I have a 1996 Chevy k1500 with the 5.7 TBI 350. Recently while driving I noticed truck had a loss of power and then started making a loud squealing noise as if metal was scraping metal (Like fingers on a chalkboard sound). Truck then was sluggish on take off and acted like it didnt want to go. I got home and killed truck, when I start truck the squeal is instantaneous and fades out if I give it gas. I took belt off and noise is still there, so i know its not from any pullies or belt. Truck don't overheat or anything, so tells me water pump is ok. The sound is coming from rear of engine, and when you climb underneath sounds like its around the flex plate/torque converter. I read that it could possibly be a cracked flex plate which would explain loss of power and sluggishness. But I'm not a Master mechanic only a shade tree mechanic. Could the squeal be backed out bolts on flex plate to torque converter? Any help on this would be greatly appreciated before I decide to drop the Tranny.

 

Coming from that area of the truck, I’d suspect a locked up torque converter; however a cracked flex plate is also possible.

Loose bolts between the flex plate and TC generally produce a thumping/knocking type sound (almost like a bad rod bearing). And unless the engine or trans has recently been removed, it’s unlikely those bolts are loose.

If there’s inspection plates, remove them (or starter) and have a helper rotate the crank while inspecting for damage. If nothing is found it’s likely the transmission.