My '93 Vette is having brake problems. The pads are OK, the lines have been bled, fluid is OK, but I'm not getting good braking at the rear.

If I stand on the brakes sitting still, the front end holds, but the rear tires start spinning. There's not enough braking power to engage the ABS even if I try a panic stop. I don't think it's the calipers, because both rear wheels break loose.

At 135,000 miles, I'm guessing the master cylinder is gone, but at the price they charge for 'Vette parts, I'd like a little more info before I drop big $$.

Any ideas?