Brake Light On

`91 C1500 w/350

When I hit 35 mph my brake light pops on, when I hit the brakes the truck pulls to the right, and the cruise control no longer works, but the brake pedal is still firm.

Any suggestions on what might me wrong?

I'd suspect a problem with the VSS or buffer. The ABS system uses vehicle speed data generated by the VSS to compare the wheel sensor data and determine wheel slippage. Data from teh VSS is also used as the reference input for the cruise control, as well as the ECM and speedometer.

The brake pulling to the right could be related, or may be a separate problem. That would indicate loss of braking force on the left side, either due to friction material contamination or wear, or possibly sticking brake hardware (caliper, wheel cylinder, etc.).

I don't have ABS, but would I still have a VSS or buffer

you might want to check your front brake lines for the pulling problem. The rubber lines have a tendency to collapse internally and cause pulling. I have had to replace both of mine on 93 4wd.

If your truck has a proportioning valve that could be what's turning the brake light on. Check the fluid in the master cylinder. Check all wheels for leaks. When you hit the brakes the cruise is supposed to disengage.