Yeah the issue is the Jeep is weird in this aspect.
The velocity is applied to the humanoid root part and not the actual jeep model. I talked about it here in this post.
I suggest using another vehicle to do the job. I suggest this constraint chassis because it’s simple, works good, and really modifiable and understandable. Though I dislike certain unoptimized aspects of it but that can be easily changed as it’s not loaded with too much features like A chassis.
However, I suggest increasing the friction of the wheels or else it’ll have no grip and can’t climb up slopes, and yeah that’s it, a friction value of one should do.