Hydro Boost and Rear Disc Brakes

Well if the OP is correct and the parts have the same number across all the platforms it might be the same mechanism.

 

So went through and the part numbers for the Tacoma, 4Runner and Landcruiser brake assemblies all have different part numbers.

 

Your first issue is going to be fluid volume capacity. Discs use a lot more fluid than drums do. So your rear solenoids need to be sized to flow enough fluid or you will have poor response.

Then you need to worry about overall system capacity. Is the accumulator big enough to handle four disc calpiers? Does the rest of the hydraulic circuit have big enough lines? Will the pump overheat from the added duty?

Then after all that you're going to have computer feedback issues. ABS and A-Trac on your truck are tuned for rear drums. The brakes might jitter or lock up because the control solenoids will have a much different effect on your rear discs.

The only way to do it and know that it would work, would be not to take half measures and just swap out every part number that might be different between the pro taco and whatever 4runner has a comparable system.

Alternatively you could be the guinea pig and try swapping a couple components at a time until it works right.

 

This is why I was asking. On the hydro assist braking system (Models with A-Trac) the MC, ABS and traction control systems are all built into one unit, which is why it's not a simple discussion process. If it was a standard MC the Tundra MC is a common swap that works well with big brakes up front and disks in the rear. I'm researching this to get braking out of the front BBK that I have, but I can't simple upgrade the MC or play around with proportioning valves and solenoids.

The 4Runners and Landcruisers have the same hydro assist system, and run both larger front calipers and rear discs. I can across this thread becuase the OP stated that the part numbers are the same, if that was the case then the system in the tacoma will be capable of running them as well. However, I came up with all different part numbers for each. At this point I want to see if they are 1) Interchangeable 2) If specific components are different like the MC and the other comments are the same or 3) can the ecu's be moved around from each one