Hi,
I don't know if this will help or not, but....
When my 2004 W-22 went in for the brake recall at our local Workhorse repair shop, they replaced the left front seal as part of the repair. This was in December. Once it came home, I didn't drive the moho again until April, and when I did an inspection, I saw it was leaking. This, after about 100 miles on the seal. I brought it in and they inspected it and the WH Rep told the Manager "Another botched seal.".
Now, I also remember reading at the time this was done that those who replaced the seal with a non-Workhorse replacement, tended to have more problems with leaks. I would think that a WH facility would use only WH parts, but the WH seals were considerably more expensive than the NAPA et al replacements. So, I can't say for sure they used a non-WH seal that time, but it wouldn't surprise me, either. The replacement seal they installed has been good since then (going on maybe 5-6 years, I think). (Yes, I know WH isn't manufacturing the seals, but there apparently was something different about their's compared to the other, cheaper versions, on the market, perhaps reflecting some of the statements made previously in this thread about the types of seals.)
So in addition to the suggestions made by others above, you might want to try using an official Workhorse replacement seal.
Good luck,
~Rick
