before the truck has fully clicked into drive it’ll slam.

2019 Sierra 5.3 8 speed(early build with older style fluid)

Thomcat · February 12, 2020

Whole topic boils down to a "So what?"

It a piece of machinery operating with a number of temperature, mechanical and electronic input variables, plus a "self learning" feature that makes the whole system variable as a function of time and mileage. Not to mention an ever increasing number of multiple drum gearsets jammed into the same size case with one way and locking clutches to save mileage over its ancestors. Bands are constantly braking and releasing drumsets and depending upon the gear, multiple combinations have to occur simultaneously to get a smooth shiftpoint. So yeah, on an infrequent occasion a shiftpoint will screw up and you'll get a hard shift point or delayed downshift.....even a hang or two on the first 1-2 a sub freezing first upshift until fluid gets heated......so what?

Problem? Want a problem, then talk about a real problem like : no go situation, locked in 2nd limp in mode, band slippage, engine flaring, seal leakage, fluid burning, failure to upshift, metallic noises in the bell housing, etc......not an occasional hard shift point......I've a late build 8 speed with the Mobil1 HP and I occasionally get a hard shift point......again, so what, a quirk not a defect.

Want a really smooth tranny like my '74 Impala Custom? Toss out 2 drumsets to make a 4 speed, throw out all the EPA mileage crap like sprague clutches and locking torque convertors, install mechanical linkage connecting carb opening to tranny throttle, dump the electronics and install mechanical governors, and design the shiftpoints with a wicked gear overlap to mask drum set transfer.....and as long as the 454 was running smooth the tranny would shift smooth as silk first time, every time......and get a stinking 5-6 mpg on a good day!

Silverado4x4 · February 13, 2020

10 hours ago, Thomcat said:

Whole topic boils down to a "So what?"

It a piece of machinery operating with a number of temperature, mechanical and electronic input variables, plus a "self learning" feature that makes the whole system variable as a function of time and mileage. Not to mention an ever increasing number of multiple drum gearsets jammed into the same size case with one way and locking clutches to save mileage over its ancestors. Bands are constantly braking and releasing drumsets and depending upon the gear, multiple combinations have to occur simultaneously to get a smooth shiftpoint. So yeah, on an infrequent occasion a shiftpoint will screw up and you'll get a hard shift point or delayed downshift.....even a hang or two on the first 1-2 a sub freezing first upshift until fluid gets heated......so what?

Problem? Want a problem, then talk about a real problem like : no go situation, locked in 2nd limp in mode, band slippage, engine flaring, seal leakage, fluid burning, failure to upshift, metallic noises in the bell housing, etc......not an occasional hard shift point......I've a late build 8 speed with the Mobil1 HP and I occasionally get a hard shift point......again, so what, a quirk not a defect.

Want a really smooth tranny like my '74 Impala Custom? Toss out 2 drumsets to make a 4 speed, throw out all the EPA mileage crap like sprague clutches and locking torque convertors, install mechanical linkage connecting carb opening to tranny throttle, dump the electronics and install mechanical governors, and design the shiftpoints with a wicked gear overlap to mask drum set transfer.....and as long as the 454 was running smooth the tranny would shift smooth as silk first time, every time......and get a stinking 5-6 mpg on a good day!

Very good post Tom and I agree 100%. I get it from time to time and it all depends on what iam doing with the truck at that time meaning did I just take off from a stop with very lite throttle then let off and it down shifted again then sometimes it will do it, big deal. Sometimes when taking off and truck shifts to 2nd or 3rd or maybe 4th to 5th and just before it shifts to another gear I let off the gas and it will bump to the higher gear due to trans pressure again so what.

What really is ridicules is some people complain that they paid 70 grand for a vehicle and expect it to be trouble free due to the money spent well that 70 grand truck is no different then a $25,000 WT truck its just the 70 grand truck has more options. Its not built with workers wearing white gloves in a dust free environment and getting special parts.

I think a lot of people didn't drive back in the 70s and had to deal with the issues new cars had back then and you dealt with it, manual choke let it warm up for 10-15 minutes before driving because it will conk out when the gas was pressed, 2 speed transmissions no AC, AM radio, sealed beam headlights then would project 40 feet down the road, roll up windows, Bias tires that would flat spot sitting in cold weather and shake like crazy till warmed up, pump the gas 3-4 times to get it to start, wind noise around the windows with then rolled up, the list goes on.

A lot of these post I just shake my head and move on.

Edited February 13, 2020 by Silverado4x4

RichieC · February 15, 2020

To the OP. This is a legit subject and there is a solution, or at least there was for me. I was experiencing the same condition and the dealer found a bulletin 19-NA-244 that describes the exact problem. The bulletin is to reprogram TCM due to a software anomaly. They did this to my truck (2019 5.3 8 speed LTZ) and at first the truck almost seemed to have no downshift, like you threw it in neutral, but within the first few trips I no longer noticed this, possibly due to self learning? What I can say is I have not experienced the harsh downshift since.

I did find an earlier thread on this before having mine dealt with where it was described as being hit from behind, I think thats excessive but it was very noticeable and to me as well and was something I felt was not right. Was it something catastrophic, no. Was it annoying, definitely.

