The D21 has huge rear brakes but the R/V's are built on the 1 ton chassis but it has huge rear brakes as well. I owned a 1995 D21 and it had rear Anti-Lock brakes. You might want to investigate that. The ABS module is under the drivers seat.
I would be checking if the rear brake proportioning valve is adjusted correctly (if it even has one) and working properly. With an R/V permanently mounted on the Pickup the chassis is fully loaded so you could remove it altogether.
I would also check if the brake booster is working at all, sometimes the booster check valve gets clogged up and you have no power brakes. To test the booster operation: step on the brake pedal and then start the engine, the pedal should drop slightly, maybe half an inch. If it does not drop once the engine is started the booster is not working.
Has anyone actually taken off the rear brake drums and looked at the the brakes?
Don't overlook the possibility that IF the rear brake cylinders are seized up (rusted up) you would have no rear brakes, same goes for the front calipers if they are seized up (rusted up).
You should be able to lock up all 6 tires with the Nissan brake system. I have done it. They are very good.
Aaron from Colorado
