Grinding noise when in gear

I got a 1995 s-10 blazer with 158,000 miles on it, I hear a grinding noise when its in gear, but the noise goes away in park or in neutral. The noise gets louder with engine rpm. It happens even when the truck is NOT moving. It cant be any of the pulleys or accessories cause it goes away in neutral or park. I did compare to the howling sound that comes when its in 4-HI. The noise is different than that, besides the howling sound goes away when i switch it back to 2-HI, which is normal. so what you guys think about this???

Cat could be shot.

CPI injector and nut kit could be leaking ruining the cat as well.

anything touching the ole' driveshaft?



I got a 1995 s-10 blazer with 158,000 miles on it, I hear a grinding noise when its in gear, but the noise goes away in park or in neutral. The noise gets louder with engine rpm. It happens even when the truck is NOT moving. It cant be any of the pulleys or accessories cause it goes away in neutral or park. I did compare to the howling sound that comes when its in 4-HI. The noise is different than that, besides the howling sound goes away when i switch it back to 2-HI, which is normal. so what you guys think about this???

anything touching the ole' driveshaft?
no nothing is touching the driveshaft, besides its not even turining when the vehicle is at rest. I got a new cat and new CPI and nut-kit. It sounds like there something wrong with the torque converter or the tranmission fluid pump. But thanx u guys for the suggesttions. I'll still take any more suggestions..it wont hurt

I would get under the truck and check your exhaust hangers and the little rubber boots and grommets that hold them all together. I had one break on one side that did not drop the whole exhaust out of the truck, just let it shift ever so slightly to one side. Enough to make it rub and "grind" at idle with the truck in gear. Sometimes that grind would turn into a full blown metallic squeak/ratt-a-tap-tappity-griiind with the air conditioner on. Crawling underneath the rig found me a little broken loop of rubber exhaust mount. Picked one up from my "specialty" exhaust place just down the hill from where I live and muscled the exhaust up and slipped the new bootie on. Problem went away! WD-40 helps to get the old, broken bits off, and squeeze the new one back on - and applying the use of a pair of stout slip-jaw pliers... But yeah, get a look at your exhaust and make sure *all* of the little rubber grommet/hangers are in place and happy.

I would get under the truck and whack the cat with the palm of your hand and listen for a loose rattle inside.

I would get under the truck and whack the cat with the palm of your hand and listen for a loose rattle inside.
I have all of these things and exhaust sysytem look good to me. Its not exactly grinding sound, its more like whining sound

Trans front pump going bad
How the trans fluid ???? full and clean