2003 Chevrolet S10 Question: Why would I have 2 different size rear axle seals in my 03 Chevy s10 zr5?

I have done that and every seal That I have put in it leaks within a week. The last one that I put in matched and fit perfect and started to leak within 12 hrs just sitting in the drive way.

New axle, bearing and seal should fix this problem. Have NEVER seen in my many years of mechanicing a Chevy. with 2 different size axles!! Unless one had been installed by mistake! If the seals are different size then so must be the axles. No way IF factory. May need a complete differential. Was the seal leaking when you bought the truck?

No the seal wasn't leaking. the axles are the same just the housing the seal goes in. I have had it to the local Chevy garage and they said they have never seen anything like it and couldn't figure it out.

Do you still have the old seal that came with the truck when you bought it? If so see if you see a number on it! Can get another like it. Dont kknow what the deal is but it aint stock.

I have went over that seal with a fine tooth comb and cant find a number.

A GOOD parts man can measure the old seal with a micrometer outside--inside and thickness to find this part for you!! If i had it in my hand could have the RIGHT one by lunch.
But GOOD parts people are getting hard to find, i am old school and used to a parts man taking just as much time on a 6.00 dollar seal as a 2600. dollar engine but them days are gone, sadly, as well as knowledgeable parts people who know how to do this. May have to do it yourself.
Also measure the axle where seal runs and the axle tube inside where seal sits. Stuff on the net to download, google 'oil seal by dimesions' to find a match. Chicago rawhide, Timken, National oil seal, Victor seals and gaskets are just a few places to check but just google it first. You will find it.
GOOD LUCK!