8 speed Transmission cold slip

OUTLANDER XT · March 23, 2021

Hey guys and gals,

new here, hoping I can get some answers as I'm not buying what the dealer is telling me. I have a 2019 GMC Elevation, with a 5.3 and an 8 speed tranny. Truck has 19,000 on it. When the truck sits for a couple days, and you start it and put it in gear imediatly it starts to move but when you give it throttle, it slips like the truck is on ice. If you drive it everyday, it doesn't do it. It's almost like the torque converter is bleeding down. If you start it and let it warm up for 5 sec it is fine. I've had many vehicles over the years but have never encountered this. The dealer claims that this is normal, but not really sure I believe this. Anyone else run into this? KB

ftwhite · March 23, 2021

My 2018 8speed, does this almost every morning shifting from 1-2 when cold unless I either 'gun it', or sometimes warmup a really long time (5-10min). There is doc that GM pointed me to (16-NA-361). I'll try to find it, but it will be different for 2019 I assume. It was explained to me that the fluid pressure needed to build up.

Earl Cordova · March 23, 2021

My 05 2500 has done it since I purchased it in 2012.

I have had it checked by the dealer when it is in for annual maintenance more times that I can count.

They can never find anything wrong with it, and act like I am idiot that doesn't know anything about how a transmission should work.

I also own a 01 2500 and it has never done it.

mbaee · March 23, 2021

1 hour ago, OUTLANDER XT said:

Hey guys and gals,

new here, hoping I can get some answers as I'm not buying what the dealer is telling me. I have a 2019 GMC Elevation, with a 5.3 and an 8 speed tranny. Truck has 19,000 on it. When the truck sits for a couple days, and you start it and put it in gear imediatly it starts to move but when you give it throttle, it slips like the truck is on ice. If you drive it everyday, it doesn't do it. It's almost like the torque converter is bleeding down. If you start it and let it warm up for 5 sec it is fine. I've had many vehicles over the years but have never encountered this. The dealer claims that this is normal, but not really sure I believe this. Anyone else run into this? KB

My 2019 LT is the same way. Recently had it in the shop for similar issues:

- Harder 1-2 and 2-1 shifts compared to other shifts since day one (rougher on cold mornings). I was told it was normal by the service dept and all GM 8 speeds do it.

- Occasional slips from first to second gear when warmed up after coming from reverse like pulling out of a parking spot. When it re-engages, it kicks so hard it feels like I was rear-ended.

- Mechanical linkage sound (sounds like a manual transmission shifting) when dropping into first after coasting/lightly braking to a stop while warmed up. Doesn't do it if I stop normally but I try to coast approaching a red light and roll through the green.

- Slipped while climbing out of an underground parking garage. Fairly steep exit ramp and it slipped for a second on the way up.

They reprogrammed the TCU and took it for a long test drive. "Unable to duplicate", "Working normally" and "Mechanically perfect" are the phrases the service writer used when I picked it up. I'd like to know how they can say "Mechanically perfect" if they didn't tear it down on the bench. Of course the reprogram didn't solve anything.

Earl Cordova · March 23, 2021

9 minutes ago, mbaee said:

....... "Unable to duplicate", "Working normally" and "Mechanically perfect" are the phrases the service writer used when I picked it up. I'd like to know how they can say "Mechanically perfect" if they didn't tear it down on the bench.

I have heard the same thing numerous times. I started having them change the filter and oil every year in the hopes I get a mechanic that really knows what he is doing.

Two or three years ago I had some extra cash laying around due to an unexpected bonus and asked them to put in a factory rebuilt transmission since I rely on this truck when way out in the desert. They dealer would not do it since nothing was wrong.

redwngr · March 23, 2021

Apparently, some delay is considered normal for a 'garage shift'.

There is a 'delayed engagement' test to see if it meets the 'normal' criteria.

(or let it run or a few seconds after starting...)

https://gm-techlink.com/?p=13727

Delayed Transmission Engagement

September 30, 2020

Some 2018-2019 ATS, CTS, CT6, Corvette; 2018-2020 Express; 2018-2021 Camaro, Colorado, Silverado, Canyon, Savana, Sierra; and 2021 CT4 models equipped with the 8L45 or 8L90 8-speed automatic transmission (RPO M5T, M5N, M5U, M5X, MQD, MQE) may have a delayed engagement condition when the transmission is shifted from Park to Reverse or Park to Drive after the vehicle has been sitting with the engine off. (Fig. 12) The delayed engagement typically occurs after several hours or, more commonly, overnight.

Fig. 12

The condition may seem to be delayed gear engagement, a slipping transmission, or delayed engagement followed by a harsh engagement.

The transmission is designed to allow three seconds to complete a garage shift (shifting from Park to Reverse or Park to Drive). If the engine speed is increased before the transmission has engaged, the garage shift may be harsh.

After the initial shift, transmission operation will be normal for the subsequent engagements. The condition will not occur again until the vehicle sits again with the engine off for several hours or overnight.

Delayed Engagement Test

Use GDS2 to monitor engine RPM and the transmission input speed sensor (ISS) prior to starting the engine. Start the engine with the transmission in Park and shift the vehicle from Park to Drive or Park to Reverse with the service brake applied. The ISS should drop to zero within three seconds, which is the clutch engagement time. Recording the GDS session log can be useful in diagnosing the condition.

Delayed engagement of Park to Reverse or Park to Drive is present if the time difference between the gear selected (Pt. 1) and the transmission input shaft speed reaching 0 RPMs (Pt. 2) exceeds three seconds. (Fig 13)

Fig. 13

In most cases, the transmission will engage in three seconds or less, which is considered an acceptable engagement time and no repairs should be attempted.

TIP: The vehicle should only be evaluated after sitting for a minimum of eight hours but less than 24 hours and at an ambient temperature of 50°F (10°C) or above.

