Cold Weather Minor Transmission Flair

Post by **BlackBart** » 29 Dec 2021, 12:17

I've read much here at MVS about "transmission flair" between shifts. I experienced an odd and very brief thing on my recent trip.

Very cold weather, below zero fahrenheit. Long freeway drive. Pull off the highway to gas up and come to the first stop, like the top of the off-ramp. On the slow acceleration right after that stop, I got a brief shift flair between gears. Sort of caught me off-guard, I wasn't sure what I was hearing, since my car ('04 XC70) has never done that. It only happened on that one shift, at two different gas stops.

Car is in good shape, and I've drained and filled new Toyota ATF twice, so that's around 7 qts. Color is good.

Just curious if this is a case of a transmission humming along in top gear for a long period in bitter cold, then the cold valves are asked to perform suddenly after a stop.

Post by **vtl** » 01 Jan 2022, 23:04

One flare in unusual weather wouldn't concern me too much. What gear did flare, btw? 2-3?

Post by **chrism** » 02 Jan 2022, 07:30

My 2003 V70 used to do that on occasion on the coldest of mornings. It was always when I accelerated out of my neighborhood, turning left and heading slightly up hill. I was able to stop the flair by slightly overfilling the trans fluid by somewhere between 1 cup and 1 pint.

Post by **volvolugnut** » 02 Jan 2022, 08:45

chrism wrote: ↑02 Jan 2022, 07:30 My 2003 V70 used to do that on occasion on the coldest of mornings. It was always when I accelerated out of my neighborhood, turning left and heading slightly up hill. I was able to stop the flair by slightly overfilling the trans fluid by somewhere between 1 cup and 1 pint.

The problem and solution are consistent with the facts that the ATF will shrink in volume in cold weather and slosh to the side of the transmission in a turn. I have experienced the same in a Mercedes transmission and applied the same solution.
In the case of BB transmission, the cold and wind may have chilled the fluid enough to delay the shift. It would be interesting to monitor the transmission oil temperature in these weather and drive conditions.
volvolugnut

Post by **BlackBart** » 02 Jan 2022, 12:18

vtl - I’m thinking it was the first shift pulling away from the stop (unless the 1-2 shift is very soon and almost imperceptible, then it was 2-3)

Post by **- Pete -** » 05 Jan 2022, 00:23

Just a suggestion, you may want to see if there are any codes lurking.

Recently, on my 311k mile XC I’ve noticed a “bump” in the driveline ~ 1 second after shifting into 2nd gear, almost as if the torque converter lockup has been delayed & upon command, abruptly engages.

I would say that most “in tune” drivers would dismiss/fail to recognize the sensation. I just haven’t been able to get it out of of my crosshairs since I noticed it. At 311k miles (on original equipment) a trans rebuild/replacement would certainly not be a surprise.

Anyhow, today I retrieved codes on it & Lo & behold, I kept seeing a P0573, circuit High. This relates to the brake pedal position sensor (failure). I replaced it today & topped off the trans with ~ 1 cup of ATF (it wasn’t low) and the sensation hasn’t repeated itself. Mind you, this thing happened EVERY single time approx 1 second after shifting into 2nd gear prior to this.

Post by **abscate** » 05 Jan 2022, 01:48

Sometimes being in tune is your enemy…my ME7 cars with AT both unlock the torque converter for a second when you come off float, then lock. Still don’t know if this is normal or by design. This is one easier to see because you see it on the tach

Post by **vtl** » 05 Jan 2022, 07:31

abscate wrote: ↑05 Jan 2022, 01:48 Sometimes being in tune is your enemy…my ME7 cars with AT both unlock the torque converter for a second when you come off float, then lock. Still don’t know if this is normal or by design. This is one easier to see because you see it on the tach

It probably disengages the 2nd coast clutch (B1). May even feel like a slight jerk on a worn transmission and/or old fluid with little additives left, so clutches disengage harshly. Volvo ATF or 1-2 oz of Lubegard HFM may help.

Post by **- Pete -** » 05 Jan 2022, 09:30

abscate wrote: ↑05 Jan 2022, 01:48 Sometimes being in tune is your enemy…my ME7 cars with AT both unlock the torque converter for a second when you come off float, then lock. Still don’t know if this is normal or by design. This is one easier to see because you see it on the tach

So true!

What do you mean by “when you come off float”?

The “bump” I previously felt was not something I could detect on the tach - odd, but I could still feel it. It wasn’t a shift flare either, occurring well after the completed 2nd gear shift. I didn’t time it, but it was ~ 1-3 seconds after 2nd gear upshift completion. Of note, I pay particularly close attention to ATF; drain & fills (~4qts) every 12k miles (every 3rd 4K mile oil change).

After palpating the “bump” & subsequently seeing the P0573 I immediately flashed back to OBS Ford nerdery where discussions involving torque converter lockup parallel my thoughts. In OBS Fords (E4OD trans), while maintaining unvarying speed, if you gently tap the brake pedal (just enough to illuminate the brake lights) the torque converted unlocks & RPM’s rise just enough to be noticeable on the tach (1-200 r’s).

Now I have no idea if the AW trans has some torque converter lockup feature linked to the brake pedal position sensor, but after replacing mine (junkyard sensor) the bump is gone, and so is the P0573. There’s a slim chance the additional cup of fresh ATF I added helped? Dunno.

Another interesting thing I’d like to make note of (and I apologize for my lack of brevity) is that all 3 of the sensors I collected from the junkyard we’re identical (2002 V70XC, 2004 XC70, and a 2006 XC70).

When I called the dealership they quoted me $185 for a new sensor. On FCP, there are 2 different part numbers listed for the range of years; some years call for switch “A”, some call for switch “B”. Before I spent money on this theory I figured I try a junkyard sensor.

This is the switch I found in all 3 cars. This style switch, as fitment shows, fits 2001 V/XC70’s (amongst others). https://www.fcpeuro.com/products/volvo- ... te-9441116

This is the other switch, which fitment shows fits 2003-2007 XC70’s & 2002-2007 V70’s. https://www.fcpeuro.com/products/volvo- ... 06#fitment

I think either switch would probably work, not sure why they changed the position of the electrical port. Anyhow, I’ll refrain from feeling elated just yet & will of course continue to keep a close watch on 2nd gear post-shift behavior.