Does anyone know if the Kia uses 80/140 trans oil/stick shift. I put in 80/90 and it gets hard to shift when the weather is hot and Ive been running for some time. I noticed the shifting is nice and smooth when it is cold, so the oil must have something to do with it. I thought it was my clutch, had for 6 years, but then it would be hard to shift all the time. It does not screech or anything like that, it's just heavy shifting when temperatures are hot. How about the diffs and transfer case oil? I used 80/90 all around.

1985 Toyota 4x4 4Runner. 1989 Suzuki Sidekick 4x4.