Power brake booster gvw question

[Ky85]

Looking at power brake boosters online, they are designated as over/under gvw 8500 lbs. This creates some questions;

What is the difference, if any, in using one that says 'over 8500 lbs' on a truck that weighs 5680?

If I had one that was under 8500 and then went over that weight, how bad would the breaks get?

Thanks

 

[ifrythings]

Generally the under 8500# gets the smaller booster and over 8500# gets the bigger booster, you can put the bigger one on a truck that had the smaller one and get more brake pressure, good when towing a heavy load.

Over 8500#

You must be registered for see images attach

Under 8500#

You must be registered for see images attach

Edit: all idi trucks will be over 8500-9000# depending on cab configuration and 2wd/4x4.
Your door sticker will tell you your GVW

 

[Ky85]

Thank you!