Engine Knock

[Westlotorn]

2001 Denali, 6.0L 320 HP version, Start up piston slap, lasted no more than 15 seconds when cold only. From new to 89,000 miles no change.

[isucowboyvet]

2001 6.0, knocks part of the time. No rhyme or reason. Sometimes when cold, sometimes when hot, sometimes not at all! I switched to mobil1 5-30 with no change????

[Z71Adrenaline]

2001 Z71 w/5.3L. 74,000 miles. knocks at startup, mostly when temps are cooler.. still runs like a champ otherwise!

[jaslo]

Did anybody ever try using different brand of oils to see if that stops the engine knock. I think it is kind of weird that my truck starts doing it with 84,000 miles on it.

[J.B.R.]

99 Yukon Denali 5.7 74,000 miles no konck

78 vette 350 76,000 miles no knock

75 vette 350 110,000 miles no knock

79 2500 p/u 350 250,000 miles Yes knock wrist pin gone

[naterasmussen]

01 Sierra 5.3 w/ 110,000 miles - only notice it on days colder than 40 - wears off after a minute or so.

[GMTRUCKTECH]

The GM knock is well known in the industry. GM went to very short skirt pistons on the new Generation small blocks. 4.8L, 5.3L and 6.0L engines. These have a lot in common with Race Enignes, Long connecting Rods for good rod angle, Short skirt Pistons for light weight and light tension piston rings for reduced friction. Same things they did in Race engines for last 20 years. It works, very efficient, great power and incredible durability. These are the best engines GM ever made. THE NEGATIVE, GM was new to this Short skirt piston stuff back in 2000 and it took them till 2003 to fix the Piston slap at start up. Once heat hits the piston they grow and quiet down. Colder climates will cause this effect to be larger and warmer climates make it better. Some engines are a little tighter than others and may have no noise, some are looser and make far more noise. They will all run 200,000 miles without breaking a piston skirt which is the only complaint known to be caused by piston slap. If pistons are installed TOO TIGHT they can stick in the bore while you are working the vehicle hard, commonly called Piston Scuff. This problem is far worse than piston slap causing an irritating noise on start up. With this in mind GM was very slow to tighten up the clearance on the new GM family of small blocks. These turned out to be great engines, any production engine rebuilder will tell you they never see one of these in for repair unless the owner abused it to death. No oil changes, overheated it or some combination of these offenses. Hope this helps. Hold the RPM at 2,000 for about 10 seconds to put heat in the pistons and the noise will go away as they grow larger in the heat.

02 1500 knock all the time louder when cold. traded for 04 1500 no knock

[swattley]

i have a 97 full size with a 350 v8 and it has the slight knock when first throttleing up if the engine is not allowed to warm up. but it has done this since new i think.

[jhm]

My '01 4.8 sat for only 4 days while I was on a trip. When I got home I started it up and had knock/ticking for about 45 seconds. Since it was hot outside, it cannot be related to oil viscosity. Actually sounded like the lifters bled down. I have had some noise in the winter when the temps get way down, never in the summer. Piston slap????

[BigJayDogg3]

2001 1500 HD 6.0L About 90000 mi.

I wouldn't know if it knocked at startup as I let my truck warm up if I start it cold. I normally start it in the morning, let it sit for about 5 min while I finish getting ready to leave then I get in and go, so if there is knock at startup I wouldn't know about it. I guess that's something I have to check.

 

It used to knock when you would pull off from lights, but after I changed to 91 oct. all problems with that were solved.

[obyone]

'00 Silverado 5.3 60K miles when sold no knock

'02 Denali 6.0 38K miles no knock

 

must be all that salt air....

[RPMGUY]

Hello, my name is Ryan. Im a new member trying get some replies.

 

My Nissan pu had a bad knock on startup. I changed out all the timing components and noise is gone.

 

Do you think the knock is rods or timing chain or lifters?

 

I want to post a topic, but cant. Do you know if they made the Quadrasteer in a 2500HD with extened cab and long bead? And or 8.1 with Quadrasteer? Thanks Ryan

[rsg]

Start up knock quite noticable on 2001 6L. Two bottles Techron and went from Mobil I 10-30 to Castrol GTX 10-30 and start up knock is 95% gone. No rhyme or reason but I am happy it is mostly gone.

[choptop]

I have had several gm trucks from 99-04 that all had the knock that was said to be caused by the piston skirt design on the LS1 engines.Don't know for sure, but do know that knock decreased or disappeared after switching to synthetic. I didn't think it would on the first truck and it did. Thought first truck was a fluke, wrong again.Synthetic fixed the problem, and had decreased or stopped it on 7 other trucks as well.Don't know why, just does.

[Z71Dave]

2005 Silverado Z71 18,600 miles NO knock

 

2003 Suburban 1500 4X4 36,900 miles NO knock