so i made another post a while back about the radio making a buzz on acceleration but it stopped at 2k rpms in 3rd gear. now when slowing below 2k rpms at like 50mph to about 600rpm at 10mph i can hear what i thought was like a howl/whine. talked to a friend and he said if it isnt grounded right it can do this. this also started after i switched out the old 115alt to the 135. im in the middle of a 2k mile trip and last night i noticed it was buzzing but then went away later. there is no other problems with the truck, drives fine, got 18.5 mpg from mississippi to texas last night.

i know it isnt a leak in the up pipes(sadly i wanted to get new headers/y pipe) if i put it in neutral and rev there is no noise. so im thinking about just ordering the bigger gauged wires and re wiring the batteries and alternator but i remember someone saying its easier to just link

anyone ever had electrical buzz when rpms go up or down with a load?

Can you verify the connections, positive leads are all tightened down on the alternator. Verify you have good voltages on the ficm and battery after glow plug cycle.

Where did you get your new alternator from?

i believe the alt was a MC i got from oreillys, ill check terminals. voltage for ficm was fine. new batts recently aswell. ficm voltage was 47.5-48 and the other voltages for the ficm i can see were 13-13.5

It sounds like your head unit could be picking up feed back.. do you have an aftermarket radio or stock?

stock unit. but the guy before me had a system. the acceleration hum is different sound from the decel whine/howl. it also is coming from a different area. like right behind the dash almost

okay check battery terminals tight. checked cable on the alt. tight. checked driver side ground. tight. couldnt find ground for passenger side

Even though you said it was a MC, it may have been bad out of the box. I had the positive post nut loose on my Mustang and it led to a flickering battery light and radio feedback too. Try powering the radio off next time it does it.

i checked alt, its all tight and i have watched my battery voltage and it reads fine. altho yes it indeed could be bad.

my alternator has the 1 red cable with a nut on it and then the pigtail with a plug into it with only 2 small wires. is this right?

It's been awhile since I had my truck. But yes, that's all I remember being in the connector. See if repeating the sound during your next drive can be eliminated by powering the radio off or switching input.