Hard brake pedal when going fast off road

[tooltime]

My little ST is getting quicker with every mod. Been off road pre-running many years at sometimes high rates of speed. When driving with an automatic Transmission, I often drive using the two foot method in order to make the truck do what I want it to do.
Recently, I have noticed a hard brake pedal after being on hard throttle, lifting for a quick second, then setting up with the brake and going back to throttle to help lift the nose and plant the rear. I can get my pedal back by completely lifting off the gas and brake for a quick second or two. Then its business as usual, until the next corner or set of rollers. The problem is, this issue has caused me some close calls.
I briefly sprayed throttle body cleaner around most of the vac lines, and did not notice any change.
Any ideas out there? :scratch:

 

[russelltcampbell]

sounds like abs doing its job.

 

[05dakotatrac]

typically pre-runners, nascar, and most other "race car" applications remove ABS to allow lockup and in a sense drift the vehicle using brakes. honestly locked brakes on open dry roads stop quicker then ABS but at a downfall you loose control over the skid.

honestly i have driven cars with no abs, only rear abs (dumba** GM 2500), and full abs the one that stopped the fastest was no ABS in almost all conditions besides snow and ice. the one that had most control in all conditions was the full ABS.

and on a mechanical note if you dont feel a "pulse" under your foot its probably not ABS. hard pedal is a sign of vacuum loss at the brake booster. just cause your vacuum hose spray down came up empty it is still possible the guts of the booster are shot.

 

[roamer37]

At WOT there is no Manifold Vacuum to speak of you need some sort of vacuum pump be it electric or engine driven like most diesels.

 

[tooltime]

Russell, and Dakota thanks for your replies. I do not remove the abs relays, fuses ect. I know for sure my issue is not the abs. I have been a professional driving coach in many types of vehicles for 20years. Driving fast in anything with abs takes some getting use to. We would spend a lot of time with students getting them to know, understand, and use the abs correctly. I have no problem with or without.
Now Roamer, you are on to something. You have confirmed what I was thinking. I need to look into what I have tinkered with to change the vacuum in the system. I need to think back to when I first noticed the issue and start there. Thanks Roamer.