Odd noise that I can’t seem to figure out.

[Ryan]

So this noise has been occurring ever since I bought the truck. I figured it was bearings/brakes/rotors on the front at first because it’s kind of like a low quiet grinding sound. so I replaced all on both sides. Even the tires were replaced. I also went ahead and replaced everything in the rear wheels as well. But still at around 40mph+, whether I’m in 4th or 5th I hear and feel a low almost quiet grumbling sound coming from the engine. It can be drowned out by radio, but I still feel it in the steering wheel if I really feel for it. Along with it I hear a grinding noise. As if I’m in too high of a gear for the speeds I’m going. It’s the same grinding sound I hear if I were to switch into 2nd way to soon. I even hear the grinding, when I first take off in first as if first gear is to heavy for the engine to turn at first. It goes away once I’m at a higher point in rpms. Doesn’t do it when I rev the gas in neutral though. Now when I’m cruising, say going a flat 30mph in 4th. Owners manual says this is ok. And over all the engine feels like it doesn’t mind cruising in 4th at 30mph, but I hear that faint grinding sound and it makes me think otherwise. When I reach 40mph+, and cruising at those speeds, I hear the faint grinding sound too. Doesn’t change pitch or volume. Stays the same all the time. I’ll have it in 5th cruising at 40mph+ . Truck feels like it doesn’t mind it, but sounds like it doesn’t like it. There’s an extra noise that comes with cruising at 40mph+ another faint phenomenon that I can actually feel in my steering wheel if I feel for it carefully. It sounds like faint pulsating shuddering. Like a grumbling sensation that pulsates. I can only feel the pulsating part of the grumbling in my steering wheel when I feel for it. It’s hard to explain or know unless you drive it. Mean while I’m hearing that faint grinding noise in the background of the grumbling. The grinding and grumbling all go away after I reach and cruise at 70mph+. All of it sounds like it’s coming from my engine. Or where my engine meets my transmission. I’m in the cabin so it’s hard to pin point the location of the sound. Think it might be my transmission, or engine. But what the hell do I do to look for it? Has anybody had this problem b4? I’ve tried searching similar things but none match up to what I’m experiencing. And clues? Thanks

Topic

[Charles]

I’m guessing that you have a pickup truck of unknown size and manufacturer. May be automatic or manual transmission. Also guess that if the noise is only happening under load and the truck is large enough to have an intermediate shaft, perhaps the intermediate shaft bearing is bad?

[Ryan]

Ha I’m sorry forgot the most important information. It’s a Mazda b3000 and it is a manual drive truck. Are you talking about the drive shaft when you say intermediate shaft? The pinion gear in my differential? Or does a intermediate shaft have to do with steering? If it is steering, I’m almost positive that can’t be it. My steering is great! Nothing funky, no play, and the noise doesn’t alter when I turn the steering wheel. However I noticed when I switch from 4th to 5th, I had the clutch pressed in a little longer than usual to see if the noise goes away. It was still there whether I was in gear or rolling in neutral. I hope it’s not, but I think I read somewhere that it might be my pinion ring and gear. I guess something this complex would have to be looked at by a professional. But most of them down here are crooks!!

[Charles]

If the truck were of large enough stature it might have a two piece drive shaft with a carrier bearing between to two parts. If you suspect the differential and you are game, jack up one rear wheel and support securely with a jack stand. You can then run the drive train under controlled conditions to try and identify the issue. Could just be wheel bearing. If you don’t learn anything with that wheel put it down and jack up the other.

This procedure only works if you have a standard rear differential. Limited slip will require both wheels to be off the ground. Note that with one wheel off the ground the speedometer reads half the speed of the one wheel.

[Kenny]

Check your axles as one of the guys mentioned. They can easily be inspected visually (check boots for grease leaks) or by feeling. Check for play. A little Side to side movement is okay vertical play is a no no.

[Author]

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