Ok so this just started. When the truck is under load and I'm heavy into the throttle I get a howl, and a vibration, it sounds almost harmonic. As soon as I let go of the throttle it stops. I checked my torque on my tires just to be sure I wasn't about to lose one (been there done that). So now what should I start looking at.

1993 f350 idit
Zf5
Dually

 

Other than the vibration part (check Ujoints and driveshaft carrier brg), without hearing it first hand, a howl is most often a rear end going out.

 

I'll make a video tomorrow of the sound when I head back to work and upload it to YouTube. Sounds like it's coming from the front of the drive train. I just had tires put on and an inspection done but I have been beating it up and down a pipeline row for a month. No play in the steering wheel and truck tracks straight.

Thanks for any suggestions

 

Oh not sure if it's worth noting but the sounds stops at 120kmh 75mph and it's a low intensity sound that increases with rpm through every gear.

 

Load dependent and near the front, my guess would be transmission. But, noises can appear to come from one area and actually be from another. Check the trans fluid level and condition.

I have one of these I can 'rent' to you for the cost of shipping. Or poke around Ebay and find one cheap, they're pretty cool. It should let you pin point the noise.

 

Doesn't sound like a bad rear end then. A differential howl will be at a certain highway speed then you can make it come and go by floating back and forth with the throttle, drive or coast.

 

If it was transmission what would cause it to howl in every gear but only under full throttle and immediately stop when the throttle is released?

 

Impossible to diagnose a trans (or rear end for that matter) by sound. I've torn a few not too noisy ones down and every internal component was scored beyond use. Other noisy ones got by with just bearing replacements. Generally if it is noisy the longer you drive it the more damage you do. Metal chips or flakes from whatever is failing soon score other gears and/or shafts. Trans gears and shafts are REALLY expensive.

 

If it was me I'd pull the driveshaft and replace u-joints and if applicable the carrier bearing.

I've seen some weird stuff and noises from u-joints. I had one that only made noise when taking off/letting the clutch out. My current truck vibrates with high throttle in 1-3 gears due to the carrier bearing. When you're getting on it the engine moves and changes things.

 

Well it's getting driven until it either blows up or I figure out what it is lol. Worst case I detonate something and have to rent a truck and start my 4x4 conversion.

I'll still post up that video.

 

Any problem with the input shaft. I'm not a trans expert so I can't tell you exactly which part, but my guess would be an input shaft thrust bearing/bushing starting to go.

 

Was just going to say this, or transfer case.

 

There is no transfer case it's a two wheel drive. I'm hoping to get it in a garage tomorrow after work so I can take a look at it. If it's a u joint it should be pretty apparent and that's easy enough to swap out. I'm not sure if there is a way to diagnose an input shaft without pulling the transmission but if it is an input shaft I'll have to cross my fingers and hope it can handle another 6 weeks of pipeline. I also had a suggestion to check my exhaust connections.

I'm not feeling any abnormal vibrations come through the shifter.

The truck will be getting converted to a 4x4 after this job so hopefully whatever it is, is minor.

Thanks for all the input guys.

 

A ZF 5 spd doesn't have an input shaft thrust bearing or bushing. Can't think of a manual truck trans that does.

 

Shows how much I know about transmissions haha. Thanks one less thing to try to track down.