WELCOME TO RIVER DAVES PLACE

GM 8-Speed Transmission

Chili Palmer

Master of My Domian
Joined
Jan 7, 2010
Messages
8,766
Reaction score
13,808
I'm looking at getting back into a 1/2 ton truck after driving my 2500 HD for the last 10 years. The prices on new trucks is stupid, plus I haven't warmed up to the new GM styling or their utilitarian looking dash and uncomfortable interior, so I'm looking at 2018 1/2-ton GMC Denalis and happened to go online looking at reviews and a lot of follow up reviews were about the 8-speed trans that comes with the 6.2 engine. I've got that same trans in my CTS-V, but I only drive that on weekends, but it does have it's quirks, but nothing that makes it undriveable. The reviews said that it chatters, jerks, and is rough in its operation. I haven't experienced any of that in the Cadillac. Now if I drove it on an everyday basis it might present itself, but after reading about the issues on this trans it makes me want to maybe hang on to my current ride.

Anyone experienced any of these issues with your GM truck or SUV?
 

white tortilla

Well-Known Member
Joined
May 10, 2010
Messages
1,111
Reaction score
1,306
My 2015 Chevy 1500 6.2 with the 8 speed has chattered & jerked since about 40k miles. I’m at 160 now it just gets worse but keeps running.
 

SFV2RVR

Registered Parker Legend
Joined
Oct 4, 2007
Messages
2,772
Reaction score
1,730
I'm looking at getting back into a 1/2 ton truck after driving my 2500 HD for the last 10 years. The prices on new trucks is stupid, plus I haven't warmed up to the new GM styling or their utilitarian looking dash and uncomfortable interior, so I'm looking at 2018 1/2-ton GMC Denalis and happened to go online looking at reviews and a lot of follow up reviews were about the 8-speed trans that comes with the 6.2 engine. I've got that same trans in my CTS-V, but I only drive that on weekends, but it does have it's quirks, but nothing that makes it undriveable. The reviews said that it chatters, jerks, and is rough in its operation. I haven't experienced any of that in the Cadillac. Now if I drove it on an everyday basis it might present itself, but after reading about the issues on this trans it makes me want to maybe hang on to my current ride.

Anyone experienced any of these issues with your GM truck or SUV?

I had a 2017 Sierra Denali with a Magnusson tvs2300 blower and kooks long tubes and a custom tune done and also had the 8 speed tuned with the A8 shift points. Ran the truck for 100k miles with this tuneup making 525Wrhp with zero issues!


Sent from my iPhone using Tapatalk
 

LargeOrangeFont

Moderation Enthusiast
Staff member
Joined
Sep 4, 2015
Messages
32,250
Reaction score
45,973
I had a 2017 Sierra Denali with a Magnusson tvs2300 blower and kooks long tubes and a custom tune done and also had the 8 speed tuned with the A8 shift points. Ran the truck for 100k miles with this tuneup making 525Wrhp with zero issues!

Your trans tune fixed the trans issues most experience with a stock truck.
 

Chili Palmer

Master of My Domian
Joined
Jan 7, 2010
Messages
8,766
Reaction score
13,808
I had a 2017 Sierra Denali with a Magnusson tvs2300 blower and kooks long tubes and a custom tune done and also had the 8 speed tuned with the A8 shift points. Ran the truck for 100k miles with this tuneup making 525Wrhp with zero issues!


Sent from my iPhone using Tapatalk
What did it run you to do all that work to your truck? Did you do it or have done?
 

SFV2RVR

Registered Parker Legend
Joined
Oct 4, 2007
Messages
2,772
Reaction score
1,730
What did it run you to do all that work to your truck? Did you do it or have done?

About 12k installed. Had a shop Powerhouse Performance in Simi Valley, Ca do the install. They did my Whipple on my Escalade as well.


Sent from my iPhone using Tapatalk
 

Runs2rch

Well-Known Member
Joined
Jun 10, 2013
Messages
7,679
Reaction score
5,996
I have a 2017 Silverado 6.2 8 speed. No issues. All the 8 speed issues seem to be prevalent in the Colorado 8l45. The 8l90 has some I'm sure, but what manufacturer puts out a vehicle with zero issues.
 

