Help diagnosing driveline noise

Ian Mills · February 9, 2021

My truck had a bad front wheel bearing so I replaced both front hubs with moog units. The noise went mostly away but I still have a rotational chirping noise that happens under coasting and braking but not accelerating. I found excessive play in my passenger front axle (same side as the bad bearing) so I replaced both front axles with new (not remanufactured) parts but the noise is still present. I lifted the truck up and put the transfer case in neutral and I couldn't find and play in the universal joints or the diff. The differential has some weeping seals but it's not out of fluid or anything. The noise doesn't seem super affected by turning left or right. There's also sometimes a vibration that goes with the noise and I feel it in the floor and the pedals but that is not consistently present. I'm kindof stumped. Ideas?

Sharpz · February 9, 2021

3 hours ago, Ian Mills said:

My truck had a bad front wheel bearing so I replaced both front hubs with moog units. The noise went mostly away but I still have a rotational chirping noise that happens under coasting and braking but not accelerating. I found excessive play in my passenger front axle (same side as the bad bearing) so I replaced both front axles with new (not remanufactured) parts but the noise is still present. I lifted the truck up and put the transfer case in neutral and I couldn't find and play in the universal joints or the diff. The differential has some weeping seals but it's not out of fluid or anything. The noise doesn't seem super affected by turning left or right. There's also sometimes a vibration that goes with the noise and I feel it in the floor and the pedals but that is not consistently present. I'm kindof stumped. Ideas?

If I remember from your other posts you are from alaska, I dont know if they use salt there but I would imagine they do. 1st when you took your front apart to change the bearings your rotors could have had rust on them. Some times its inside and you dont see it. If this is put back on without a proper cleaning, when you apply your brakes that rust gets wedged between the pads and rotor and it creates a sort of glazing effect, and you will get a very slight vibration as well as poorer breaking ability. Since the pads are the next cheapest thing to replace, I would replace them and have your rotors turned, or replaced. If you installed the axles correctly and torqued your bearings properly you would have eliminated all possible issues with your front end. From there it would be in your transfer case or transmission. Of course the vibration might just be crude on your rim, or a tire out of balance, but that noise would come from that.

Ian Mills · February 10, 2021

I am from Alaska. When I did the hubs I also did all new front brakes with Bosch rotors and good pads. It's possible that something went wrong with that but I was thinking that the noise would change when the brakes are applied if that was the culprit. The transmission is also brand new from a reputable shop. The noise only goes away under acceleration. I hope it's not the transfer case.

Sharpz · February 10, 2021

39 minutes ago, Ian Mills said:

I am from Alaska. When I did the hubs I also did all new front brakes with Bosch rotors and good pads. It's possible that something went wrong with that but I was thinking that the noise would change when the brakes are applied if that was the culprit. The transmission is also brand new from a reputable shop. The noise only goes away under acceleration. I hope it's not the transfer case.

yeah that would suck. From what you have replaced already I am guessing you keep up with oil changes and fluid levels for that sort of thing but you really have narrowed down what the noise possible things could be.

Ian Mills · February 24, 2021

Just for future reference: I decided to replace the fluids on my differentials and transfer case even though they weren't "expired" and the results are somewhat illuminating. The rear diff was 10/10, the fluid in the transfer case was a bit dark but alright, but I went to do the front fluid and poof: aerated fluid with ice and water chunks. Don't know when or how that happened but that's probably the source of the noise I'm thinking. New fluid and the noise is quieter but still there. I'm now expecting to do a rebuild on that soonish.

Side note: how much lateral deflection is normal on the rear output shaft of the transfer case? I was testing the universal joints (all good) and I found that I could move the aforementioned shaft more than I expected.