If engagement time exceeds three seconds, attempt to learn the C3 – Drive and C5 Reverse – Clutch using the following steps:

Allow the transmission sump temperature to rise between 20° and 30°C (68° and 86°F). Do not apply the accelerator pedal.
Perform 20 Park to Reverse shifts or 20 Park to Drive shifts releasing the brake pedal with each shift, allowing the vehicle to roll 5-10 feet (1.5-3.0 m) per engagement into gear.

If the learn procedure does not correct the condition, disassemble the transmission and inspect the 1-3-5-6-7 Clutch (C3) for a delay into Drive condition and inspect the 4-5-6-7-8 Reverse Clutch (C5) for a delay into Reverse condition. The respective clutch plates and seals should be inspected for wear and or damage and repaired accordingly.

If the vehicle has less than 2,500 miles (4,000 km), the transmission or valve body has been replaced or a clutch repair has been performed, follow the clutch learn procedure in Bulletin #16-NA-019 to learn the C5 Reverse and C3 Drive Clutch.

For additional information on a delayed transmission engagement condition, refer to Bulletin #20-NA-187.

OUTLANDER XT · March 24, 2021

Thanks for the info. Still seems odd to me that they would design it as such.

Silverado4x4 · March 24, 2021

On 3/22/2021 at 8:35 PM, OUTLANDER XT said:

Hey guys and gals,

new here, hoping I can get some answers as I'm not buying what the dealer is telling me. I have a 2019 GMC Elevation, with a 5.3 and an 8 speed tranny. Truck has 19,000 on it. When the truck sits for a couple days, and you start it and put it in gear imediatly it starts to move but when you give it throttle, it slips like the truck is on ice. If you drive it everyday, it doesn't do it. It's almost like the torque converter is bleeding down. If you start it and let it warm up for 5 sec it is fine. I've had many vehicles over the years but have never encountered this. The dealer claims that this is normal, but not really sure I believe this. Anyone else run into this? KB

No transmission likes what your doing on a cold start up especially sitting for 2 days. Your starting up immediately putting it into gear it hasn't built pressure yet and its going to slip.

Edited March 24, 2021 by Silverado4x4

bigdoug42 · April 3, 2021

I always let the truck run for 3-5 minutes from cold start to let fluids build up, and when I go from R to D, I'll let it sit in N for like 5 sec. If traffic will let me.

Also had the trans flushed and new synthetic Mobil 1 fluid put in for ATCC shudder. Trans works like it should, just gotta let the trans software load, I guess.

JohnVec · October 2, 2022

My 2021 GMC Sierra 1500 2.7L turbo has what seems to be a slip between first and second gear only in the morning when first shifts take place. Only does it once. The rest of the day it’s fine. I’m concerned and dealer says it’s normal. I don’t agree.

2016 Sierra Owner · October 3, 2022

7 hours ago, JohnVec said:

My 2021 GMC Sierra 1500 2.7L turbo has what seems to be a slip between first and second gear only in the morning when first shifts take place. Only does it once. The rest of the day it’s fine. I’m concerned and dealer says it’s normal. I don’t agree.

You don't have to agree. However just about every 8 speed owner that comes here complaining about the transmission has the same issues you are describing. GM has a few "fixes" they can try some work some don't. This is a known issue since GM started putting these transmissions in their trucks around 2016/2017. Also there are a few class action lawsuits over the problems but, I don't think those have gotten anywhere.

voided3 · October 3, 2022

Our '21 Silverado 5.3 8-speed hasn't done the cold 1-2 rough shift in a while, but it has multiple times before. I got in the habit of holding it in neutral for a few seconds between reverse and drive, and that seems to prevent it.

I also always let it warm up for a minute or two before leaving (until the tachometer goes down to a normal idle speed, around 600 RPM). This warm up procedure is generally a good practice for any vehicle on a cold start, really.

Gangly · October 3, 2022

JohnVec

The quick/abrupt 1-2 shift right after startup is normal for the 6 spd transmissions and there is a bulletin out about it. If the abrupt 1-2 shift happens after the first or second set of shifts in the morning, then its an issue that needs to be addressed.

For the 6 spd.:

When transmission ATF temperature is at or below 85 degrees F (30 degrees C).
This 2-3 upshift flare can occur until the ATF temperature warms.

If the 2-3 flare is determined to be ATF temperature sensitive use a Tech 2 or GDS2 to make note of the throttle position when the flare occurs

Drive the vehicle to get ATF temperature to at least 104 degrees F (40 degrees C) and then make several 2-3 shifts at the throttle position determined to be the most sensitive to the 2-3 flare.

This will allow the transmission adapts to tailor the shifts and may help to eliminate the cold 2-3 flare.

This condition is a NORMAL characteristic of the transmission, it will not cause durability concerns and no repair attempts should be made.

Please share this information with the customer, including a copy of this message.

Being an 8 spd, I dont know if this information helps you at all, but it might be relative since the symptoms sound very similar. Best to take it to a dealership and let them sort it out if you can. On a side not, my 2020 5.3 with the 8 spd does the same exact thing and has since day 1

Edited October 4, 2022 by Gangly

pokismoki · October 16, 2022

have you tried doing a trans reset, and re-learn to see if it clears any issues?

there is also trans purge and trans clean function , they might help blow out any hiccups

Edited October 16, 2022 by pokismoki

elcamino · October 17, 2022

GM has a bad history with low bidder ATF that last 10 yrs or so. I would replace the OEM ATF wannabe synthetic with a PAO synthetic asap and not use anything GM recommends. Get the best available that is not associated with GM as they only care about the truck lasting the warranty, after that its YOUR PROBLEM.

Edited October 17, 2022 by elcamino