Poll: How has your 8-speed been for you?

CadillacLuke24 · February 16, 2019

On 2/5/2019 at 8:26 AM, qwank said:

Here's the new fluid bottles

Is the Mobil Part number 124715? No dice at any dealers yet, but Summit and other sites are starting to list it, and it's the blue label bottle. I know, same color means same stuff, but I like the certainty of parts numbers.

qwank · February 16, 2019

6 hours ago, CadillacLuke24 said:

Is the Mobil Part number 124715? No dice at any dealers yet, but Summit and other sites are starting to list it, and it's the blue label bottle. I know, same color means same stuff, but I like the certainty of parts numbers.

I'm not sure what the Mobil part number is, we only use the 8 digit GM numbers at work. h

CadillacLuke24 · February 17, 2019

Nuts! At any rate the Summit stuff is blue label, so I have no problem picking some up.

Thank you again qwank! You are the man!

Now to find the trans cooler line out of the trans...that will make my fluid swap more thorough AND cleaner!

qwank · February 21, 2019

On 2/16/2019 at 3:14 AM, CadillacLuke24 said:

Is the Mobil Part number 124715? No dice at any dealers yet, but Summit and other sites are starting to list it, and it's the blue label bottle. I know, same color means same stuff, but I like the certainty of parts numbers.

Hyde Country · February 23, 2019

Hey guys first post. This topic is what lead me to the forum. I have a 2018 High Country 6.2L with 22” wheels. I had really bad low speed shutter at 3000 miles. Dealer did flush. Fixed low speed shutter but transmission still clunks, bangs, gets truipped up or confused and sometimes feels like it lurches slightly after accelerating and then stopping at a red light. Have to say been so disappointed ☹️. I have about 7k on truck now. Gonna take it in and tell them to drive it. Part of the problem may be the z60 suspension from what I have read here as well. It handles great but the ride feels like a board on the highway. Sometimes I wonder if the crappy ride is tranny related? Thought about taking off the 22” wheels. It was my first time to go to a dealership and leave with the one I wanted with the intent for it to be a long term truck. Now I’m wishing I would have waited for the 19. It has taken away the satisfaction from driving my truck. I should be saying “damn this is a bad ass truck” every time I drive it, instead of wating on the next something clunk. I’m just concerned if it’s doing this now, will it last?

CadillacLuke24 · February 23, 2019

On 2/21/2019 at 12:13 PM, qwank said:

You DA MAN, MAN! Thank you qwank! Two cases on order

CadillacLuke24 · February 23, 2019

4 hours ago, Hyde Country said:

Hey guys first post. This topic is what lead me to the forum. I have a 2018 High Country 6.2L with 22” wheels. I had really bad low speed shutter at 3000 miles. Dealer did flush. Fixed low speed shutter but transmission still clunks, bangs, gets truipped up or confused and sometimes feels like it lurches slightly after accelerating and then stopping at a red light. Have to say been so disappointed ☹️. I have about 7k on truck now. Gonna take it in and tell them to drive it. Part of the problem may be the z60 suspension from what I have read here as well. It handles great but the ride feels like a board on the highway. Sometimes I wonder if the crappy ride is tranny related? Thought about taking off the 22” wheels. It was my first time to go to a dealership and leave with the one I wanted with the intent for it to be a long term truck. Now I’m wishing I would have waited for the 19. It has taken away the satisfaction from driving my truck. I should be saying “damn this is a bad ass truck” every time I drive it, instead of wating on the next something clunk. I’m just concerned if it’s doing this now, will it last?

I believe the Z60 is the regular suspension, should be relatively soft. The primary source of your concern unfortunately will be the 22s, with that much wheel there just isn't much sidewall to absorb bumps, so you feel them more.

Sorry to hear your transmission isn's shifting right. Have you returned to the dealer recently?

CCI777 · March 5, 2019

Hi Guys, first post. I have a 2017 High Country and have been experiencing a hard shift from 1st to 2nd gear, but it only does it in the morning for the first 3 take offs from a dead stop, then it goes away. I have about 28k miles and it started about 14k miles. The first time I took it to the dealer, they said they had to do a "re-learn", one of the tech's had to drive it home for the weekend and drive it on the highway early morning at a certain constant speed for a few miles. Well I picked it up the next morning and it didn't fix the problem.

I took it back a couple weeks later and this time they "re-programmed" the transmission and said it was fixed. I picked it up and drove it a couple days, and still no change.

I took it back again and they flushed it out and put the new fluid in it, still didn't fix the problem.

They ended up replacing the transmission under warranty, so it drives much better, I still think this 8 speed transmission might have problems down the road. It's a shame, because I really love this truck.

L86 All Terrain · March 6, 2019

Mine got the TC recall before I picked up the truck, OEM 8L90e started delayed reverse engagement at 30,000km after 2yr. They replaced the trans with a reman unit. Shifts great, even better than the original but for some reason it seems to hold a gear slightly longer, and not kick into AFM as often as before. Perhaps the new trans had a updated tune? Truck is put away for winter, hope to be back in it come mid-April. Might sell it and buy a C6 Z06, I have enough trucks to drive I don't need a show pony to sit in a garage, I might as well have a sports car for that.

Denny · March 13, 2019

I have a 2018 Dinali eight speed transmission while going down a hill with cruise on or off the tachometer constantly jumps between 1000 RPMs and 1500 RPMs and sometimes between 1500 RPMs and 2000 RPMs . It’s while driving at 40 miles an hour or above it’s like the transmission cannot make up its mind which gear to go in. The tachometer will Bob up-and-down about once per second until I get at the base of the hill and it is always with no load on the motor that is coasting . The dealer could find nothing wrong with the transmission or any components they change the transmission fluid but the problem still persists

Hillwood · March 30, 2019

On 2/17/2019 at 1:29 AM, CadillacLuke24 said:

Nuts! At any rate the Summit stuff is blue label, so I have no problem picking some up.

Thank you again qwank! You are the man!

Now to find the trans cooler line out of the trans...that will make my fluid swap more thorough AND cleaner!

What are you using to bypass the thermal valve for flushing?

CadillacLuke24 · March 31, 2019

Haven't got that far yet, it's my understanding that the trans pump will evacuate the pan.

Considering what you just mentioned, I bet I can perform the drain when the engine has reached operating temperature, that way the valve should be open.

Hillwood · March 31, 2019

The thermal bypass valve doesn't open until the transmission fluid reaches 194 degrees. That's when it allows fluid to flow through the cooler.

Under that temperature, the valve is closed.

There is supposed to be a service tool to put in place of the valve for flushing through the cooler lines.

I haven't seen the tool yet.

CadillacLuke24 · June 22, 2019

I disconnected the cooler lines where they come off the transmission. That worked fairly well, other than it pissed transmission fluid EVERYWHERE because I didn't get the lines clear of the fluid stream, and it seemed to clear the pan and not much else. I think next time I will just do a pan drop, and maybe use a pump to try and evacuate the cooler lines.