Help...engine Noise Question

98 Z71 SLT · July 21, 2007

Thinking about purchasing a 1995 GMC Suburban 1500 with a 5.7 350 K engine. Throttle body injected, 2-wheel drive.

Truck has 112k miles on it. Dealer (My employer) is waiting to hear a response if I want to purchase. I have checked this truck out at work (New-Car store-this truck is a trade)

ONE thing sorta holding me back. While driving the truck OR sitting in park, if you snap the throttle, aroung 1800 rpm's I am hearing a

Rod knock??

Wristpin??

Piston Slap??

OK...here's the kicker...2000 rpm's and above...THERE IS NO ENGINE NOISE.

At cold engine start...overnight...NO ENGINE NOISE

At idle...engine hot...NO ENGINE NOISE

Am I hearing a rod-bearing on it's way out?? Am I hearing NOTHING UNUSUAL???

Another tech listened to the noise yesterday...which mainly occurs when ENGINE IS HOT, and he stated "...it sounds too "tinny" to be a rod bearing. Check the torque converter bolts."

So, after work I pulled it in the shop, and all the torque converter bolts are perfect. No cracked flywheel. No leaks under the truck. I also changed oil and filter. NOTHING found in the oil or filter.

What in the world am I hearing??

I always thought these 350 K engines were BULLETPROOF.

As stated earlier...at 1800 rpms the noise is most prominent. Oh...awesome oil pressure too...40 psi when HOT at idle.

Do these old throttle body engines "loosen-up" when they get miles on them?? Is this engine gonna break??

Should a different type of engine oil / additive be used????

HELP - input needed.

Cdale2k · July 21, 2007

My buddy has one of these, only his is a 4 wheel drive. It has the same problem and has for about 2 years now. We have stripped it down, looked at everything and replaced all the bearings, Rings, and gaskets. The noise stopped for mabey a day and came back. Personally i think that it may be nothing to major.