Transmission shifting

#1

I have a '99 Astro(hence pilot) that shifts a little slippery from 2nd to 3rd but only when it’s cold. Will changing the fluid help? It’s been about 60K miles since it was done.

#2

Changing the fluid can’t possibly hurt, and may help. I suggest you have the transmission fluid changed. The owner’s manual should tell you how often to change the transmission fluid.

#3

Thats your 2-3 clutches starting to go. This transmission is known for its weak 2-3 stackup, this is why I upgrade them every time one crosses my bench. As far as the fluid change goes, service an automatic transmission by dropping the pan, changing the filter then refilling every 25-30k miles regardless of what the owners manual says. Owners manuals are good for letting you know what every little doo-hickey on your dash does, or how to get at your spare tire and jack but as far as service intervals go, ask a pro. Want to know how often to change your oil? Ask someone who rebuilds engines for a living. Want to know how to properly service and how often to service an automatic transmission? Ask a transmission rebuilder.

transman

#4

Actually the service intervals are mostly good. However I agree when you look at transmission service recommendations they are totally lacking. The service tansman recommends and the interval he recommends is right on.

And don’t fall for that old tale that transmission fail right after a fluid change. It is only true because so many people never get their fluid changed until the experience problems like you are now. An earlier change might have done some good, but now changing the fluid is not going to undo the damage that was done because it was not changed earlier.

#5

Some of these responses are right on the money in many respects, but my question was, “Why, after it heats up, the transmission shifts properly?” After I drive for about 4 or 5 minutes, I feel no slippage between 2nd and 3rd. Thanks for the input.

#6

Heat expands the clutches

#7

What happens is the rubber clutch piston seals harden over age. When they harden, they do not seal properly and hold hydraulic pressure which is the clamping force on the clutch. When the seal leaks the clamping force on the clutch is lower causing the clutch to slip. When cold, the old hardened seals tend to leak more. As the transmission heats up, the seals soften and will seal better.

transman

#8

Ok, so this is what I wanted to know. If heat causes the seals to soften and therefore work better, why should I spend lots of money on replacing parts that work OK when warmed up? ( aside from changing the fluid)

#9

When the clutches are slipping, they will wear out quicker. Then they will slip when warm.