The right rear axle seal on my 1991 Toyota 2wd pickup keeps leaking. I've had it replaced 3 times in the last 7 years and now it needs replacing again. Last time I had it replaced (January 07) I asked the mechanic (Toyota dealership) to see if there's a reason why it keeps blowing. He wrote "no marking or scoring of the hub, all appears to be OK. Suggest for customer to check the differential bleeder at times to make sure it's free so the pressure doesn't blow out the seal". I'll admit, I haven't checked the differential bleeder (I didn't even know it had a bleeder). Besides checking the differential bleeder, is there something else that could be wrong? It costs over $200 every time I get the seal replaced which seems to be every time I have my annual inspection now. I can't do it myself because it requires special tools and a hydraulic press. Thanks for any advice.