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tmcmilli
07-13-2014, 02:49 PM
After running the A/C for most of the last several weeks now, I've observed when driving in city traffic (when there are more shifts due to stop and go driving) and only when running the A/C, sometimes the car seems to shift a bit hard. But this ONLY happens when shifting up from say 2-3 or 3-4, maybe even from 4-5 at EXACTLY the moment when the A/C clutch re-engages the compressor during its normal cycle of disengaging then re-engaging. They aren't nasty shifts but not as smooth as at all other times. And I'm concerned about anything that could cause extra wear and tear on the transmission over time.

Has anyone else experienced this phenomnon? Could this indicate that the A/C compressor clutch is not re-engaging the compressor as cleanly or gently as it should, and is dragging down the motor more than normal at exactly the point where the transmission shifts, causing a harder shift? Or might this be a transmission issue? Or does this sound like normal behavior and is nothing to be concerned about? I never notice any hard shifts except under this particular scenario when the A/C is running, and even then it doesn't occur frequently. It seems that the timing has to be just right between the compressor engaging and the shift point occurring for a harder shift to occur.

Luna1973
07-13-2014, 03:13 PM
Although not connected to my air con (as I don't normally require it in Scotland), I had as you described 'nasty/rough' gear changes.

Took it to my local Indy Volvo garage who intimated that a change of the auto transmission oil could help.
Oil was expensive, approx 16 dollars per litre, and it needed nine. Labour was only 30 min. All in all about 200 dollars.

However it has made a massive difference to the gear changes, no more clunks or rough changes.

Hope this helps.