
Is going to the surgeon the only time he's in the car? If so he'll have unpleasant associations with it. Mine hated the car so here are some of the things I did.
Feed his dinner in the car without going anywhere.
We stored his special treats in the car. So I'd get excited, 'want a pig ear, ooh let's go get a sweety'. Take him out to the car, let him jump in, get the treat and get out again.
Jump in the car, have a treat, then go for a walk
When he can get in without being too stressed turn the engine on but don't go anywhere. Give him his dinner/treat then let him out.
When he's OK with that take lots of short trips to fun places
You get the idea. Make the car a good place where he gets nice treats and car rides mean fun walks. BTW - if your crate is not made specifically for cars then the rattling could really upset him.