I've got an '84 Pontiac Firebird (130K) w/ a 700R4 overdrive automatic. I noticed this once or twice last year and again the other day when it dipped to about 30F locally. The transmission wouldn't hold or maintain
4th (OD). Basically I could be driving along on flat expressway with only the occasional overpass and the thing would almost constantly jump back and forth between 3rd and 4th for the entire drive.It just seems that the problem of jumping down to 3rd and not holding occurs specifically when it's cold OUTSIDE. Now on any cold morning for a few minutes it can be a little balky about shifting but this quickly goes away within just a few minutes. But yesterday even after 40 minutes of driving to work it doesn't seem to get any better as far as OD specifically. I would think that within a 40 minute drive of mostly
65ish cruising that the transmission would be completely warmed up and immune to outside temps.Maint background: Every 2 or 3 years I drop the AT pan and replace about 5 qts and change filter. I don't use any special synthetics - just standard Dexron that meets the owner's manual spec. Level is between full and add last I checked. Transmission works just about flawlessly 362 or so days out of the years. It's just those 2-3 days a year we get down well below freezing that it 'hunts' and can't hold 4th (OD).
I'm wondering if anyone has seen this or has an explaination of why it would not 'hold' 4th (OD) at cruise when it's below freezing outside. Would temperature exacerbate a low fluid condition?