"So what?" so how does this have anything to do with what other problems are more prominent in comparison or what you paid in relation to your expectations of a correctly operating vehicle. I dont know how comparing 40 year old vehicles justifies a downshift on a new vehicle that feels like you side stepped the clutch while rolling to a stop too fast in something that is 40 years old with a bunch of worn out driveline components. Technology and advancements shouldnt equate to a poorly functioning product, be it a 70k truck or a $20 piece of whatever, and it shouldnt mean you just accept problems.

Hope this information is what you were looking for and possibly helps you with something to take to your dealer.

Thomcat · February 16, 2020

On 2/12/2020 at 7:30 PM, Silverado4x4 said:

Very good post Tom and I agree 100%. I get it from time to time and it all depends on what iam doing with the truck at that time meaning did I just take off from a stop with very lite throttle then let off and it down shifted again then sometimes it will do it, big deal. Sometimes when taking off and truck shifts to 2nd or 3rd or maybe 4th to 5th and just before it shifts to another gear I let off the gas and it will bump to the higher gear due to trans pressure again so what.

What really is ridicules is some people complain that they paid 70 grand for a vehicle and expect it to be trouble free due to the money spent well that 70 grand truck is no different then a $25,000 WT truck its just the 70 grand truck has more options. Its not built with workers wearing white gloves in a dust free environment and getting special parts.

I think a lot of people didn't drive back in the 70s and had to deal with the issues new cars had back then and you dealt with it, manual choke let it warm up for 10-15 minutes before driving because it will conk out when the gas was pressed, 2 speed transmissions no AC, AM radio, sealed beam headlights then would project 40 feet down the road, roll up windows, Bias tires that would flat spot sitting in cold weather and shake like crazy till warmed up, pump the gas 3-4 times to get it to start, wind noise around the windows with then rolled up, the list goes on.

Here's another quirk on the 8 speed which I find meaningless. The first hard 1-2 shift after an overnight cold......sometimes a momentary hang and a bump with no slippage. I've read the article and have the Mobil1 fluid

https://gm-techlink.com/?p=11127

Mentions the test should be done with a tranny temp above 122F. Just for the heck of it on sub 32F days auto-started and warmed the truck first until tranny was above 120F. Tried it on two occasions and found the first 1-2 shift was smooth as silk. Apparently oil viscosity is a function of temperature and can effect shift quality - so there's another point that is a quirk, not a defect that doesn't bother me.

Luckyfd · March 1, 2020

On 2/15/2020 at 1:21 PM, RichieC said:

To the OP. This is a legit subject and there is a solution, or at least there was for me. I was experiencing the same condition and the dealer found a bulletin 19-NA-244 that describes the exact problem. The bulletin is to reprogram TCM due to a software anomaly. They did this to my truck (2019 5.3 8 speed LTZ) and at first the truck almost seemed to have no downshift, like you threw it in neutral, but within the first few trips I no longer noticed this, possibly due to self learning? What I can say is I have not experienced the harsh downshift since.

I did find an earlier thread on this before having mine dealt with where it was described as being hit from behind, I think thats excessive but it was very noticeable and to me as well and was something I felt was not right. Was it something catastrophic, no. Was it annoying, definitely.

"So what?" so how does this have anything to do with what other problems are more prominent in comparison or what you paid in relation to your expectations of a correctly operating vehicle. I dont know how comparing 40 year old vehicles justifies a downshift on a new vehicle that feels like you side stepped the clutch while rolling to a stop too fast in something that is 40 years old with a bunch of worn out driveline components. Technology and advancements shouldnt equate to a poorly functioning product, be it a 70k truck or a $20 piece of whatever, and it shouldnt mean you just accept problems.

Hope this information is what you were looking for and possibly helps you with something to take to your dealer.

Thank you! I will have this addressed next dealer visit.

Luckyfd · March 1, 2020

On 2/12/2020 at 6:07 AM, Thomcat said:

Whole topic boils down to a "So what?"

It a piece of machinery operating with a number of temperature, mechanical and electronic input variables, plus a "self learning" feature that makes the whole system variable as a function of time and mileage. Not to mention an ever increasing number of multiple drum gearsets jammed into the same size case with one way and locking clutches to save mileage over its ancestors. Bands are constantly braking and releasing drumsets and depending upon the gear, multiple combinations have to occur simultaneously to get a smooth shiftpoint. So yeah, on an infrequent occasion a shiftpoint will screw up and you'll get a hard shift point or delayed downshift.....even a hang or two on the first 1-2 a sub freezing first upshift until fluid gets heated......so what?

Problem? Want a problem, then talk about a real problem like : no go situation, locked in 2nd limp in mode, band slippage, engine flaring, seal leakage, fluid burning, failure to upshift, metallic noises in the bell housing, etc......not an occasional hard shift point......I've a late build 8 speed with the Mobil1 HP and I occasionally get a hard shift point......again, so what, a quirk not a defect.

Want a really smooth tranny like my '74 Impala Custom? Toss out 2 drumsets to make a 4 speed, throw out all the EPA mileage crap like sprague clutches and locking torque convertors, install mechanical linkage connecting carb opening to tranny throttle, dump the electronics and install mechanical governors, and design the shiftpoints with a wicked gear overlap to mask drum set transfer.....and as long as the 454 was running smooth the tranny would shift smooth as silk first time, every time......and get a stinking 5-6 mpg on a good day!

Lol. I will always defend your right to say what you want. Not only is that my belief but my job for the last 24 years. I love your feisty passion. I do expect things I buy to do what they do without issue! When they don’t I expect the maker to fix this issue and I appreciate having a forum such as this one to find other people to help find solutions and information.