Which is what I've been saying all along, lol. If you ask a question, read and think about all the posts!
Look at your axle tag to be sure. It should be under one of the bolts that holds on the rear cover.
Here's a link to a "decoder" for the information on your axle tag.
Keep in mind you've had a gear change, but the other information is useful.
If your axle tube is 3.25" diameter, it's a 31 spline. The 28 spline is smaller than that.