Reddit mentions of FloTool 05034MI Extra Large Funnel

The 1999 TL had the 4 speed automatic. Do NOT do a flush, it will ruin this type of gearbox, there is a MUCH better, more delicate, correct method.

These gearboxes are notorious for shifting hard when the friction modifiers in the gearbox fluid have worn/failed. The fluid requires a 30K change interval once the car has over 60K miles.

I will bet you $100, if you follow this procedure the gearbox will shift like brand new again, assuming the clutches aren't already lunched (which if its not slipping they probably are fine).

Go to Amazon, and get 6 quarts of DW-1. This is Honda's newer revised gearbox oil. Don't get auto parts store stuff, it won't have the correct additives for Honda's type of clutches.

go to your local auto parts store, get a drain pan, and a 3/8inch ratchet, along with a funnel and that has a long fill tube.

Get the car up on ramps and remove the gearbox drain plug, what will drain out is some extremely dark looking ATF, roughly 3 quarts worth.

Once drained, refill the gearbox (through the dipstick hole) with 3 quarts of the DW-1. Take the car on a short, slightly spirited drive. You will already notice a night and day difference in gearbox behavior, however, it won't be perfect. This is because you only drained about 3/4 of the fluid in the gearbox, and what is happening is the left over old fluid that was in the torque converter will be mixing with the new fluid.

After 10-20 miles everything should be mixed around pretty good, put the car on the ramps, rinse and repeat. Drain the gearbox, the fluid should look a little bit darker than it was before you poured it in, this is good.

Once drained again, refill with the remaining 2ish+ quarts (Add two and top up with the third) and button everything up. Also, the gearbox plug has a magnet on the inside end, inspect for solid chunks or pieces, there may be a little bit of a sludge on the end, this is okay, clean it off and reinstall it.

Your gearbox will shift butter smooth, its not uncommon for honda 4 speeds to shift a little bit abruptly at low speed, but overall it should feel much better than it did.

If you keep driving it as is, eventually the clutch packs will fail and the gearbox will need a rebuild.

If anything, if the gearbox is too far gone you spent ~$50 finding out it was terminal, which is relatively speaking a drop in the pond.