Deleting transients in custom post types

I want to know if exists some hook or function to delete a transient for a custom post type. I need to delete the transient and create it again, always I publish new post or update a new post. My code till now is:
if ( false === ($ultimas_publicaciones = get_transient( 'ultimas_pub' ) ) ) {
$args = array(
'post_type' => 'publicaciones',
'post_status' => 'publish',
'post_per_page' => 3
);
$ultimas_publicaciones = new WP_Query( $args ); ?>
<?php set_transient('ultimas_pub', $ultimas_publicaciones, 4 * WEEK_IN_SECONDS);

function cambiar_transient() {
global $post;
if ($post->post_type == 'publicaciones') {
delete_transient('ultimas_pub');
}}
add_action('save_post', 'cambiar_transient');

So, I don't know if the problem is in the last sentece or wherever, because the transient works great! but I need to regenerate it when I publish a new post or update a post.
Custom post type: 'publicaciones'

Thanks in advance!