My Ford CV 99 taking delay to get speed while putting in D. Gaining about 20 mph it run as normal

Check the transmission fluid. If low top up, if cloudy change it. There may be a head gasket problem or vacuum hose off. Rev it up, shut off check under hood for hissing sound. If a hose is punctured or a vacuum line needs replacing this is the sound you will hear. If gear shift is loose, tighten it, always check linkage under the car. It can cause an accident if not tended to immediately. Diagnostics will tell the problem.

I have changed the complete Transmission.

Another troubleshooting tip would be set up the idling speed to specifications. Takes about 5 minutes on diagnostics to do, should not cost more than $50. The OBD11 device found at car parts stores costs about $200 and really is a money saver. Codes come with it or can be obtained online, anyone who can read can use one and instructions come with it. Linkage might be obstructed. An accident may occur when driving it somewhere. Has absolutely nothing to do with the transmission other than low fluid, check it if the level keeps dropping then it may be a gasket leak. Fords are finnicky in that a simple vacuum hose causes this to occur. Spend $50 and get it looked at. Stops the worry!

thanks Kathleen.. the transmission problem solved. A new problem appears Ignition starts delay and after start it seams the engine is shaking or jerking. One weak before I have changes all plugs. Also there is some mark of water leakage on in take manifold but no water leakage is there. Can you I get some information what to do.