I have a 1996 Chevy Blazer LS, and it ran great for some time until I began noticing some problems, which were assessed. We replaced the fuel pump and it ran great for a month or two, and then if you put the petal down and gave it a decent amount of gas, it wouldn't speed up and a loud screeching/humming would begin coming from the back. We're possibly thinking it's an electrical problem or something along the lines of the catalytic converter? Help is wanted, thank you.

 

The screeching/humming thing would point me towards something more mechanical than electrical or catalytic converter related. Does it only do this when you accelerate hard? Are there any other driveability concerns?

 

Yes, it only does this after accelerating hard and no, there are no other driveability concerns.

 

What do you think could be the problem?

 

If it only happens when you accelerate hard, I would be looking at your exhaust system possibly hitting the driveshaft.

You may want to check the rear wheel bearings as well as do a rear axle service to inspect the gears in the rear axle.

 

What leads you to think it was the gears? The car shifts fine, etc. I also don't understand how you could think it was the driveshaft? Please, fill me in.

 

If the driveshaft was rubbing the exhaust it could make a noise similar to that.

Swartlkk meant the gears inside of the rear differential, not transmission gears. If a gear in the differential had worn teeth it could possibly spin without turning the gears touching it under high load, like if you accelerated hard.

 

And the wheel bearing are easy to check. Just jack up the rear end and rotate the tires. You should hear any problems pretty quick.

 

I appreciate the help, believe me I appreciate it more than anything but I've run all this past my dad, and he says there's no way it could be the driveshaft hitting the exhaust or anything in the gears in the differential. He says it's in the catalytic converter or something along those lines. Is there anything else you could brainstorm?

 

A catalytic converter won't cause a screeching/humming noise. They can rattle. A loose heat shield on the cat can possibly hum or screech, but the catalytic converter itself...