I have a 99 contour 2.5 v6 manual transmission. Sometimes while driving the transmission will stop engaging the speedometer will stop telling the speed you are traveling it will go up and down will the rpms. No mater what gear you try forward or backwards it will not engage. If I wait a minute or two everything will go back to normal and I can drive off. The problem is becoming worse happening more often and having to wait longer for it to engage.

 

With a manual trans the vehicle of course has a clutch system. Most had a hydraulic system similar to a brake system. There is a clutch master cyl, line from master to slave cyl that is supposed to release the clutch when the clutch pedal is depressed so the trans can be shifted either into gear or another gear. When full engagement is not permitted either because the clutch parts are worn out or the hydraulic system is preventing full release for the clutch to engage , the result is "clutch slipping". It does sound like some slipping is taking place. The problem is to determine why the clutch will work fine sometimes and not others. Until all the hydraulic parts are checked for correct function , it would not be wise to condemn the clutch assy. The longer you wait to have the problem repaired the more slipping will take place and the clutch parts will then definitely have to be replaced because they will be burned out.
There could be a problem with the hydraulic pressure not being released when the pedal is raised and if there is a hose involved it could have an internal obstruction preventing full pressure release. Now you have some idea of what is supposed to happen you may be able to have it checked out soon!

 

So what would cause the speedometer to act like it is only when the clutch won't engage?