A loud B74.2D

[Scojo]

Recently got back into RC after a 20 year absence. Purchased an associated B 74.2 D. With hobby wing 8.5 motor, spectrum DX 5C transmitter and 6100 receiver. Hobby wing. Xerun pro 10 ESC. my question is…when on power it is very loud, which is something I haven’t experienced in the past. It doesn’t sound like an incorrect gear mesh which I have checked. It’s more like an electronic sound. Anyone with an explanation?

 

[DavidB1126]

I have a B74.1D with a Hobbywing 13.5 spec motor.
Can you send a video? Most likely motor, but if it's new it shouldn't be loud like that.

I notice that my car gets louder / higher pitched if you put thicker center diff oil in. And it sounds very quiet with a slipper.

This video is me racing .1. Mine seems like the loudest (blue / silver / burgundy body with white wheels)

And this is my uncle's XB4 with a Hobbywing 6.5 and a center slipper

 

[bill_delong]

I would do a complete rebuild, inspect for worn/seized bearings that need to be replaced, including the bearings inside the motor. Also inspect any worn/cracked parts that may have melted/damaged from a bearing failure.

I don't like to buy used cars unless I trust the seller, no telling what's wrong and only way to diagnose is to start replacing things by trial and error, I tend to replace my motors every 6 months to a year as a consumable.

Good Luck!

 

[Scojo]

I have a B74.1D with a Hobbywing 13.5 spec motor.
Can you send a video? Most likely motor, but if it's new it shouldn't be loud like that.

I notice that my car gets louder / higher pitched if you put thicker center diff oil in. And it sounds very quiet with a slipper.

This video is me racing .1. Mine seems like the loudest (blue / silver / burgundy body with white wheels)

And this is my uncle's XB4 with a Hobbywing 6.5 and a center slipper

Thanks for your response! Your Uncles XB4 sounds more like mine. Right when he lets off the throttle I hear an extra echo-ish sound, if that makes sense? It’s similar to what I’m hearing with mine! I’m not running a slipper. I’m running the center diff!

Thanks for your response! Your Uncles XB4 sounds more like mine. Right when he lets off the throttle I hear an extra echo-ish sound, if that makes sense? It’s similar to what I’m hearing with mine! I’m not running a slipper. I’m running the center diff!

By the way, I was running 200K center diff fluid, per kit setup, but about to change to much lower due to running on a loose dirt track!

 

[DavidB1126]

Thanks for your response! Your Uncles XB4 sounds more like mine. Right when he lets off the throttle I hear an extra echo-ish sound, if that makes sense? It’s similar to what I’m hearing with mine! I’m not running a slipper. I’m running the center diff!

Hmm. Are you talking about the motor beeping when you tap the brakes? If so that's normal.for modern Hobbywing motors, and motors in general.
If not maybe I'm not hearing it

 

[Scojo]

Hmm. Are you talking about the motor beeping when you tap the brakes? If so that's normal.for modern Hobbywing motors, and motors in general.
If not maybe I'm not hearing it

I think maybe that’s what it is? It seems to do it when I let off the gas as well. Maybe have a bit too much drag break dialed in!?

 

[WickedFog]

Hmm. Are you talking about the motor beeping when you tap the brakes? If so that's normal.for modern Hobbywing motors, and motors in general.
If not maybe I'm not hearing it

Wondering the same thing. Maybe the original owner has the brake power turned up a bit high. Motors have that audible tone thing going on. Similar to 3d printer stepper motors, which produces an audible tone. You can even use gcode to make them play music at the end of a print, and some tones are much louder than others.

I think maybe that’s what it is? It seems to do it when I let off the gas as well. Maybe have a bit too much drag break dialed in!?

Yeah, quite possibly.

 

[DavidB1126]