More Odyssey transmission questions

Our 2001, regularly maintained, Odyssey has only 208,000 miles on it, and the transmission has begun to misbehave. Similarly to a clutch’s slipping with a manual transmission, sometimes the automatic transmission will “slip,” that is the engine will rev without the car’s moving. This has been most noticeable, and until recently only noticeable, when the car is first driven on a given day - usually not apparent once the car has “warmed up.” My wife and I have independently observed that the problem is more apparent in colder, rainy weather. The problem seems to be getting worse - we’ve noticed occasional slipping now, for example, when accelerating to pass on a steep uphill.
Question 1: How might the association between the slipping and cold weather/engine temperature be explained?
Question 2: The Odyssey is about due for a new timing belt and water pump. That would seem not worth doing unless the transmission were fixable, in which case, it would seem best to take care of everything at once. Should we do it, or is it time to retire this car? (We live out in the boonies and have to contend with dusty roads in the summer and drifting snow in the winter; we don’t need a fancy car, but do need a reliable one - especially in the winter.)
Thanks.

It slips less when warm due the expansion of internal parts and the fluid thinning out. Has the fluid and filter on the tranny been serviced recently? If not you could try that and see if it helps.

Any slippage is a sign of impending doom. Don’t wait for the snow drifts. Either replace the transmission now or the vehicle. There is no advantage to doing both repairs at the same time but you could save money by not doing the belt ($500+) and the trans ($3000+) at all.

What happens when the transmission oil and the transmission are not fully warm is that the piston seals of the clutch packs don’t seal well. Clamping pressure is lost and the clutches do not hold. Another spot oil can be lost is at the shaft seal rings where the oil exits the case to enter the shafts on the way to the clutch pistons. These are seals are affected by mileage and age.

The transmission will probably have to be rebuilt. With this many miles on the transmission there is a possibility that hard parts, i.e. bushing, ball bearings, needle, and roller bearings might need replacement in addition to the standard rebuild kit of frictions and seals. You should decide how many more miles you plan to put on this van. With that in mind you can decide to rebuild this transmission, install a used low mileage one, get a factory rebuilt unit, or buy new.

Hopefully someone with knowledge of the reliability of the Honda Odyssey will rely to help you here.

Thanks all for your comments. Bottom line consensus was if car were to be depended upon, transmission had to be replaced. We opted for retiring it.

Count yourself lucky to have gotten over 200k miles out of that transmission. Not Honda’s finest. Good idea to put it out to pasture.