when ever it rains and i have my wipers on they slap the bottom really hard when going down. is that just a need of adjusting?

Maybe your wiper arm might be bent? Mine clunked when turned off because they were bent

I assume that the rest of the wiper actions are normal and your only concern is they park themselves with a "THUNK!!!. My 89 Le Sabre did this and my '91 Royale does it too so I think what your describing is normal. The blades are hitting the runbber stops at the base of the windsheild. BTW, the former engineers at Oldsmobile designed in a bolt at the base of the metal plate below the windsheild that was in the direct path of my left wiper when it parked. Needless to say it cut the middle of the rubber blade so I had an arc on the windsheild that would never get wiped. Suffice to say I removed that bolt before I replaced that blade.

the drivers side wiper once in a while goes almost to far and when it goes back down they just go full speed and hit the rubber stop and they hit real hard.

That does not sound right to me. If I have time when I get home from work I'll look to see if there is a trouble shooting guide in my manual about the wiper operation. I believe that when you turn the wipers to the off position on the stalk, it goes into a Park mode where it brings the wipers to rest under the cowl slowly. I'm sure the some of the other members might be abke to help you out on this.

when their on like while its raining they just go all the way down but they dont slow down the just hit the stoppers does that help?

Yeah, but I didn't have time last night to check my manual and tonight I'm leaving for a two week vacation. So at this time I don't know if your problem is electrical or mechanical in nature. I do think that whatever it is will have to be checked out within the wiper motor assembly.

ok thanx

If they are wiping all the way and still hitting the stops, is sounds like the wiper motor might be stuck or jammed in "park" mode. Do they try going even further when you shut them off?

it only happens once in awhile