Irregular verbs in the future all use the regular the future tense endings, but change the stem. In this category, some -ER and -IR verbs replace the E or I of the stem with a D, and then add the regular endings:
VOWEL -> D | ||
tener | to have | tendr- |
poner | to put | pondr- |
valer | to be worth | valdr- |
salir | to leave | saldr- |
venir | to come | vendr- |