ABS and Brake light come on after driving for a bit.?

Sometimes the ABS light illuminates when your brake fluid is low.

Check to see that your brake fluid isn't low, then take the car to the nearest auto parts store and ask them to pull your computer codes for you.

When you get the codes, go home and search online for any needed cleaning and test procedures that apply to any of the codes you receive.

You must always test, before replacing anything based on the findings of a scanner / code reader.

These devices are very helpful but only report the information as received from the various sensors.

Unfortunately, they are not able to verify whether or not a particular sensor is defective.

This is why you must always test to find the real problem.

GM trucks of that approx vintage are famous for having corroded ABS box ground wire, and also for having cold solder joints in the box failing from vibration -- you tube is full of video on how to adress these. Since your problem started when the larger tires went on, it's likely that larger tires precipitated the issue. You still have brakes, but no ABS.

It sounds like the abs sensor(s) are having a problem with the larger mass turning on the wheel. I've only heard of it happening when people go crazy with rim size, but it's possible with an increase in tire size. But always check the fluid just in case it's that simple.

You need to retrieve the codes and diagnose them.

ABS module failures common on those truck.

There is a service bulletin for the ground for the ABS module for that truck I think, Basically to improve the ground connection (it's a fairly large ground ( 12 or 10 gauge) on the frame beneath the driver more or less.

any time that there is an abs issue, the brake light should come on also. get the brakes inspected and let them know that you are concerned about the abs light.

either the e-brake accuiator or wheel speed sensor, most likely a wheel speed sensor. that means you need a new wheel bearing if your not familiar with car repairs.

Sounds like your brake fluid is low.