Tonight car would not move, pulled ATF dipstick and it was black as night. Drained from the plug and flushed out from the input side of the cooler. Car would then move and shifted fine (drove it about 5 miles.) Wife said that morning the transmission felt like it was "slipping"

So now that I have treated the symptom, I'm trying to find out about the cause.
Any idea what causes black ATF? (Probably many different possibilites) but I would like to hear about anyone's experiences. Could the cooler line be clogged?

Thanks.

ATF will turn black if it is oxidized. Often, than is caused by high operating temperatures. It can also be caused by deteriorating clutch packs.

If I understand you correctly, you changed part of the fluid. If so, the fluid should already be very dark. I'd take a sample and send it overnight to a lab. They might be able to give you a better idea.

I'd probably do a complete flush, too, using a good non-synthetic. If that solves the problem for a while, send in another sample. If things are OK, then flush again with a synthetic ATF

Also, if the clutch packs are at fault. Is that something that is replaced (by a shop, not me) or is it essentially a rebuilt tranny?

In other words are the clutch packs a replacable item rather than the entire unit?

Just to clarify:

I did a complete flush 5K ago - ATF looked "used" but nothing out of the ordinary. When I saw the black fluid last night I did another complete flush (went home got tools and performed the work in the street). After the second flush I was able to drive the car. With the black AFT in the tranny, the car would not engage, after the flush it would and had no noticable problems.

I have 87K on the car now and I've performed flushes at 20K, 55K and 82K, plus the one last night at 87K. Each flush I used between 10 and 14 quarts.

I sent out the ATF to Blackstone Labs at 20K, came back as "ok but not outstanding" I'll have to dig up that report.

It has been hot here in the northeast lately. I'm still surprised that ATF went bad due just to the climate (if that's why it went bad.)

I'd like to use the synthetic stuff. I can't get it straight though: Volvo brand, Mobil 1, Amsoil, Royal Purple. Everyone has very strong beliefs on these as I am sure you know.

Thanks for your reply.

I should have added that I did the normal flush 5K ago! When I flushed that fluid it wasn't bad. I usually flush every 20 - 30k and it was due. Not bright red but not bad. This time it was black.

Can you remove the pan? If so you will find a lot of sludge. If the tranny just stopped and the fluid was black, the clutch packs might very well be fried.
Just flushing maybe the kiss of death for your tranny and an overhaul is in your future.

best of luck.

There is no such "pan" on a V70.

By flushing it I was able to get the car home and it drove just fine. I highly doubt that it was the kiss of death.

The "pan" is a called a valve-body pan and is located on the front side of the trans. It does contain a filter and most shops must partially remove the trans to perform service.The clutch packs are what the trans uses instead of direct, syncronized cut gears, only the output shaft has a planetary gear set to transfer the power thru the differental and out to the axle shafts.
The clutch packs will wear quicker when the fluid is low or restricted (bad or clogged cooler) or the pump pressure is too low to hold the pack, hence slipping will occur and more wear will take place. When too much wear happens, the trans goes into a downward spiral,wear-debris-slippage-more wear-debris etc.
You need to take the car to a good trans shop for a check.

Best regards,

Pedman

It is not normal for the tranny fluid to get that gunked up only 5k after a flush. Something is not right, and yes, it may very well be the end for yours.

Yes I agree, it's obvious that it is not normal. The question was what are some potential problems that could have caused this. Have there been instances of the cooler becoming partially clogged? Others?

Pedman mentioned "clutch packs". That is a definite possibility. Overheating of the tranny due to climate, clogged cooler, will kill the fluid also, but not that fast. Find a reputable Volvo indy mechanic or two and get a couple of expert opinions. If the problem is internal to the tranny, you are looking at a new or rebuilt unit, no questions.