8 speed longevity

[Ranger522vx]

I need someone to make me feel better about my 2019 trail boss purchase.  
 

I traded my 2015 sierra Denali 6.2 8 speed in on the 5.3 8 speed trail boss.  The Sierra had the transmission replaced under warranty at 30,000 miles.  It still clunked around but not as bad and had other problems which led me to trade.  Now I have the trail boss 8 speed and although it is better it still has some weird shifts and twice from reverse to drive I had a delay and it almost felt like the rear axle was going to rip off the truck.  
 

I’m wondering if anyone with the k2’s have high miles on an 8 speed with no problems other than some clunkiness.  Every time I drive the truck I’m reminded how the Sierra trans failed and all the problems the 8 speed  had.  
 

[SILVER SLED]

Although my truck is an 18, I love this 8 speed.  It shifts great and has no clunking, or harsh gear changes. 31,000 miles.  I drove a 19 5.3 8 speed for a weekend and it shifted and drove great.  I’m thinking/guessing  that since the 17 and up transmissions have different tcms, the new programming allows them to drive and shift better than the 15-16s do.  

[Booger T]

I wonder how many people that have the harsh clunk when going from reverse to forward are still moving in reverse when they are shifting into forward. Not saying that there aren't some 8 speeds with problems but I don't think they are all related to the tranny itself. Having owned a 19 with the 8 speed I had absolutely no problems with it in the 21k that I had it.

[Ranger522vx]

I learned early on the 8 speed needs some time to settle when shifting from reverse to drive or vice versa.  I wait and sometimes it still happens.  I will say my 19 is leaps and bounds over my 15 sierra.  I’m just hoping it’s an inconvenience and not something I will be spending thousands of dollars on prematurely in the future.  That’s why I’m hoping to hear people with high miles say it holds up over time.  

[michigan2500hd]

I think I have about 85,000 on my 2015 6.2 8 speed. It has sloppy shifting, mostly it won't downshift into 2nd or 1st unless all the way stopped. Other than that and a few bugs at first I  tolerate it. I do like how it shifts when you floor the gas though.

[batman900]

Was about to make this same thread if I couldn't find one. Anyone else with a high mileage 8 speed with or without issue?

[TXGREEK]

32k miles on my 2018 6.2 8speed, took it in after noticing odd feeling gear change, just spoke with my service tech and said they’re installing new “Throttle Body” wow! You just never know what they’ll find next lol

 

 

Sent from Above

 

 

[TXGREEK]

Heads up, picked up the truck after new transmission throttle body was installed and rides “fantastic!” well, looks like I’m keeping my truck longer lol


Sent from Above

[tlaw91]

8 speeds are good transmissions. Shift like crap sometimes, they don’t go bad though.

-Certified GM tech


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[TXGREEK]

8 speeds are good transmissions. Shift like crap sometimes, they don’t go bad though.

-Certified GM tech


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[emoji1303] It’s definitely a dramatic difference after the throttle body was replaced, very smooth shifting.


Sent from Above

[wakawaka]

Not really answering your question but my truck occasionally has the same delay when shifting from reverse to drive too - sometimes bad enough to chirp the tires which is a real treat in a busy parking lot. I took it to the dealer at 20K and was told it's normal and GM won't do anything about it. 40K miles later I'd say it's about the same, if not slightly worse.

 

Really my only serious complaint with the truck.

[500sks]

this is what I wanted to hear

[CadillacLuke24]

15 Silverado with 146k and counting

 

 

1-2 shift, is a tad leisurely in the mornings, improves as the truck gets to operating temperature. Otherwise my 8 speed is a beast. Very reliable. Thinking if I retorque  the valve body bolts at my next trans service (151k) that should help with the 1-2 shift. 

 

Fluid always has looked good coming out too, got that nice new(er) trans fluid smell to it and the same color as going in. 

[tlaw91]

15 Silverado with 146k and counting
 
 
1-2 shift, is a tad leisurely in the mornings, improves as the truck gets to operating temperature. Otherwise my 8 speed is a beast. Very reliable. Thinking if I retorque  the valve body bolts at my next trans service (151k) that should help with the 1-2 shift. 
 
Fluid always has looked good coming out too, got that nice new(er) trans fluid smell to it and the same color as going in. 

That will not help.
You can have a service fast learn done or have the valve body replaced or have the wiring harness replaced for a failing temp sensor. That’s it.


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[2018GMC]

13 hours ago, TXGREEK said:

 

It’s definitely a dramatic difference after the throttle body was replaced, very smooth shifting.


Sent from Above

 

What issues were you experiencing?
Did your 8 speed have the original fluid in it?

I think all the 8 speed prior to new body style t1xx came with the Mobil hydroscopic trans fluid which can accumulate moisture over time and cause shifting issues. 

 

My 2018 has original fluid, only 10k miles but no issues other than occasional light clunk if you let off gas in traffic and it upshifts. 
 

Did you mean transmission valve body was replaced?