Six speed trans life expectancy

[IHscout]

So my new to me 2014 Silverado with 95,000 miles just lost its transmission in the first week of me owning it. 

 

In calling around to local transmission shops the general consensus is that these transmissions will only reasonably last 80 to 100 thousand miles without either the pump or torque converter going out. 

 

Anybody have any thoughts or similar findings?

[Barman84]

Mine lost it at 58k.  Got a free one under warranty had a whole 2 months left.  They gave me utter hell as I have a lift and 35s that were installed by the dealer...  I told them to pound sand and fix it or refund the cost of the lift and tires they did and pay for it with that.  

 

Needless to say say I got a new one.  However, since that I upgraded my diff ratios to 4.10s from the 3.08s it had my trans temps seem to be way better.  The issue is heat with these apparently.

[IHscout]

Good to know as mine is lifted on 35’s as well.  Supposedly bought that way from the dealer.  Also unfortunately with the 3.08 gears. At first I was really disappointed with that fact alone. Even if it was stock suspension and wheels it’s almost useless as a truck. Needless to say I didn’t do my homework in this one. Twice as frustrating is that my wife drives a 2015 suburban with the same drive train and almost identical miles. So I still have a time bomb in the garage. Should have kept my 20 year old Powerstroke at this rate. 

[Grumpy Bear]

There use to be this kid in a town I grew up in I saw on the 'mile' but never really knew except that he wasn't shy about the use of the loud pedal, power braking clouds and neutral drops abundantly.  

 

He stops by my shop one day asking about a C6 I'd just freshened and put on the board. He want's to know what warranty I am willing to provide and wants me to take his check. None and no. Cash and to the end of the drive I tell him. "I've seen you drive". He tells me I must be a crap builder. Whatever. 

 

Look, a box last as long as it last and that is subject to the use and maintenance it gets. Yea, yea, yea, everyone makes a lemon and some, granted have weakness it doesn't take much to exploit into a major problem. They ALL do. Treated right the 6L80E and 6L90E are good boxes. Treated other, you get other. 

 

[Nitrousbird]

6L80E had 161k on my Escalade EXT when I sold it.  New owner has put another 15k on it and still going. 

 

Tranny fluid looked like hell when I bought that truck.  I changed it out (proper line pull change; no flushing or pan drain BS).  Put a monster cooler on it.  Shifted fine and handled some hard towing.  

[Grumpy Bear]

6 hours ago, Nitrousbird said:

6L80E had 161k on my Escalade EXT when I sold it.  New owner has put another 15k on it and still going. 

 

Tranny fluid looked like hell when I bought that truck.  I changed it out (proper line pull change; no flushing or pan drain BS).  Put a monster cooler on it.  Shifted fine and handled some hard towing.  

Three ways to destroy a transmission. Heat. Abuse. Neglect. It only has two failure modes. Mechanical failure or wear. Wear is directly related to heat. The other by load beyond design or defect in materials or workmanship. Change the fluid. Keep it cool. Control the load. It is absolutely within your control if it isn't flawed. Few are flawed. 

[njk4o5]

my 6 speed had 93k when it went

 

after chevy fixed it under warranty i tossed some 35's on it. I doubt itll last another 50k with the way it shifts

[Grumpy Bear]

So fix it! 

 

[KARNUT]

We bought a 88 Ford one ton diesel new. We put 285K miles on it mostly pulling a large prowler. At 100K the C-6 transmission needed rebuild. Shortly after we put a banks kit on and mechanical overdrive. At trade in 185K miles later the transmission was still going strong. The only thing we did at the 100k rebuild was add amsoil synthetic trans fluid, nothing else.


Sent from my iPad using Tapatalk

[00pooterSS]

I've heard mixed things about the 6L80. Mine has 130k and it's doing great. A buddy of mine that has a 2500 truck that's far overloaded never once serviced his trans and it went 240k. I'm sure it's a 6L90 but it's mostly the same trans.

 

My most trusted trans builder said they fail a lot around 100k due to pump failures. I got my truck with 113k so I got nervous and looked around. The thing I found that I will do is this... being so new there are low mileage used 6L80's everywhere. Scrap yards sell them for around 1200-1300 with 20k miles. Or you can go new for 3-4k. 

 

From what I understand Jasper has one they sell that comes with a 100k mile warranty, I haven't confirmed it though. 

[swathdiver]

GM put thermostats in the K2s and that of course raises the fluid temperature for best efficiencies save durability.  The 6L80s in the GMT900s seem to require overhauls after 160K miles in general.  They are made to take a lot of heat but if subjected to such, the fluid should be changed sooner.  Mine has the factory external cooler and doesn't get to the minimum temp to even check the fluid level when on the highway.  

[truckguy82]

33 minutes ago, swathdiver said:

GM put thermostats in the K2s and that of course raises the fluid temperature for best efficiencies save durability.  The 6L80s in the GMT900s seem to require overhauls after 160K miles in general.  They are made to take a lot of heat but if subjected to such, the fluid should be changed sooner.  Mine has the factory external cooler and doesn't get to the minimum temp to even check the fluid level when on the highway.  

All k2 v8’s have the factory cooler, and they all reach their operating temp

 

if you have a thermostat, which we all do, how on earth would it not reach design temp

[Grumpy Bear]

3 minutes ago, truckguy82 said:

All k2 v8’s have the factory cooler, and they all reach their operating temp

 

if you have a thermostat, which we all do, how on earth would it not reach design temp

Oh oh can I answer?  His is a 2009. My 2015 is thermostat delete by....me

[00pooterSS]

18 hours ago, Grumpy Bear said:

Oh oh can I answer?  His is a 2009. My 2015 is thermostat delete by....me

 

Is there a write up on removing the t stat you can link me to?

 

Is the thermostat in the adapter block on the side of the trans where the lines connect?

[Grumpy Bear]

33 minutes ago, 00pooterSS said:

 

Is there a write up on removing the t stat you can link me to?

 

Is the thermostat in the adapter block on the side of the trans where the lines connect?

There are two You Tube videos on it but no writeup I can link you to. That said....

 

What you are calling the adaptor block is actually the thermostat. 

 

 

See that snap ring in the top? Push down on the cap and remove the snap ring. The cap and the internals are now free to be removed. Under the cap is a spring and thimble under that is a 'pill'. The actual working part. Turn that pill upside down and reassemble.

 

Another method has you removing the guts completely. If you chose that method you have to drill and tap a pipe plug into the area the pill rest upon to isolate the inlet from the outlet. I used the first method. I like the idea the spring remains in place assuring the cap is well seated against the snap ring and leak free.

 

If you have a bench vise and a socket with an OD a bit smaller that the Snap Rings ID and let the vise do the heavy work this goes much smoother. It is a stiff spring. Apart isn't a problem. Together takes three hands.

 

Important note. That top line is the output of the pump and the lower line the return from the cooler assembly. The factory thermostat DOES NOT have a minimum flow bypass. It is fully internally bypassed when under it's 195 F set point. When under the trip temperature the outlet is fully 'short circuited to the return and removing either line will thus make it appear as if the lower line is the output. It's important if in the future you decide to add a filter or second cooler or change fluid using the internal pump. I  wouldn't but there are those that see that as fine. 

 

Anyway, hope that is useful. At least if you find the video's it will make more sense to you.