No, you dont NEED to. Its just a thin layer of undercoating, it doesnt do that much really.

Underlayment will do much more

 

the limited amount of undercoating my car has we're just knocking it off with a needle scaler, it falls right off.

 

If you can a friend that has a steam-pressure washer (Landa), it will make life easy. Without the heat, the pressure washers don't do much.

 

I removed mine with almost zero elbow work. I used a presure washer with "HOT" water. I then por15 the bottom and re did the undercoating(used dynamat undercoat spray). I then did the entire inside of the car with the spray too, followed by using the dynamat sheets all over the bottom of the car. To be honest with you its the best think I ever did for my mustang. The car stays SOOOOOOO much quiter now and also stays warmer. If I had to put a % on how quiet the car is now, I would say 60% more quiet. The trick is a thick smooth coat on the bottom and a thin even coat on the top so you can apply the dynamatsound proofing. The job cost about $200.00 to do. (100 for the dynamat and 75 for the spray.) Yes I used the spray cans.

 

100 bucks for dynamat? got a link?

 

I just finished my driver's side fender and am working on the passenger side now of my '66

I'm using a 3-4" wire wheel with my drill and a wire brush with a metal scraper some too, it's working real well

End result is definitely worth it