Okay..........
here's what it looked like with the aluminum backing plates:
Please note how deep the splines go in relation to where the slinger will sit and the "lip" on the blue seal......That's your problem...
Here's a pic with the slinger on.....I could just push the slinger on and past the blue seal with no problem...it's not a correct fit. That's where it leaks...and it leaks like a sieve.
Now notice how everything works when installed "correctly" - no more leakage....
If it was as easy as slapping the aluminum backing plates on these axles and bolting everything together and it all worked right - MBT wouldn't be making repro backing plates and we wouldn't be searching every Porsche breaker in the country for these steel ones.
Dan