96 toyota stock 4runner 2 wheel drive

It's leaking diff. fluid into rear left brake drum and I replaced the seals. What else?

Check to see if the vent is plugged/kinked etc. If it is, the differential is building up pressure as it warms up and pushing fluid out the seals.

I remember some sort of problem with 4Runner rear axles around 96-98 or so, that caused leakage. Something about wear on the axle shaft causing a poor seal and/or tweaked housings.
You may want to do some research.