Q: Won't drive forward only reverse

Hello...there is a fault in the transmission of course. However, check your transmission fluid level first. If fluid is REALLY low, you could have an issue like this. There is a mechanical linkage in play when you shift into drive. Of course, that should be checked but inasmuch as reverse works, it appears that the linkage is not totally disconnected. If the fluid level and mechanical linkage are good, the next most likely fault is the transmission valve body.

Faults there are not unusual. Valves get stuck because the clearances are so tiny even a speck of dirt can gum things up. Valves can also wear and that will cause shift problems. Hydraulic pressure testing (on car) will identify some of these issues. If by chance, it is just a valve body issue, often that can be repaired without removing the transmission. Beyond the valve body, no or faulty shifting, can be caused by clutch pack failures, missing or torn o-rings and piston leaks and failures (pistons are hydraulically actuated components that operate the clutches).

Although you have a serious issue, there is a silver lining as you are not complaining of an intermittent transmission fault. In other words because the fault is "there" now, it can be found and probably reasonably quickly. Intermittent faults at least require more time and, worse, often "the luck of the draw". Keep in mind, transmission are relatively complex. The wisest repair course will depend not only on what is wrong "at this time" but also in your case the total mileage on the transmission and so you might have to consider the issue of whether a rebuilt will be the best long term solution. For example, you don’t want to spend "x" dollars on a transmission repair this year only to find out next year (if another failure elsewhere in the transmission occurs) that "x" plus another $500 could have gotten you a completely rebuilt transmission. So, the thing to do is get a professional’s opinion that covers all of your options so you can make the decision that is best for you. YourMechanic can get you a diagnosis of the shifting issue and at least an initial repair estimate.