Wornb brake pads. You are hearing the warning device that is telling you to replace the pads.
It depends on the vehicle and how hard you'll be braking! Basically drum brakes are quite old fashioned and can 'lock' under hard braking or if they get wet. This can cause the wheel in question to skid! Most new vehicles these days unless they are very cheap (usually motorbikes) come with disk brakes. They won't lock if they get wet or under hard braking. Also disk brakes can have an extra feature called ABS - or Anti-lock Braking System - what this means is that when you press the brake pedal the brakes automatically turn on and off a hundred times a second or so - actually allowing you to steer. Very good. Nearly all cars and many motorbikes come with this feature as standard or an option.
Disc brakes generally experience less fade than drum brakes under heavy use. This is because disc brakes have better heat dissipation due to their exposed design, allowing them to cool more effectively. In contrast, drum brakes can trap heat, leading to increased brake fluid temperatures and reduced braking performance. Overall, disc brakes are typically more reliable in preventing fade during prolonged braking situations.
My first guess would be the front end alignment and possibly the brakes. During braking, you engine and transmission are not under a load so they should not cause any vibration.
The brakes are designed to handle that truck at the loaded weight - when under that weight, a bit more finesse needs to be used when braking.
Tighten the belts
Look to the alt. belt. It may squeal under load.
Check the LPV (Load proportioning valve), if fitted. It controls the amount of rear vs front braking under "heavy" loads, if faulty it will cause rear lock up. Another thing to check is that front brakes have been bled, and the front brake circuit is working at all.
Hydraulic brakes were invented to improve the efficiency and effectiveness of braking systems in vehicles. By using hydraulic fluid to transmit force, these brakes allow for greater stopping power with less physical effort compared to traditional mechanical brakes. The hydraulic system also provides more consistent and reliable braking performance, especially under varying conditions. This innovation significantly enhanced vehicle safety and performance, leading to widespread adoption in automobiles and other machinery.
Vented disc brakes have internal channels that allow for better heat dissipation during braking. This design helps to prevent brake fade, which can occur when excessive heat builds up, reducing braking efficiency. The ventilation also improves airflow, allowing for quicker cooling and maintaining optimal braking performance under heavy use. Overall, vented discs enhance safety and reliability in various driving conditions.
I would add overload, and collisions.
if it is automatic then this would be caused by shift down is not working in transmission
Did you check your drive belts. If they are loose they will slip and give off a high pitched sqeal.