Regarding part numbers, what I use is consulting this site (https://nemigaparts.com/cat_spares/epc/chevrolet/54s-t/) and then double checking against a GM parts seller like GM Parts Giant or GM Parts Warehouse. The GM sites will often allow you to search by using our VIN which is really nice to making sure you the listing of parts for the RPO codes on your vehicle. The downside of the GM sites is that they don't always have the best or any exploded diagrams. Tasca I've learned is more likely to have actual pictures of their parts, even if discontinued.

To answer your specific question, I think the correct part number for part labeled #20 is 26036438. I used one of the front axle exploded diagrams at the nemigaparts and then put the part number into the GM Parts Giant page. This part number came back as fitting my 1999 Blazer with the name "Seal, Front Drive Axle Clutch Fork."

 

Christine: I have not heard of nemigaparts.com nor ever went to their site......now I have it bookmarked!! What a great resource it is.
I agree that the part number you listed above is the seal my Blazer needs.....went to GM Part Giant and it is indeed available. YEAH!!!
Have to say that all I keep thinking about was that I was going to have to seal-off the actuator and disable the front axle engagement so I could still be able to drive the Blazer. Now I can get the new seal.....YEAH!!!

Thank you once again "Christine to the rescue",

LannyL81

 

You are very welcome!!!

 

I ordered and received the new shifter seal; thought I would order a set of the thrust washers as shipping cost was the same.
New thrust washers are the same thickness but the two smaller ones that have the three raised areas.....they are not raised as much as the OEM ones. The large washers with the notches/teeth were exactly the same, as shown above there are two of them in the kit....which I have no idea why. They are exactly the same. The diagram above does not show one used on the left side....???
Anyways the oil seal is out, new seal in, applied gear oil RTV to the right axle tube, bolted everything back in place. Let it set-up for 20 hrs, then began putting gear oil into the front diff without the right CV axle in place. Wanted to see if I had taken care of the leak....so far so good. Will put everything back together this afternoon if all stays good. I still have to replace the U-joint on the front driveshaft sometime in the future.
Hopefully this is the last time I am ever going this job.....

 

Just to finish this thread:
Everything is back together and have taken on several drives with no leaks....so that is good!!
One odd thing is that I expected to have a Check Engine lite come on due to replacing the front cover which moved the crankshaft position sensor, but no CEL yet anyways.
So nice not to have to have a drip pan under the Blazer any longer.
See ya....

 

Congrats and thanks for the update!