Thoughts/Input on GM engines appreciated

[rayra]

I get that it's happening but I don't know how AFM is impacting the lifters as they are getting oil regardless. It's as if the LACK of firing in the shut off cylinders is somehow affecting the pressure on them. But that ought to be a reduction in pressure too. And IIRC those are roller lifters, too, roller on the cam end. Both the '02 and later engines. I just don't understand how AFM could be screwing that up, but it's happening. And in particular the 07-08 models. The 07 in particular are also having high cylinder wall wear in the shut off cylinders. Its ass if the LACK of combustion pressures is giving things enough freedom to float around and wear things out.
Anyway, avoid the 07-08 models, the first two years of the GMT900 series. Which means the '06s are the last of the useful full-framed models.

and IIRC GM killed the 2500 in the SUVs after the GMT900 series ended, 2013. So 2009-2013 is about it for a GM 2500 SUV.

 

[plumber mike]

I have had just about all of the modern GM engines and have been very happy with all of them. My wife’s 07 Tahoe is going to go soon at 145k so I can remain fond of them. I’ve had both 6.0 and 8.1 that hit 300k problem free.

 

[02TahoeMD]

I get that it's happening but I don't know how AFM is impacting the lifters as they are getting oil regardless. It's as if the LACK of firing in the shut off cylinders is somehow affecting the pressure on them. But that ought to be a reduction in pressure too. And IIRC those are roller lifters, too, roller on the cam end. Both the '02 and later engines. I just don't understand how AFM could be screwing that up, but it's happening. ....

Dunno just how, only know what the mechanic told me. I think the shut off cylinder is causing stresses the engineers did not foresee. The mechanic told me the lifters (which are indeed roller lifters, you are correct) "stretch" when placed under the stress of not firing. Then they stretch too much and bam, you are now driving a vehicle with a V-7 engine. I was quite appalled when I stopped in the shop the day after I dropped it off and saw just what had happened to it.

 

[Choff]

2005 GMC AWD Savana Conversion Van now has 197,569 miles on 5.3, bought it used with 43,000, we have had it 11 years
no issues, no leaks and is our Daily driver.

 

[SpineDocWTX]

My current daily driver is a 92 Ranger with the 3.0 V6. My wife drives an 04 Lexus LS. My toy is an '87 Kawasaki 1000 that I've had for 14 years now. I'm liking the sound of the older less complicated models! I'm not opposed to buying something older. Maybe I can find a nice Grandpa truck like I did with my last 2 vehicle purchases?

 

[XJLI]

The GMT800 trucks are tried, true, and simple machines. Pretty easy to find grandpa specials still. Mine was low mileage but I do almost 20k a year so my 05 just hit 135 this morning.

https://www.ebay.com/itm/Silverado-...ash=item56b3d5fc06:g:9XQAAOSwjkxbgv7k&vxp=mtr
https://www.ebay.com/itm/Silverado-...ash=item3d722ba760:g:Y2cAAOSwd~ZbiMRx&vxp=mtr
https://www.ebay.com/itm/2006-Chevr...ash=item2866718352:g:7MkAAOSwTMZbhaMG&vxp=mtr

 

[rayra]

Dunno just how, only know what the mechanic told me. I think the shut off cylinder is causing stresses the engineers did not foresee. The mechanic told me the lifters (which are indeed roller lifters, you are correct) "stretch" when placed under the stress of not firing. Then they stretch too much and bam, you are now driving a vehicle with a V-7 engine. I was quite appalled when I stopped in the shop the day after I dropped it off and saw just what had happened to it.

That kind of fits with what I'm imagining is happening, that somehow the lack of combustion stresses is allowing the non-firing cylinder components to beat themselves to death. But then again I haven't seen / noticed similar damage reports from the '09 and up models with AFM. Something had to have changed.

 

[rayra]

My current daily driver is a 92 Ranger with the 3.0 V6. My wife drives an 04 Lexus LS. My toy is an '87 Kawasaki 1000 that I've had for 14 years now. I'm liking the sound of the older less complicated models! I'm not opposed to buying something older. Maybe I can find a nice Grandpa truck like I did with my last 2 vehicle purchases?

heh. Well I know just where you can find a very well kept 2005 Tahoe Z71 that's about to turn over 200k mi. Little old lady only drove a daily 50mi highway commute with it. Odometer divided by engine runtime clock = 54.5mph average speed.

