AWD Transmission: A consensus opinion on ATF change technique?

[Propofol]

Well, two drain and flushes used ala Clan's method and the fluid is not translucent like the new stuff but the viscosity is much less and just like the new stuff put in...I will change it again next year all being well.

I've given it a drive around until warmed up and it feels pretty good....it felt fine before.

I think I'll order 4x4.5 litres next and try the flush on the V70. That had a drain and flush at an indy at about 114K with some 3309 compliant stuff and felt like a new car afterwards...so it'll be interesting to see how it feels afterwards.

Thanks all.

[Propofol]

The only thing I have noticed is....I put 11 litres into the gearbox and only got out about 9 litres.

I have been out for a drive (not 30 minutes highway) and the level is at the top of the hot mark with the engine running and been through the gears twice.

I shall check again at the weekend after a 30 minute motorway drive - I suspect it's a bit overfilled and may well have been underfilled when I started.

The oil on the dipstick is now very red and clear even after a 15 minute drive around going through all the gears....I suspect I'll be syringing some out at the weekend...

[TurboZutek]

Originally Posted by ChrisE

As I have posted elsewhere I suspect that the necessity to change the oil could be reduced if there were a better gearbox oil cooler.

While that wouldn't do any harm, it wouldn't help as much as you might think. As the ATF ages and gets more and more particulate matter caught in it, so too it becomes more prone to overheating.

It's actually all the particles, condensation water and muck in it that change its thermal characteristics meaning the thicker and dirtier it gets, the hotter it will become in operation for a given work unit.

In that regard, ATF is somewhat similar to brake fluid.

To compound the problem, as components get a thick layer of dirt and varnish on them from the old fluid, the heat-sinking and dissipating power of the parts and the casing also reduces.

You'll notice the auto transmission runs cooler with just new fluid and no other modifications (well, on cars with a transmission temperature gauge anyway)!

Chris...

[ChrisE]

yes and overheating makes it age more quickly.

I don't know what the balance is but for those who tow & visit the Alps I am sure an oil coller makes more sense than for someone who lives in Holland & drives gently all the time.

I really regret that with all the electronics in my car I can't just display the gearbox temp on my dashboard display. The sensor, I am told exists to do that.

[TurboZutek]

Yes there's a sensor on the AT which measures the fluid temperature. The ECU uses that information to calculate line pressure equations to ensure smooth shifts.

Tapping into that sensor for a gauge is very simple (two wires), you just need a gauge that can handle a resistance output and is calibratable across the range. I've also seen a thermister installed in the sump plug for a rough and ready temperature gauge (though that output would be post-cooler).

If you want I can dig out the table scale of resistance to temp and post it, be a nice little project!

Chris...

[RoyMacDonald]

Originally Posted by Propofol

Well, two drain and flushes used ala Clan's method and the fluid is not translucent like the new stuff but the viscosity is much less and just like the new stuff put in...I will change it again next year all being well.

I've given it a drive around until warmed up and it feels pretty good....it felt fine before.

I think I'll order 4x4.5 litres next and try the flush on the V70. That had a drain and flush at an indy at about 114K with some 3309 compliant stuff and felt like a new car afterwards...so it'll be interesting to see how it feels afterwards.

Thanks all.

2002 V70's were fitted with autoboxes or geartronic boxes as an option. The autoboxes are straight drain and refill, the geartronic a pumped change.

It's the same box in both cases but with different programming triggered by the gear lever for overiding the auto change program in the case of the geartronic.

Change the ATF both boxes every 48k or 4 years.

[Propofol]

I'm not sure I understand why one is a drain and refill and the other a pumped change if the internals of the auto boxes are the same?

My V70 is a standard automatic, the xc90 the usual geartronic.

[RoyMacDonald]

Originally Posted by Propofol

I'm not sure I understand why one is a drain and refill and the other a pumped change if the internals of the auto boxes are the same?

My V70 is a standard automatic, the xc90 the usual geartronic.

I've wondered that myself. I assume there must be some slight modification with the geartronic or that as the geartronic mod is later and they decided that the pumped change gave a cleaner oil change. Never seen a reason given though. I don't think there can be a physical mod though as you can convert an auto box to geartronic by changing the selector and computer.

[Propofol]

Well I've now taken out about 1.75 litres, it sits in the cold region of the dipstick after 15 minutes of idling. I'll see where we are up to after a motorway spin....

The oil I syringed out looked pretty dark with a hint of redness but the viscosity was just like the new stuff that went in - it was also lacking the fine particulate sludge from the old fluid that sedimented out at the bottom.

Next time if I can get hold of some clear tubing of the right size I'll do the pumped drainage technique - where can you buy it from? I've looked everywhere...

[bobdabuilda]

Originally Posted by Propofol

Well I've now taken out about 1.75 litres, it sits in the cold region of the dipstick after 15 minutes of idling. I'll see where we are up to after a motorway spin....

The oil I syringed out looked pretty dark with a hint of redness but the viscosity was just like the new stuff that went in - it was also lacking the fine particulate sludge from the old fluid that sedimented out at the bottom.

Next time if I can get hold of some clear tubing of the right size I'll do the pumped drainage technique - where can you buy it from? I've looked everywhere...

B&Q sell the tubing