My 1988 chevy sport van makes a lot of noise when I drive down the road. It kind of roars from the floor area while driving down the road. Near the transmission area I think.

Of course not! Take a drive shaft off and there is no equilibrium, and also a HUGE puddle of oil as just a big hole. 'Roaring' is normally wheel bearings. Sell it and get a bike!

Needs a good washing under the axle area. Sounds like the mud dried and causing friction

No they don't always do that but I have found that a roaring noise could be from the tires and not the engine.

A jet engine type of noise from the engine area usually means the fan clutch is going bad. I don't think the tach is related to this, that could be the stepper motor for the tach going bad.

bad front wheel hub/bearing

spin the drive shaft back an forth, if it has play then its your universal joints, also lift drive shaft up and down near the the bearing and see if there's play there as well.

3 suggestions for you, you may need to check the tire pressure, get a tire alligment done, or you have a bad wheel bearing, usally a bad wheel bearing make's a loud roaring sound going down the road. I hope I have helped you.

Most likely a wheel bearing issue....if noise goes away when turning....most likely is the bearing....which side is bad is difficult to decide,and they can be pricey...they are bolt in..so not a lot of labor ...good luck...Lee

Either the tires have slippe belts in them, mainly old or worn tires. Or more common is one of your wheel bearings is going bad. Could also be an axle shaft. Jack up the front of the vehicle and grab the wheel and see if you can move it up/down or side to side. see if there is excess play to check wheel bearing issues

have you checked the fan clutch assembly?