1999-06 ls engine question?

[mopower440]

On the 1999-06 4.8 and 5.3 engines, when they finally fail after hundreds of thousands of miles, what is it that usually fails in the engine? I know ive seen MANY with 300,000 miles on them and still going strong, but when they finally give up, what is it that goes? Im thinking the roller rockers or roller lifters being they have the small needles bearings in them, but i dont know and am wondering?

[blacstar]

it will really depend on how they were maintained, how they were driven. you have too many factors to account for.

[kerrige]

Lifters and pushrods are common issues. Almost never bottom end stuff it seems like its always valve train related.

[demonheavymetal]

Lifters and pushrods are common issues. Almost never bottom end stuff it seems like its always valve train related.

Same....usually something in the top end goes first

[CHEVROLADE]

Yup uncle had 300 k miles on his 5.3 and only thing failed was rocker bearings

[mopower440]

This is why i asked this: I have a 1999 extended cab 4x4 with the 4.8, it has 211,000 miles on it and runs just fine and uses absolutely no oil and oil stays clean betweem changes. I just got back from a long trip with it, 1150 miles each way and she did awesome. I plan on doing this trip probably every year and wondering at what mileage should i start getting concerned with the engine failing on me as i dont want to get stuck on the side of the road somewhere on these long trips..Figured at some point i need to swap in a lower mileage engine to be safe, but when? what mileage should i start considering swapping in a lower mileage engine?

[Botlfed]

To be honest man, with good upkeep, change the rockers, lifters and pushrods, get some injector cleaner, or just clean em by hand, i dont see any reason to change the motor on a non aggressive driven truck. probably around 250-275k or maybe even now if you have the money take care of the above mentioned stuff and keep driving it man. Also beware of the transmision shift solenoids, 25$ part could make you think youre losing your trans. the 4.8 in my crew cab isnt coming out til it falls out on the highway.

[demonheavymetal]

Lookup a top end rebuild kit on summit, give u an idea of what you'll spend to get another 200k+ of reliable mileage

[mopower440]

so the bottom end wouldnt need anything for another 200k miles? how does the rod and main bearings and rings go 400,ooo miles?

[Paulster2]

Bottom end is strong ... I don't have a longevity quote for you, but what they are saying above sounds about right. Biggest thing to worry about on these trucks is the 4L60 trans, besides the little wear items (ball joints, bushings, u-joints, etc.). They seem to sneak up on you when you least expect it.

EDIT: To give you an idea about how stout the bottom ends are on these engines, Hot Rod Magazine (or was it Chevy High Performance) did an article a couple of months back utizing a 4.8L motor. They were actually trying to see how much boost they could throw at it before it would break. They put in the neighborhood of 30+ dyno runs on a STOCK engine with 100k+ miles on it, pushing 28+ psi of boost on a twin turbo setup ... thing put out over 1200 FWHP ... and never broke. They ran out of dyno time before they finished what they were doing. Mind you this is a magazine, but I think it should give you an idea of what these engines are capable of.

EDIT #2: Here's the original story in Hot Rod Magazine: The Big Bang Theory What is funny is they originally thought it was a 5.3L, but later found out it was a 4.8 ... gnarley.