What caused my Rear Axle Seal to go? Synthetic Diff Oil?

I took my truck off-island yesterday to get it aligned after my OME lift. I just arrived from Alaska, where I carried FAR too much weight... Preliminary inspection after I took the weight off the truck showed that I didn't blow out the rear axle seals. That was 1000 miles ago. The truck was fine until I took it up to highway speeds. (nothing faster than 45mph where I live).

About 6000 miles ago, I switched out my fluids, including the rear differential fluid to synthetics. At the same time I put on a rear differential breather hose for me... Garden Hose and clamp...

And yesterday, when I got the truck up to 70 mph for the first time in... goodness...at least 5000 miles, my left rear axle seals gives out, soaking my break shoes in the process. Dang.

After using the search feature, I've learned that they can go out for a variety of reasons...

1. Worn out wheel bearings
2. plugged rear diff breather
3. And now this: a Tundra TSB: DL003-03 that says that 2000-2003 Tundras/Sequoias have a seal design that causes it to go if you use synthetic oil.

Could that apply to my '98 Tacoma? How long would it take for the wrong chemistry to cause a seal to fail?

Question: can I get away with doing only the left (blown) side? How will I know if the bearings are shot?

This never comes at an easy time, does it? I gotta load the thing back up with 2000 lbs and head back to Alaska in a week to teach... grrrrrr....

 

Unless you put some wierd acid laced diff fluid there is no way oil will cause your seal to fail. So it was not fluid that did that.
Either it was its time to fail or your bearing is dead and after you loaded truck seal could not cope anymore.
Yes you can change only one side but since you need to do all that work you may as well just replace both of them.

 

It turns out that TSB DL003-03 *does apply*. Copied from another site (Tundra Solutions:

Hmmm.... does anyone have any experience with this?

 

Marlin Crawler has HD axle seals
http://www.marlincrawler.com/axle/rear-axle-parts