Kia Sedona Software Update Available to Correct Transmission Issues

I recent just had the vehicle Speed sensor replaced for $180. Ok for a couple days then driving down the rode only a couple blocks from the house and about 35 m.p.h. the engine does a severe downshift and I hear the "check engine light" come on. I had it checked at Auto Zone which said it could be low fluid, ...transmission failure. Checked the fluid it was way over max (I had just bought this Sedona 3.5 van). Anyway I removed 5 quarts of a very contaminated fluid; remove drain pain plug with 24 mm. I added 3 clean quarts back to a normal level. removed the neg cable of the battery to reset the code to an off position. Started the engine and check light returned within 2 minutes but no downshift. It's going back to the shop that put the VSS in it tomorrow. Note: there is a recall on these cables that may help us. I'll report back my findings. Note #2-I read if a VSS is replaced their must be a factory update to the computer or the above can happen! Stay tuned!

Transmission kicks hard once you stop after getting off the highway.

trany is slipping

Several problems: takes off fast when it shifts into second, lugs up hills, and won't coast down hills - seems to downshift itself.