Good luck with your repair.
I have the a 1997 pickup with a nearly identical configuration. No easy answers although the suggestions upthread are good ones.
You should replace the rear wheel cylinders if you have not already done so. You should also replace the hardware kit and self-adjusting screws for the rear if this was not done. This vehicle has a parking brake that uses a cable setup to apply the rear brakes. It is common for the cable assemblies to corrode and stick, and they should be replaced if there are any signs of sticking.
There can be a slight pull to one side if one of the drums is worn almost to its service limit and the other is near new. If that is your situation or even if the drums are just badly worn it might be best to replace them.
You would also want to check visually for a kink, crimp, or other damage in the metal brake line that runs along the rear axle.
You may find the folks over at gmtruckclub.com to be more helpful since Chevrolet suburbans are one of the vehicles they focus on.
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