79howard

Well-Known Member
Joined
Oct 14, 2016
Messages
48
Reaction score
54
We have a 2016 GMC Yukon XL Denali with 75k on the clock. Does some wonky shifts but no shudders. Did the dealers fix where they flush and replace with Mobil 1 full synthetic. No change. My mom has a Cadillac CTS with Same trans. She has 36ish on the clock and was experiencing the shudder. Did the dealer flush and fluid swap with Mobil 1 and the shudders gone.


Sent from my iPhone using Tapatalk
 

wishiknew

Well-Known Member
Joined
Dec 19, 2007
Messages
5,024
Reaction score
1,777
You will want a 2500 as soon as you get a 1500 have a 2017 with 100K 6.2 8 speed have not had 3rd gear since 40K truck hauls ass but don’t like towing stuff and no one can rework the trans but Chevy dealer because of program in computer
 

BajaMike

Well-Known Member
Joined
Sep 20, 2007
Messages
6,192
Reaction score
2,761
I don’t trust the 8 speed tranny for regular or heavy duty use. Chev did it when they went away from the 4.10 rear end. 8 speed tranny on a Honda, fine. A 2500 HD, no thanks. Until they perfect them and beef them up.
 

Runs2rch

Well-Known Member
Joined
Jun 10, 2013
Messages
7,679
Reaction score
5,996
I don’t trust the 8 speed tranny for regular or heavy duty use. Chev did it when they went away from the 4.10 rear end. 8 speed tranny on a Honda, fine. A 2500 HD, no thanks. Until they perfect them and beef them up.

Why post an uneducated opinion?

The 8L90 can handle 800-900rwhp. Much stronger than the 4l80e in your old 2500.

They are plenty strong.
 

wishiknew

Well-Known Member
Joined
Dec 19, 2007
Messages
5,024
Reaction score
1,777
Why post an uneducated opinion?

The 8L90 can handle 800-900rwhp. Much stronger than the 4l80e in your old 2500.

They are plenty strong.
Mine has 420 hp and no 3rd gear no to strong for that ?
 

SOCALCRICKETT

Well-Known Member
Joined
Dec 22, 2008
Messages
2,927
Reaction score
3,964
I have a 2019 half ton with the 8l90, and yes it is a funky trans. It sometimes has a delay on a reverse to neutral to 1st, the 2nd to 3rd and be rough shift as well. Other than that in 20k I haven't had any issues. I do tow the formula with it and I'm tipping the scales at 9k on trailer. In all honesty I would rather have the 6l80 that my last 2500 had instead but the 8l90 has never let me down, the 6l80 was much smoother and seems more refined

Sent from my SM-G981U using Tapatalk
 

rivrrts429

Arch Stanton...
Joined
Jan 4, 2008
Messages
16,996
Reaction score
28,693
I have a 2019 and it’s been in the shop three times for the trans. Each time it’s fine for a month or two then goes back to its antics.

The shift from 1st to 2nd will give you whiplash randomly. Then it flares randomly from 30-40mph.

I hate this truck
 

wishiknew

Well-Known Member
Joined
Dec 19, 2007
Messages
5,024
Reaction score
1,777
I had 2 trucks with Allison trans never a problem with them
 

BajaMike

Well-Known Member
Joined
Sep 20, 2007
Messages
6,192
Reaction score
2,761
Why post an uneducated opinion?

The 8L90 can handle 800-900rwhp. Much stronger than the 4l80e in your old 2500.

They are plenty strong.

Yes, I’m “uneducated”. My 2500 HD Crew has got 190,000 miles on the 6.0 and “3 speed plus OD” tranny, not a single hiccup. And I know nothing about the 90 fleet trucks and ambulances and 3 airplanes I’ve owned.
 

hboutlaw

Active Member
Joined
Aug 22, 2014
Messages
29
Reaction score
21
I have a 2019 and it’s been in the shop three times for the trans. Each time it’s fine for a month or two then goes back to its antics.

The shift from 1st to 2nd will give you whiplash randomly. Then it flares randomly from 30-40mph.

I hate this truck
I have a 2018 GMC Sierra 1500 with the same problem. Had transmission fluid changed as recommended and that fixed some of the problems. Had SW updated and that fixed some other problems. All in all this remains a POS transmission. Join the class action lawsuit.
The key is to drive the piss out of it and that seems to avoid the erratic behavior...for the most part.
 

rivrrts429

Arch Stanton...
Joined
Jan 4, 2008
Messages
16,996
Reaction score
28,693
I have a 2018 GMC Sierra 1500 with the same problem. Had transmission fluid changed as recommended and that fixed some of the problems. Had SW updated and that fixed some other problems. All in all this remains a POS transmission. Join the class action lawsuit.
The key is to drive the piss out of it and that seems to avoid the erratic behavior...for the most part.



