Anybody have a 90-91 Sub/Blazer with working ABS?

[Zoomad75]

It's one of the first ABS systems GM used. Zero parts availability to replace the pump/module assembly.

Plus the system is only functional to the rear wheels which won't help with directional stability if the front wheels still have the possibility to lock up.

Chances of getting a good used one is pretty slim since it's been 30 years since they came out. Also the GMT400 rear ABS system is different so it's not a possibility to retrofit to the earlier platform.

When attempting to bleed my '91 during the intial LS swap we ran into a major issue where we could not get fluid to flow to the rear circuit. We followed the service manual procedure with a fabricated bracket holding the plunger down on the proportioning valve, still wouldn't flow. We tried everything, the system would not push fluid to the rear.

I ended up pulling a proportioning valve and the lines between it and the master cylinder from an earlier non-abs truck. Swapped them in and rears bled just fine with the same master cylinder on it. You do have to change the tube nut on the rear line to match the fitting in the prop-valve, but there is just enough on the stock rear line to cut the line, take the nut off and re-flare with the correct fitting on the line.

I haven't been in a situation where I felt the Rear wheel abs would have helped better.