Question

What is the major product formed in the following reaction?

Answer is, there is Br in place of OH. Why there is no Hydride shift?

Answer 1

Consider the SN2 mechanism of your reaction,

Recall that SN2 is a concerted substitution reaction, so a carbocation intermediate is generally nonexistent.

Even if somehow there was a hydride shift, the reaction would yield nearly none of the tertiary alkyl product because there is far too much steric hindrance/electronic repulsion/molecular orbital misalignment for the nucleophile to attack effectively.

If this reaction underwent an SN1 mechanism, you would need to do a hydride shift, though.