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[Steve B]

was thinking ...if i leave the sumps off over night..can i get all the atf out of the gearbox

[Entwood]

Nope.

Dropping the sumps you can change about 50% of the ATF. Blow through the ATF cooler with compressed air may move another 5% ish ... the rest is sitting inside the box.

[Steve B]

so can i not do a 100% chainge on my box

[YZ250]

so can i not do a 100% chainge on my box

Seem to recall JamesV6CDX saying that you can get a fair amount more out by removing the solenoids. Not sure how much more though or whether it's worth the bother. 

[tgm147]

If you knew which hoses did what that went to the cooler, could you not run the engine with one hose going into a bucket and the other sucking fresh ATF back in?

[sassanach]

almost, undo the front pipe(if memory serves me correctly)run the engine at tickover to pump out the oil,when the flow stops,stop the engine,refill the sump and repeat untill the output flow runs with new fluid.reconnect everything and top up.much less hassle than dropping the sumps.NB tickover only!!!!

[sassanach]

i would also like to point out that the return cooler pipe does not "suck"fluid in so you have to refill the sump manually through the filler plug

[Cliffo B]

Thanks Sassanach for that brilliant info
I'd appreciate further clarification of which pipe to use to drain
My box is an AR35 if that makes a differance
Up to press since I did the sumps off/filter change job a couple of yrs back
When I also changed the atf spec to GM Dexron V1
I then discovered after that
That there was still about 50% of the old Dexron 111 left in to mix in
This really really pi**ed me well off
So in the end I finished up buying a Pella vacuum pump with the intention of extracting as much as possible mixed atf
And re-topping up with new GM Dexron V1 via the filler plug
This however is limited
As you'll know it allows only about a 4ltr changeover
I now add this job to my engine oil change intervals
With the object of ultimately finishing up with very little Dexron 111 content 
Have done it twice
And to bring things up to date
Have got 5 ltr of atf from Andy C
And about to do it again for the 3rd time

Now it's comeing!!!
No1 Do I carry on as before?
No2 Now carry out a full drain and fluid change
As Sassanach's suggested method
The purist in me say's No2
The economist say's No1 (ATF is not cheap)
The Autobox is presently performing 1st class with no problems
So of course I will much appreciate the experts opinions/comments
Especially from Sassanach
Thanks

[Steve B]

i get the idea that there are 2 pipes going to the oil cooler.. if that is so. what if i undo both and point them at a bucket on tick over until flow stops  .then reconnect and refill.....am i getting it wrong here  ..

[markfree]

i get the idea that there are 2 pipes going to the oil cooler.. if that is so. what if i undo both and point them at a bucket on tick over until flow stops  .then reconnect and refill.....am i getting it wrong here  ..

1 pipe is feed (the 1 going into top of cooler) the other is return ( bottom 1) - you just need to undo feed pipe, bleed the gbox, reconnect and re-fill.................seemples 

[JamesV6CDX]

Once emptied, refill with fresh ATF, RECONNECT THE PIPES, then let tick over as normal for a while, before again disconnecting, re-filling, and so on.

If you drain it, then put new ATF in and immeditely let it keep draining, it will just pump out your nice fresh ATF, rather than circulating the old stuff through... 

[Kevin Wood]

Once emptied, refill with fresh ATF, RECONNECT THE PIPES, then let tick over as normal for a while, before again disconnecting, re-filling, and so on.

If you drain it, then put new ATF in and immeditely let it keep draining, it will just pump out your nice fresh ATF, rather than circulating the old stuff through... 

I read it that you add clean fluid, which the pump then picks up, displacing more old fluid in the gearbox, so you need the pipe disconnected until it runs fresh to get rid of this old fluid, rather than pumping it back into the box.

Once the pipe is running clean fluid, you then reconnect it and top up.

[Kevin Wood]

Hmm. Anyone dissected a gearbox enough to find out where the fluid cooler circuit is fed from and returns to?

[Cliffo B]

So if I i'm reading you correct it's not possible to drain all the systems atf in one go
possibly could cause damage through lack of fluid and engine running
Think I'll play safe and carry on as before:-

Miggy level on ramps
Drain main sump with Pella via level plug (about 4ltr)
Refill till fluid exits from level plug
Reconnect plug
Start engine and further top up till fluid exits
Reconnect plug
Job done 

 

[Kevin Wood]

There's quite a lot of fluid in the torque converter, in fact I'd say that's probably where the majority of the remaining fluid is once the sumps are empty.

Only way you'll get that out is to take it out of the car and even then it can be a challenge to get it all out!

I've heard it said that you can cause a box to draw fluid in via the fluid cooler return when flushing by blocking the breather so the departing fluid creates a partial vacuum in the box, drawing in fresh. Haven't ever tried it, though.

I doubt the pump would be damaged unless it was run long enough to dry out following the sump emptying. Couple of seconds should be OK, but hence sassanach's comment, I suspect, - idle speed only!