URL redirect not working

I moved my URL from http://mywebsite.com/wordpress to http://wordpress.mywebsite.com.

The site works fine in all browsers.

However, I’m loosing rank because my old permalinks are generating 404 errors.

WordPress is installed in a subdirectory. The basic htaccess file resides in the root.

I also have another htaccess file that is in the root of my website.

when I enter

http://mywebsite.com/wordpress

I get a 404 error and a comment that the browser is looking for

http://wordpress.mywebsite.com/wordpress/

This looks like a combination of the old and new URL.

If I try an old URL:

mywebsite.com/wordpress/category/post/

I get a 404 error.

Seems like this would be a simple fix, but I am lost. I have also tried redirect plugins that do work for the domain change (mysite.com/wordpress to wordpress.mysite.com) but not for redirecting post.

Here is the htaccess file in the wordpress root:

# BEGIN WordPress
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteRule ^index\.php$ – [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

# END WordPress

My website root htaccess is a simple redirect command that works for my other site pages just not wordpress:

RewriteEngine On
RewriteBase /
Redirect mywebsite.com/wordpress/category/post/ http://wordpress.mywebsite.com/category/post/