It’s weird you say that about driving the piss out of it. It actually seems to help. I drive it like it’s a rental car and it does better for a longer period of time.

I just hate being that douchebag that mashes the pedal everywhere I go lol
 

Gelcoater

Well-Known Member
Joined
Sep 26, 2009
Messages
18,706
Reaction score
24,853
I have a 2018 GMC Sierra 1500 with the same problem. Had transmission fluid changed as recommended and that fixed some of the problems. Had SW updated and that fixed some other problems. All in all this remains a POS transmission. Join the class action lawsuit.
The key is to drive the piss out of it and that seems to avoid the erratic behavior...for the most part.
This is interesting.
Now, bear with me here. My 15 year old Dodge will, on occasion start shifting weird. Can’t decide on 3rd or overdrive. And I found if I mash it it seems to shift fine.
With some online research I tracked it to a poor ground connection.
Replaced the loose fitting old ground cables with tight fitting new ones and the problem goes away.
Could it be?
Maybe check your grounds?
 

BajaMike

Well-Known Member
Joined
Sep 20, 2007
Messages
6,192
Reaction score
2,761
This is interesting.
Now, bear with me here. My 15 year old Dodge will, on occasion start shifting weird. Can’t decide on 3rd or overdrive. And I found if I mash it it seems to shift fine.
With some online research I tracked it to a poor ground connection.
Replaced the loose fitting old ground cables with tight fitting new ones and the problem goes away.
Could it be?
Maybe check your grounds?

Thats interesting. I had ‘99 Chev1500, did weird stuff, thought it was the ignition computer, ended up it was a loose ground wire.
 

bk2drvr

Well-Known Member
Joined
Jul 9, 2015
Messages
1,134
Reaction score
1,202
When I was buying my 2018 Sierra I wanted the 8 speed trans and everything I was reading was scaring the shit out of me so I said forget it. I ended up getting the 6 speed thinking it was two additional speeds than my 2001 Silverado so I felt I was ahead of the game. No regrets it’s been an awesome truck. At the time the 8 speed issues weren’t fixable, not sure what the situation is today. It’s a crap shoot. Good luck.
 

CobraDave

Well-Known Member
Joined
May 20, 2013
Messages
3,166
Reaction score
2,784
I just saw a new Yukon fully on fire on the freeway. May not help with a decision, or will it?


Sent from my iPhone using Tapatalk
 

OldSchoolBoats

No longer "boatless".......
Joined
May 8, 2014
Messages
14,277
Reaction score
18,352
I have a 2019 and it’s been in the shop three times for the trans. Each time it’s fine for a month or two then goes back to its antics.

The shift from 1st to 2nd will give you whiplash randomly. Then it flares randomly from 30-40mph.

I hate this truck
Your comments on your 1500 probably saved me a bunch of headaches. I was ready to go on the Chevy, but you talked me out of it.

First On Race Day for life!!

Sent from my SM-N960U using Tapatalk
 

Runs2rch

Well-Known Member
Joined
Jun 10, 2013
Messages
7,679
Reaction score
5,996
Yes, I’m “uneducated”. My 2500 HD Crew has got 190,000 miles on the 6.0 and “3 speed plus OD” tranny, not a single hiccup. And I know nothing about the 90 fleet trucks and ambulances and 3 airplanes I’ve owned.
Everyone is uneducated about something. I was implying your post was uneducated. Not you.

Your 6.0 has a 4l80e behind it. Great transmission. Are they perfect no.

All of these modern transmissions have problems. The 10 speed that Ford and GM share isn't perfect. If you go on the internet you read from the 1-3 percent that have issues. Go on a Raptor Forum and there is plenty. Is the Raptor a bad truck? No.

3.5 Ecoboost. Good engine. If you go on the internet Cam phasers and waste gate rattles will be the main topic.

Everything has inherent issues. Just the way it is.
 

BajaMike

Well-Known Member
Joined
Sep 20, 2007
Messages
6,192
Reaction score
2,761
Everyone is uneducated about something. I was implying your post was uneducated. Not you.

