Gudday Infantryman,
A simple question.....have you got;
A; Drum brakes all round.
B; Discs at the front, drums at the rear.
C; Four wheel disc brakes fitted.
It is possible that someone without the appropriate knowledge may have fitted the wrong type of master cylinder to your Truck.
A drum brake system will have a residual pressure valve fitted in relation to stock 4 wheel drum systems.
If a disc braked front end has been fitted without the residual pressure valve being removed from your master cylinder, your brakes WILL lock up after a very short drive.
The same applies to a 4 wheel disc set-up running the drum brake equipped master cylinder.
It is easy to find and remove the residual valve yourself.......but you do need at least a simple understanding of mechanical knowledge to do so.
Take it to a brake expert, explain the problem and mention the residual pressure valve.
They might think you know what you are talking about and not rip you off too much!!!!!!!!!!!!!!
All the best, Doc Bob