Extreme Grind Upon Acceleration

[JPVortex]

94 k1500 350 tbi with a 4l60e. Driving home from work tonight an extreme metallic grinding noise started directly below the cab. It starts as soon as I accelerate and let’s up when I let off of the gas pedal. It DOES NOT happen when in park revving the engine.

Here’s my 2 theories:

1. Starter bendix is not properly disengaging after starting the truck which when the vehicle is moving is causing the flex plate to hit the starter bendix gears(feel like this is not likely)
2. Sucks to say this but I’m suspect of the transmission or transfer case. Something like the planetary gears or something being sheared? I hope not, don’t want to pull the transmission again but I feel it’s more likely than the starter option.

There’s a couple videos but it’s hard to hear, headphones may help. Thanks.

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[NickTransmissions]

Upload another video without you talking, very hard to hear the sound itself over you. Make the video at least 20 seconds long. Meanwhile check the flexplate. Doesnt sound like transmission from what little i was able to discern plus you'd have little to movement after a short while if the gear train was eating itself.

 

[movietvet]

That noise may be exhaust related. WAG! Or you have a fan rubbing a shroud when you accelerate. If it does not happen at idle or when coasting or just maintaining speed, it could also he a heat shield of some sort. Again, WAG's.

 

[JPVortex]

Upload another video without you talking, very hard to hear the sound itself over you. Make the video at least 20 seconds long. Meanwhile check the flexplate. Doesnt sound like transmission from what little i was able to discern plus you'd have little to movement after a short while if the gear train was eating itself.

Will definitely try to get a better video tomorrow. And yeah it may not be the transmission. It still shifts like it should. Also going to look into the ujoints and transfer case.

Will jack up one rear tire in neutral and spin it and I’ll see if anything sounds out of place.

 

[JPVortex]

That noise may be exhaust related. WAG! Or you have a fan rubbing a shroud when you accelerate. If it does not happen at idle or when coasting or just maintaining speed, it could also he a heat shield of some sort. Again, WAG's.

Thanks! All stuff I’ll check.

 

[movietvet]

Have a friend power brake it and goose the throttle and watch for an engine jump. Make sure you use wheel blocks when you do that.

 

[JPVortex]

Have a friend power brake it and goose the throttle and watch for an engine jump. Make sure you use wheel blocks when you do that.

That’s a good idea! So the drivetrain will be under load.

 

[JPVortex]

So my buddy has a 92 k2500 and a couple years ago his tcase went out and made this sound when driving. It sounds almost just like mine except a bit louder(he said it was quieter when it first started but this video was a day or 2 before the tcase completely gave out and the truck wouldn’t drive)

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[GoToGuy]

U joints, get under and touchie, wiggle, inspect. In neutral, both rear wheels off the ground, spin wheels axle bearings ? Hand turn drive shaft feel, listen to u joints. Same up front.
Does not make noise in neutral and park. Eliminates the starter gear hanging up. ( Plus u would have blown it up with eng RPM, it won't do 2500 RPM , Grenade)
So process elimination, happens in drive with movement. Does the sound follow speedometer ? Does it also make noise in reverse? Therefore a drivetrain related , between transmission to wheels. Unless something other shows up, that's where I would concentrate. Go from there. Good luck.

 

[Hipster]

Your problem doesn't sound like his. agree not likely starter.