The vin only includes engine size, manufacturing plant, model year, and things like that. It doesn't tell which options are on the truck. Only Chrysler has a record of the options it had when it left the factory. Carfax might be using the Chrysler web site to get that information. Rear wheel anti-lock first showed up on '89 models so they wouldn't have been real common yet. You will have a yellow rectangular "RWAL" light on the dash that turns on for seven seconds every time you turn on the ignition switch if you have that option. If the hydraulic control unit is shorted, the system won't work. That will leave you with the base brakes which will perform normally.
"Shot" doesn't mean anything. What are the symptoms? Are they leaking? Is the brake pedal too low and mushy? Do the rear brakes lock up easily? Why does your mechanic want to replace them?
Can you see how many steel lines go into the front valve assembly? If it's a brass block, about 4" long and 3/4" wide with five lines, that is the combination valve. In 28 years of doing brakes, I only replaced one for seeping brake fluid. That was on a Cadillac. That's why it seems strange yours needs to be replaced.
I can't find any reference in the service manual about a height-sensing proportioning valve on the trucks. My '88 Grand Caravan has one so I know they were in use by '89. They are used on pickup trucks and minivans because there can be such a huge change in weight distribution depending on how it is loaded, so they can't design a "one-size-fits-all proportioning valve to build into the combination valve. Can you describe the box you're referring to? Color, shape, dimensions, location, number of steel lines, etc. Can you see it from underneath without removing the wheels? I can't think of any other brake part that would look like a box.
Sunday, May 2nd, 2010 AT 8:15 PM