ChevelleSSLS6

Here in the mitten state it's cold... and our subject is my 1990 Civic lx sedan automatic... aka Econobeater II...

Our story begins- In the summer and autumn, when it's warmer, the transmission shifted fine regardless of temps and showed no odd symptoms. Now it's wintertime, and in the cold it seems to not want to shift out of second gear until the engine is warmed. Today I was cruisin along 35mph @ ~4000rpm. I ended up going a bit slower to keep the revs closer to 3500 (figuring that mower engines run 3600rpm and last forever, that wouldn't hurt).

Once the coolant temp gauge stabilizes in the normal area ('water' at the base of the thermometer symbol) it might continue this for a little, but almost immediately shifts normally.


What I did so far...
I checked the transmission fluid with the engine and tranny warm (stop car, hold in all 'gears' for 10 seconds x2 and check fluid in neutral, engine running) and it appears to be ok.

I'm considering draining the tranny fluid and refilling, but I don't have an owners manual for it so I'll search for specs (what grade of trans fluid, capacity for a drain-and-fill) if the general consensus seems to say 'go for it'. I've just heard of a lot of guys messing their autoboxes up with new fluid as it dislodges otherwise harmless gunk that gets stuck in a valve or passage inside the transmission.

Since it operates normally when warmed up, I don't think it's a transmission mount issue as posted on a thread found during a search.

Mista Bone

likely seals inside the tranny, they swell enough to seal once warmed up.