I noticed now that it has gotten colder out my 95 LS 160k miles has a slight knock when started cold.
Same as the others goes away in a few seconds but is there when first started.To me it sounded like a lower end noise...Ony when first started ...And here I thought Gm fixed the 2.8 with the 4.3 go figure!!! Several years ago I had a 85 Tahoe with a 2.8 which ended up dropping a crank at 130k....

 

Noise on Start-Up but Only Lasts a Few Seconds

[*]Improper oil viscosity. Install the recommended oil viscosity for the expected temperatures.[*]Worn or dirty valve lifters[*]Excessive piston-to-cylinder bore clearance[*]Excessive piston pin-to-bore clearance[*]Excessive crankshaft bearing clearance [/ul]


Knocks Cold and Continues for 1 to 2Minutes

[*]Loose or broken crankshaft balancer or accessory drive components[*]Excessive piston-to-bore clearance A cold piston knock which disappears in 1.5 minutes should be considered acceptable.[*]A cold engine knock usually disappears when the specific cylinders secondary ignition circuit is grounded out. [/ul]

 

Piston Slap!! My 2000 Blazer does it too. Look at www.pistonslap.com. The web site is kind of a scare tactic in my opinion, because i have seen alot of these motors with well over 150k on them and they run like a top. But the site will at least tell you about your condition. Korey

 

So let me get this right, The trans slightly surging forward on startup is normal,The engine with a slightlower end knock on startup is considerednormal.lol I've got that great Gm Feeling. I should have gotten dinner and a movie with this truck....lol I still like the looks of the truck!!!
My Subaru Outback Sport with the same mileage is such a better engineered vehicle it isn't funny...

 

Here ya go...

https://blazerforum.com/m_56798/tm.htm

 

Mine hasn't done it so far, or at least that I've noticed... and the coldest it's been since I got it is-20 degrees C (about -4 degrees F)... I'll start listening more closely though, from now on and let ya know if it's there...

Side note: haven't used my block heater yet, lol, I guess I should probably dig it out incase we get another shot of -40... I figure if my old out of tune '85 S10 can start without being plugged in, I don't have to worry so much about the new one... (Yes, I know it's easier on the engine, but I have no set schedule for when I go out, lol)

 

Piston slap. As an ex-Volvo guy I am no stranger to it. Won't hurt anything, it's strictly a noise.