98 V70 Transmission Mystery

[zamoti]

I have a 1998 V70 GLT (auto) with about 135k miles and recently, it has developed a strange problem. When cruising at highway speeds and accelerating, all is well. When I lift off the gas and slow down enough for the trans to downshift, it does so rather clumsily. The effect is as if you're driving a 5-speed and put put the clutch down, then release it. Kind of that "humping" sensation (for lack of a better term). It will do this about three times when I lift from about 60 mph. Not sure, but it feels like it's happening between 3-2 shifts; it does not happen right after l lift, I have to be slowing toward 30 or something before it really starts. It also seems to be running rough when sitting at stoplights or cruising around 5 mph. Also I've noticed that since it's gotten a little colder out, the engine RPMs surge in the morning from about 1000 to 1500 for a few moments before it settles in. Previous history on this car is unknown, but from the day I bought it about a year and half ago, it's always had a bit of a bang in the 1-2 upshift when accelerating heavily-really kicks the whole car in the ass. I asked the my local Volvo guy about it and he said it was nothing, don't worry. So my concern is that my wagon is about to need a transmission; would changing the fluid (have no idea if/when it has ever been changed) be rearranging the deck chairs on the Titanic? I've no upshift arrow on the dash as I understand many other people get with tranny problems. I also have a perpetual check engine light due to the dumb air pump that I keep avoiding, but when I pulled the codes the other day I also got a P0133--front oxygen sensor. Would that produce the same transmission humping effects I'm experiencing? Sorry for the long post, and thanks for any information.

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[zamoti]

Anyone?
Bueller?

[tech]

I would try changing out the fluid and see what happens.

[zamoti]

Thanks, will give that a try and hopefully post back with good results.

[zamoti]

Front o2 sensor fixed odd downshifting, replacing transmission fluid did NOT fix 1-2 hard shift. However was only a drain & fill meaning that 'bout 1/3 of the fluid was replaced.

Any truth to the idea that a flush will knock something loose and ruin the transmission? I always hear that one and wonder what the heck gets knocked loose? If the system is that fragile, it seems like a few harsh potholes would knock something loose.

[tech]

The new fluid acts as a cleaner.
But if you disconnect the return hose and pump the old out and pour new in you should be fine.