 

[SpineDocWTX]

heh. Well I know just where you can find a very well kept 2005 Tahoe Z71 that's about to turn over 200k mi. Little old lady only drove a daily 50mi highway commute with it. Odometer divided by engine runtime clock = 54.5mph average speed.

I'm sure it will find a good home! I need a truck though, don't think my bike would fit in the back...

 

[SpineDocWTX]

The GMT800 trucks are tried, true, and simple machines. Pretty easy to find grandpa specials still. Mine was low mileage but I do almost 20k a year so my 05 just hit 135 this morning.

https://www.ebay.com/itm/Silverado-...ash=item56b3d5fc06:g:9XQAAOSwjkxbgv7k&vxp=mtr
https://www.ebay.com/itm/Silverado-...ash=item3d722ba760:g:Y2cAAOSwd~ZbiMRx&vxp=mtr
https://www.ebay.com/itm/2006-Chevr...ash=item2866718352:g:7MkAAOSwTMZbhaMG&vxp=mtr

That's what I'm talkin' about!

 

[bknudtsen]

That kind of fits with what I'm imagining is happening, that somehow the lack of combustion stresses is allowing the non-firing cylinder components to beat themselves to death. But then again I haven't seen / noticed similar damage reports from the '09 and up models with AFM. Something had to have changed.

If you’ve ever spent time hitting a hanging bag, then you know what it feels like when you step too far out and throw a punch. Elbow snaps and hurts like hell. You need the compression of the bag to prevent damage to your joints.

Same thing, in my mind at least, is happening with the non-firing cylinders. There is no fuel/air mixture to compress and dampen the components, so the piston and connectors snap at the end of the compression stroke, causing an ever so slight over travel.

It’s a theory, anyway...

 

[Buliwyf]

That's a reasonable theory. Good rods and pistons will fail on the end of the exhaust stroke or beginning of the intake stroke. When there's no cushion on top of the cylinder. ,Exactly like your boxing analogy.

No experience with AFM, but my 20 cylinder engines will go into a half or less engine modes under light load. They can start puking engine oil out of the exhaust headers and get ''slobbery'' because the pistons not making power still drag oil up the cylinder walls. But other than a mess, I haven't had any reliability issues.

 

[Climber Rob]

I have an '08 2500HD 6.0L. Absolutely rock-solid truck that I don't hesitate to recommend. Only issue I have had with it is the (common) leaky transmission cooler lines. Mine leak so little I don't worry about it, but I know it's an issue on some vehicles.

 

[great08]

carcomplaints.com is a great resource for figuring out which vehicles had what problems what years. I have had several GM and Toyota trucks over the years and would call them on par with each other for reliability. The chevys are easier to find/more abundant/cheaper/better bang for your buck/easier to work on. Just an IMHO though so not worth too much. What I love most about GM is mentioned above. They tend to use the same thing for not only many years... but on many vehicles as well. Which makes keeping them long term an easy thing to do if desired.

The 5.3 is solid but can sip a little oil as it gets older(while still being reliable)
I have not owned the 6.0 but a lot of folks swear it is the best they have ever owned.

My new 2018 Colorado with the 3.6 (new 3.6 put in in 2017)seems like it is going to be an awesome little engine for this size of truck. Good pep (motor trend tested ~6sec 0 to 60mph), good torque, can drive around and never go above 2k rpm if desired with the 8spd auto(which should contribute to very long engine life). Got 26mpg during a 3 day/300+mi mixed driving commute. Not bad for a 308HP engine and 4WD with all terrain tires.

I love the 4WD Auto mode available these days. You can drive around on dry pavement without binding the drivetrain! AWD vehicles have lost their only advantage.

Did the actual calc at the pump and it worked out to 25.45mpg... which is within pump hand squeeze error. Happy!!

 

[E.J. Webb]

I had to put in a water pump in at 150,000 miles, that is not bad, It dose need valve cover gaskets but no other problems.