Transmission fluid change via vacuum pump

[Andymharrison]

Originally Posted by Simmy

i prefer to go under and drain using the drain plug you can also check other components whilst underneath. exhaust. suspension . bushes cv boots. ect .

All very true, if you are able, I did quite a bit of work on my xc90 last spring/summer but the return of recurring back trouble and a rotator cuff hurting mean that by the time I'd got under the car I'd be done for the day!

It needs a service though and I would prefer to do it myself and know it was done with the right parts, a vacuum extractor will enable me to.

Plus I'll save a decent amount of money that I can put towards paying for the jobs I doubt I can physically do just now, such as those rear bearings rumbling to themselves...

[Kev0607]

I have a vacuum pump, I use it for oil changes and it works very well without the faff of having to jack the car up and remove the undertray. By the time I'd do that, the oil is nearly sucked out!

I don't think my vacuum pump has a thin enough tube to fit into the transmission fill plug to suck it out, but in saying that, I haven't tried.

I always hear about people "settling the level", i.e. getting underneath the car when the engine is running and gearbox fluid is 50-60 degrees and then undoing the small drain plug (not the big one) to drip any excess fluid out. The car needs to be level to do this, but that's not easy when you're working off jacks.

Am I right in thinking if you suck the fluid out and add exactly what you suck out that you don't need to do this reset? You can reset the transmission fluid change counter so the car knows its got new fluid, but is the level setting necessary?

[Tannaton]

Originally Posted by Kev0607

Am I right in thinking if you suck the fluid out and add exactly what you suck out that you don't need to do this reset? You can reset the transmission fluid change counter so the car knows its got new fluid, but is the level setting necessary?

In principle you are right to think that but it does assume the fluid level was correct to start with.... which you can't know so it's best to set the level. I don't use VIDA to see the temperature - I just drive 5 miles or so.

The fluid change counter is just that and changes nothing, but you should reset the adaption memory to get the most out of the fluid change (though not essential).

[al dm]

Originally Posted by Tannaton

It's pointless.... whether you drain it or suck it out, when the engine is not running more than half the fluid is trapped in the torque converter, differential housing or other parts of the gearbox. Whether you drop it or suck it up, you will always get the content of the main casing.

Well, it's not pointless if you do it a few times. You'll never get all the fluid out and changed for fresh, but what you will do is get fresher fluid on average.

When I got the two XC70s that our family has, I would drain or suck the approx 3L out and replace with the same amount of fresh fluid, then repeat every week four or five times.

Over time, you can clearly see the colour of the fluid change from the old muddy black/brown to a much clearer reddish colour.

I'd call it a fluid refresh rather than a fluid change.

[Kev0607]

Originally Posted by Tannaton

In principle you are right to think that but it does assume the fluid level was correct to start with.... which you can't know so it's best to set the level. I don't use VIDA to see the temperature - I just drive 5 miles or so.

The fluid change counter is just that and changes nothing, but you should reset the adaption memory to get the most out of the fluid change (though not essential).

Well, with respect, you can know. If you suck 2.5 litres out with a fluid extractor for example, that means the transmission is 0.5 litres low. You can't drain more than 3 litres out of the TF80-SC transmission, even via the plug underneath. If you do, then it was overfilled to start with. If there's significantly less than 3 litres, its low because maybe enough fluid wasn't added the last time or there could be a leak.

If you sucked 3L out and replace with 3L, then you can't be wrong. 3 litres is the right amount for this particular transmission.

Originally Posted by al dm

Well, it's not pointless if you do it a few times. You'll never get all the fluid out and changed for fresh, but what you will do is get fresher fluid on average.

When I got the two XC70s that our family has, I would drain or suck the approx 3L out and replace with the same amount of fresh fluid, then repeat every week four or five times.

Over time, you can clearly see the colour of the fluid change from the old muddy black/brown to a much clearer reddish colour.

I'd call it a fluid refresh rather than a fluid change.

Yep, its a fluid refresh really, but a fluid refresh is better than nothing at all!

May I ask which fluid extractor you have? So you don't mess around setting the level in the transmission either, as you don't drain from underneath? This is music to my ears.

[al dm]

Originally Posted by Kev0607

May I ask which fluid extractor you have? So you don't mess around setting the level in the transmission either, as you don't drain from underneath? This is music to my ears.

It's just a cheap 6L Chinese one from eBay. Not great, but gets the job done. I think it cost me about £30.

Like this one: https://www.ebay.co.uk/itm/394450497...Bk9SR6SGy_SmYw

It came with five different thicknesses of extraction pipe.

I do set the level in the transmission - but only after the final fluid drain/refill session. I figure if I measure what came out and refill with the exact same amount, then it's "good enough" until the final cycle.

I have done 4 or 5 drain/fill cycles, then called it a day and set the level underneath the car. Which is a pain because it needs to be level, so I drive it onto 4 blocks of wood just to get a few more inches of clearance underneath.

[Kev0607]

Originally Posted by al dm

It's just a cheap 6L Chinese one from eBay. Not great, but gets the job done. I think it cost me about £30.

Like this one: https://www.ebay.co.uk/itm/394450497...Bk9SR6SGy_SmYw

It came with five different thicknesses of extraction pipe.

I do set the level in the transmission - but only after the final fluid drain/refill session. I figure if I measure what came out and refill with the exact same amount, then it's "good enough" until the final cycle.

I have done 4 or 5 drain/fill cycles, then called it a day and set the level underneath the car. Which is a pain because it needs to be level, so I drive it onto 4 blocks of wood just to get a few more inches of clearance underneath.

So 4 blocks of wood... I assume you mean one under each wheel? What size blocks of wood are we talking?

Any garage I've used to do the transmission service simply drained it and filled it again (once). That's not really going to solve much I wouldn't think? By the sounds of things, it needs to be done multiple times to get close to having a cherry red colour like it should be.

[Tannaton]

Originally Posted by Kev0607

Well, with respect, you can know. If you suck 2.5 litres out with a fluid extractor for example, that means the transmission is 0.5 litres low. You can't drain more than 3 litres out of the TF80-SC transmission, even via the plug underneath. If you do, then it was overfilled to start with. If there's significantly less than 3 litres, its low because maybe enough fluid wasn't added the last time or there could be a leak.

If you sucked 3L out and replace with 3L, then you can't be wrong. 3 litres is the right amount for this particular transmission.

I see your logic but it's just simpler and much more precise to undo the little screw and set the level....

[al dm]

Originally Posted by Kev0607

So 4 blocks of wood... I assume you mean one under each wheel? What size blocks of wood are we talking?

Any garage I've used to do the transmission service simply drained it and filled it again (once). That's not really going to solve much I wouldn't think? By the sounds of things, it needs to be done multiple times to get close to having a cherry red colour like it should be.

Just bits of 2x4 each a foot or so long. It doesn't raise the car much, but just enough that I can slide underneath it to access the drain plug.

The other (and better) option would be four low profile ramps, but I don't have any....

[Kev0607]

Originally Posted by Tannaton

I see your logic but it's just simpler and much more precise to undo the little screw and set the level....

But you don't need to set the level if you drain out 3L and put the same amount back in. There won't be anything to drain? Maybe a few drips at most, we're not talking litres of fluid I wouldn't think.