Silverado 5.3 update 12/11

[64nailhead]

Non DOD valley cover for a DOD capable block :

12598832 Gen 4 LS Non AFM DOD Valley Cover With Gasket for 4.8L 5.3L 6.0L 6.2L | eBay

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www.ebay.com

This is what is underneath a DOD valley cover:

https://www.amazon.com/dp/B09R65NPT8/?tag=gbody-20

When the valley cover bolts loosen, then the DOD lifters get activated with LOW oil pressure and the pushrods on those lifters get the ends ground off from them. And the motor looses oil pressure as well. Grinding up pushrods always aids in the usual result of fine particles of metal being sent into the oil pan.

I know alot of us don't have the time or the availability to junkyards, but if you were one to do some investigating of this, head off to the local scrapyard and pull some DOD valley covers and pushrods on high mileage motors and see what you find - it will be obvious after you see 4-5 of these things what the issue is. Of course this not speedy - the intake and related parts have to be removed to access, and both rocker arm assemblies under the valve covers. I'm yet to pull apart a high mileage DOD motor with the 8 DOD pushrods in good (re-usable) condition.

Rt Jam the only maintenance I know of is monitoring your oil pressure. If you see it start dropping then check the valley cover bolt torque as the 1st step. Changing the 8 DOD lifters is a PITA - 'Off with their heads!'

One positive not about changing the lifters is that it's much easier to get out the 3-6 broken exhaust manifold bolts with the heads off 😉

 

[86LK]

Has anyone tried just replacing the lifters, before they fail. I'd be happy to know a complete refresh would get me another 150,000km's.

doubt it. they've been known to fail after 50k, get fixed, then fail after another 10k. seems to be completely random. I even came across an article where it failed on a brand-new vehicle within 1 day of being driven off the lot with less than 200 miles!

 

[Rt Jam]

It's a very big decision on a car since the engine needs to come out to get the heads off.

You and I have definitely heard the stories but you are Only hearing the failed. There are thousands of trucks out there still running on DOD. My car is not babied, I floor it often and it's been to the track a few times. My friend's Impala SS has over 300,000km and he does not treat it well.

I hear you on the reliability and who does not want a reliable vehicle, especially when the failure is metal in the engine but this is about a 30% loss in mileage to delete it.

 

[Supercharged111]

It's a very big decision on a car since the engine needs to come out to get the heads off.

You and I have definitely heard the stories but you are Only hearing the failed. There are thousands of trucks out there still running on DOD. My car is not babied, I floor it often and it's been to the track a few times. My friend's Impala SS has over 300,000km and he does not treat it well.

I hear you on the reliability and who does not want a reliable vehicle, especially when the failure is metal in the engine but this is about a 30% loss in mileage to delete it.

No way Jose. We saw NO perceptible difference in fuel economy. Oil economy on the other hand was notably improved.

 

[Rt Jam]

Who is Jose and what are or were your numbers? Or did it just seem the same?, Yes, you did say perception.

I typically get 12 to 15L/100km on my daily commute. The mileage is crap since I do not drive to get good mileage and in traffic it will never go into 4 cyl mode.

There was a long trip from Ontario to the U.S. east coast. This was 95% highway at 120km/hr, cruise control, used 3 tanks of fuel. Also compared actual fuel quantity vs distance to the cars average mileage readout. First 87 octane returned 8.3L/100km. 89 octane was 8.1L/100km. 91 octane was 7.7L/100km.

From comparing this mileage to other cars I have owned. I'm confident there is Zero chance an deleted LS4 would get 7l?100km.

I'm aware some will have problems understanding the metric mileage measurement. Just know the smaller number is better. Less fuel used for a given distance. Google tells me 7.7L/100km is about 30mpg. In 8000km my oil is still above add.

 

[86LK]

Who is Jose and what are or were your numbers? Or did it just seem the same?, Yes, you did say perception.

I typically get 12 to 15L/100km on my daily commute. The mileage is crap since I do not drive to get good mileage and in traffic it will never go into 4 cyl mode.

There was a long trip from Ontario to the U.S. east coast. This was 95% highway at 120km/hr, cruise control, used 3 tanks of fuel. Also compared actual fuel quantity vs distance to the cars average mileage readout. First 87 octane returned 8.3L/100km. 89 octane was 8.1L/100km. 91 octane was 7.7L/100km.

From comparing this mileage to other cars I have owned. I'm confident there is Zero chance an deleted LS4 would get 7l?100km.

I'm aware some will have problems understanding the metric mileage measurement. Just know the smaller number is better. Less fuel used for a given distance. Google tells me 7.7L/100km is about 30mpg. In 8000km my oil is still above add.

you're getting 30mpg? what vehicle are we talking about?

I have found that while my MPG in the city has been affected somewhere between 1.5-2mpg, my mpg on the highway has barely changed. maybe 0.5mpg? it's hard to say because I've taken 2, maybe 3 long trips, in my truck since Oct 2019, just before Covid hit. and the last was after I disabled AFM. but it was practically the same route as the first two. practically no difference in mpg.

 

[Supercharged111]

you're getting 30mpg? what vehicle are we talking about?

I have found that while my MPG in the city has been affected somewhere between 1.5-2mpg, my mpg on the highway has barely changed. maybe 0.5mpg? it's hard to say because I've taken 2, maybe 3 long trips, in my truck since Oct 2019, just before Covid hit. and the last was after I disabled AFM. but it was practically the same route as the first two. practically no difference in mpg.

You need to get some wind in your life. That will absolutely murder your hwy mpg.

 

[scoti]

you're getting 30mpg? what vehicle are we talking about?

I have found that while my MPG in the city has been affected somewhere between 1.5-2mpg, my mpg on the highway has barely changed. maybe 0.5mpg? it's hard to say because I've taken 2, maybe 3 long trips, in my truck since Oct 2019, just before Covid hit. and the last was after I disabled AFM. but it was practically the same route as the first two. practically no difference in mpg.

Did you disable only or disable + swap to non AFM/DOD parts as well?

 

[86LK]

Did you disable only or disable + swap to non AFM/DOD parts as well?

disable only, still has AFM parts
lifter #7 got jammed. tore down the top, inspected with flashlight and camera, didn't get twisted and lobe looked ok, knocked the lifter loose with pushrod and hammer, connected computer and Disabled AFM. been running fine for the last 20 months.

 

[fauxfour2]

I am watching this thread with interest. I have a 2008 Suburban with 113K miles on the 5.3. I used a diablo tuner to do the 87 performance tune (which i dont think does much) but i also diabled the DOD. Anything i should be looking out for? I have a solid 40lbs of pressure at idle all the time. Up to 60lbs while driving. Sorry for semi-hijacking this thread lol.