Transmission Slipping? Anyone having similar issues

JSW74 · May 14, 2020

Truck is a 2019 Silverado 1500 Z71 crew cab with the 5.3L. When shifting back into drive from reverse the transmission "slips" and when it catches it slams into gear. It does not happen every time but is a severe annoyance especially for a truck with only 6500 miles on it. A 2 inch level was just added but it did it before. Other than the level its a stock truck.

AdamAT4 · May 14, 2020

Sounds like a Chrysler transmission was put in your truck by mistake, many of them slip in reverse.

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ejdziurka · May 14, 2020

First shift of the day only? I'm no transmission guy, but I've read enough on here that is has to do with the fluid thickness, availability, and what clutch pack it can get to when shifting for the first time. Only any combination of those three. You will notice it more in the winter when the fluid is really cold. I'll even go as far as to say I've read it may slip by design to build heat up in the transmission to free the fluid up.

JSW74 · May 14, 2020

35 minutes ago, ejdziurka said:

First shift of the day only? I'm no transmission guy, but I've read enough on here that is has to do with the fluid thickness, availability, and what clutch pack it can get to when shifting for the first time. Only any combination of those three. You will notice it more in the winter when the fluid is really cold. I'll even go as far as to say I've read it may slip by design to build heat up in the transmission to free the fluid up.

To me it definitely seems to happen more when the trucks been running a bit, so when the fluid is hotter. I checked the fluid temp per the dash read out when it happened yesterday and it was at 175 degrees. The wife drove the truck today and it did it as she went to take off from a stop sign, truck was in drive the entire time. Dropping the truck off tomorrow at the dealership for it to be looked at. I will try and keep yall posted

bamorris2 · May 14, 2020

I also have a 2019 with the 8 speed, and it’s happened to me a few times. It slams hard when it does. I found it happens when I transition from reverse to drive without giving it enough time to fully engage drive. If I give it a moment then it’s fine. Problem is, sometimes parking maneuvers or multi-point u-turns need quick shifts from reverse to drive, which is usually when this bites me.

Thomcat · May 14, 2020

The first overnight cold engagement is usually just on the first one or two 1-2 upshifts of the day. Sounds more like a delayed engagement than slippage......slippage will cause an engine flare/and/or stuttering before engagement.

Food for thought - I'm guessing an 8 speed with start-stop. Happen after an auto stop event? The '19s differ from the previous 8 speeds in that they have an "accumulator" a cylinder that stores hydraulic pressure when the engine and hydraulic pump in the tranny are stopped. This pressure is needed to supply the servos to keep the bands against the drums of the gearsets, otherwise absent pressure the bands will release and reapply as soon as the engine and tranny pump resume operation and apply hydraulic pressure. If the accumulator fails to apply sufficient pressure during an auto stop cycle, the bands will slam against and engage the drum(s) as soon as the engine revs and powers the tranny pump.....higher the rev, the harder the slam.

Dealer will probably do a fluid change (if date on the door sticker is earlier than 3/19 when they switched to factory Mobil1 tranny fluid), and/or otherwise reprogram the tranny computer. Bear in mind this can also occur in a normal tranny with multiple drivers with drastically different driving habits, i.e. slow vs. jackrabbit takeoffs, because one of the attributes of the self learning tranny is it modifies the fill rates of the hydraulic servos which will affect the speed of band engagement.

I've read that the 20+ trannys dumped the accumulator in favor of an electric hydraulic pump in the tranny which operated independently of the engine to keep pressure during an auto stop cycle. Let's see what the dealer says.

jlong1984 · May 14, 2020

Happens to me like clockwork on the first 1-2 shift of the day after backing out of my driveway, after that, smooth as butter.

BlancoSilverado · May 14, 2020

Same happens to me on my 8L90. When i park on the street (after driving home from work) and have to pop into my neighbors driveway to turn around. Goes into reverse fine, then go into the street switch to drive and BOOM. Sounds like it slams into second then switches to first. If i wait for 2 full seconds it doesnt do it.

JSW74 · May 15, 2020

I appreciate yalls input I’m dropping it off in the morning to see what the dealership has to say. Definitely not something I expected to deal with especially with a brand new truck and only 6500 miles. The wife is more pissed off about it than me.

Thomcat · May 15, 2020

2 hours ago, BlancoSilverado said:

Same happens to me on my 8L90. When i park on the street (after driving home from work) and have to pop into my neighbors driveway to turn around. Goes into reverse fine, then go into the street switch to drive and BOOM. Sounds like it slams into second then switches to first. If i wait for 2 full seconds it doesnt do it.

Same as mine.....my guess is that the accumulator bleeds down overnight and it after inital startup and shifting it takes a few seconds for the accumulator to refill, especially when cold and the fluid thickens, and supply proper pressures for shifting. Once and done and then smooth shifting the rest of the day. An occasional slam.....can't damage anything........we're too spoiled, old 60-70s era 2 speed Powerglides did it on every 1-2 shift

GMCustomerService · May 22, 2020

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