I've been unable to find answeres on the internet. Hoping someone here can help me out.

85 4runner

During, or after it rains, sometimes on dusty trails, when I apply the brake hard, I get a really loud grind that shakes the whole truck. It happens in neutral, it happens in drive. If im driving slow enough, instead of grinding, the truck will jerk to stop. If it is not raining, the problem disapears, and I can hard brake just fine.

 

Have you taken the wheels off and taken a look at the brakes?

Sometimes a good visual inspection will reveal your problem.

 

Yes^^^ our senses (see, hear, smell, feel - don't know about taste with the truck - LOL) are the most important troubleshooting tools.

 

Water washing grease etc onto brake material

A few applications cleans it off till the next rain

 

What he said, but I don't recommend tasting any part of the braking system.

 

Yum! Tastes like toxic road grime and grease, maybe brake pad material and brake fluid too!

Yeah, that sense is best left to food.