Your 6.0 has a 4l80e behind it. Great transmission. Are they perfect no.

All of these modern transmissions have problems. The 10 speed that Ford and GM share isn't perfect. If you go on the internet you read from the 1-3 percent that have issues. Go on a Raptor Forum and there is plenty. Is the Raptor a bad truck? No.

3.5 Ecoboost. Good engine. If you go on the internet Cam phasers and waste gate rattles will be the main topic.

Everything has inherent issues. Just the way it is.

1-3% “have issues”. That’s a pretty good number, except if you are in the 1-3%. We can make good multi-speed transmissions, been doing it for agriculture tractors and commercial trucks for years. Making inexpensive ones for consumer trucks is a different ball game.
 

Runs2rch

Well-Known Member
Joined
Jun 10, 2013
Messages
7,679
Reaction score
5,996
1-3% “have issues”. That’s a pretty good number, except if you are in the 1-3%. We can make good multi-speed transmissions, been doing it for agriculture tractors and commercial trucks for years. Making inexpensive ones for consumer trucks is a different ball game.
Agree.
 

poncho

Well-Known Member
Joined
Dec 20, 2007
Messages
3,632
Reaction score
3,526
2018 Sierra Denali, sometimes when it's cold the 2nd to 3rd gear shift feels soft otherwise zero issues, 14,000 miles....Love the truck and how it drives.
 

HBCraig

Well-Known Member
Joined
Jan 8, 2008
Messages
6,408
Reaction score
5,040
I was told by a few buddies to go with the 10 speed and the 8 speed sucks but they didn't say why. I say go for it.
 
Joined
Jun 15, 2016
Messages
23
Reaction score
42
I have a 2015 Silverado with a 6.2 and a 8 speed transmission that I bought from a member with 60,000 miles and that now has 130,000 miles. It does shift hard maybe once or twice a month but then goes back to shifting normal again. I am willing to put up with crazy shifting every once and a while because the truck is a blast to drive.
 

76 Hondo

76 Hondo
Joined
Dec 22, 2007
Messages
1,683
Reaction score
1,555
When I was buying my 2018 Sierra I wanted the 8 speed trans and everything I was reading was scaring the shit out of me so I said forget it. I ended up getting the 6 speed thinking it was two additional speeds than my 2001 Silverado so I felt I was ahead of the game. No regrets it’s been an awesome truck. At the time the 8 speed issues weren’t fixable, not sure what the situation is today. It’s a crap shoot. Good luck.
Just had to put a transmission in my 2017 Sierra, 5.3 with 6 speed, 73,000 miles, serviced at 40,000? 2005 5.3 with 4 speed went over 225,000 before rebuild! Maybe they average out.
 

DogNamedChevy

Motor Boating
Joined
Dec 20, 2007
Messages
645
Reaction score
250
Just had to put a transmission in my 2017 Sierra, 5.3 with 6 speed, 73,000 miles, serviced at 40,000? 2005 5.3 with 4 speed went over 225,000 before rebuild! Maybe they average out.
Damn! I guess I should be happy my 2016 Silverado 5.3 with the 6 speed made it 93,000 miles [emoji2959]

Sent from my SM-G975U using Tapatalk
 

HALLETT BOY

Well-Known Member
Joined
Oct 12, 2007
Messages
5,163
Reaction score
5,533
I bought a Ram because of the ZF 8 speed , after 55K miles , it’s been amazing. I pull 7500 lbs on occasion.
 

Runs2rch

Well-Known Member
Joined
Jun 10, 2013
Messages
7,679
Reaction score
5,996
I bought a Ram because of the ZF 8 speed , after 55K miles , it’s been amazing. I pull 7500 lbs on occasion.
I drove a new Ram 1500 last Saturday. The ZF 8 speed felt fine. I was expecting to be wowed from all the forum reading. 3.92's limited slip. Standard non etorque Hemi.

What trim is yours?
 

HALLETT BOY

Well-Known Member
Joined
Oct 12, 2007
Messages
5,163
Reaction score
5,533
I drove a new Ram 1500 last Saturday. The ZF 8 speed felt fine. I was expecting to be wowed from all the forum reading. 3.92's limited slip. Standard non etorque Hemi.

What trim is yours?
Lariat , with factory air suspension, amazing . Also 3.92 , LSD .
 
Top