1999 plymouth voyager has no reverse wont engage, but all forward gears work fine

worn clutch or gear. check shift cable if auto

Your transmission need rebuilding. You can buy some TransX and pour it in your transmission. Make sure drive the car to help the TransX to work it way through the transmission then you should get shift reverse. If it does not work then your transmission is badly damage. So you will have to get it rebuild or buy a used one.

Check your shift selector and see if it is obstructed and not settling into the shift slot

Probably. There may be a solenoid not working which is keeping the transmission from engaging the forward gear train but for it not to work at all is unusual.

Check you transmission fluid, it's not uncommon for the seals to have started leaking after 10 years.

your trans is in limp mode disconnect battery reconnect see if it reoccurs check trabs computer and all sensors

They are full of baloney. Ther's a switch underneath the shift lever that engages when you shiht into reverse. The mechanic probably loosened it when reconnecting the shift linkage to the new tranny.

Thay may have knocked the switch out of position, which would cause the lights to go on in some other gear than reverse. That would be the first thing I check.

Good luck !

Marco

it could be a bad low reverse servo, bad friction materials. if the friction materials are bad in the transmission then the "sun gear" will not be engaged. This is the gear that allows the planetary gearset to move the output shaft in reverse. So you are looking at a servo problem or a transmission rebuild.

sounds like loose connection on the pump, also check fuses too loose connection may have shorted and blew a fuse too

I had the same problem in my 1999 plymouth voyager. Changed both speed sensors it started shifting perfectly.. Now i get a little thump when downshifting from 2nd to first when stoping change the sensors there only about 20 dollars each its 2 of them on the front of transmission..