Sway bar bushings
Just out of curiousity, how is the transmission in this vehicle. Could the transmission be out of sync with the engine? This has happened to me when i had the transmission replaced in a dodge caravan, Good Luck
Possibly a worn out universal joint.
Year, make, model, engine size, etc. does help. Possible engine mount, u-joint differential,trany, etc...
Are you sure it is the transmission that is clunking? It could be the u-joints on the drive shaft that are making the noise. When the u-joints on the drive shaft are bad, there is an audble clunk when you accelerate and when slowing down (basically the same motions you go through when shifting gears).
When turning the wheel, a clunk means a tie rod or ball joint is worn out.
Worn CVC joint. Could be bad struts causing the spring to bind. Depends how severe the clunk is. If it is struts, it sounds like the floorboard is getting hit by a sledge hammer.
If the gears are clunking in the transmission, this is a transmission problem in a 1998 Dodge Grand Caravan. The fact that the speedometer went up and back down suggests that the transmission slipped. It is more likely that a gear belt in the transmission failed, than something being wrong with the transfer case module or TCM.
You're a clunk-head...
You most likely have a bad universal joint. This universal joint is located in the drive line of the vehicle and needs replaced as soon as possible.
Could be ball joints.Dodge have been known to have premature ball joint failure. Have your front end suspension checked soon. Ball joint failure can lead to entire wheel coming off !! If it is clunking it is pretty close to failing !
Usually it sounds like a clunk. Put the car in drive, step on the brake pedal and hold it down while you slowly accelerate on the gas pedal. If the engine lifts to one side, your mount is broken.