[HotWheelsFan]

Forward clutch assembly should engage when gear selector is in low, second, and drive. If the seals have hardened the fluid will bypass the seal preventing the clutch pack to engage. Vehicle will not move forward without this clutch pack engaging.

Problem may also be low fluid level, low internal fluid pressure, broken part, or other...

If you feel the shift detents while moving the gear selector from park to low, in each gear and recheck the fluid, you could try add a transmission conditioner that reconditions seals. The seals that apply the clutch packs work similar to the seals in brake wheel cylinders and master cylinder. When pressure is applied, the seal will expand outward to seal against the outer bore that the seal rides in and thus builds pressure in the system. If the seal becomes less pliable, it will not expand and instead of the system building pressure where needed it allows the fluid to leak between the seal and outer bore that the seal sits in.

A trans fluid conditioner can soften seals so they can expand when needed. How stiff seals can get when not being used for extended periods of time is like comparing rubber in cold weather and how stiff it gets to how rubber feels when warm. Just like a garden hose may get real stiff on cold winter mornings compared to using the same hose during the summer.

If you follow the directions of a bottle or two of conditioner, run the fluid through the trans, warm up the vehicle and trans, may take a few days for the conditioner to sit in the trans... This may help, and if it does work, regular use of the transmission for a few days could get the seals back in shape.

You don't want to run the trans if you hear noise from it, you don't want to force the trans in any way such as trying to get it to roll forward if the gears are slipping. If the trans does not work and needs to be disassembled for repair, forcing things will only cause more damage and add to the cost of an overhaul by damaging parts that do not come in an overhaul kit.

Bob