Getting Dexron out of a BW35

Anders Hedelund

Anders Hedelund

Member
I did it: Topped up with ATF and then discovered it was Dexron. Flushing needed.

Most entries state that I have to repeatedly flush and refill, using up to 10-15 litres of correct ATF. Then I stumbled over this entry from the P5 forum. Appears reasonable to me: Let the pump do the work. Now this makes me wonder how is the ATF flow direction(s) to the the cooler and the torque converter?

Can anyone shed a light? "The ATF goes from the sump to xx and the to yy and etc.." Is there a drawing somewhere? The ones I found all show power flow.

And which of the lines to the cooler is the return one?

Ideally, then, one should be able to drain the box - let it drip off over night - fill in a few litres - unscrew a cooler line - start the engine - let the correct ATF push out the remaining DEXRON from the converter - stop again and fill up.

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Quote:

Flushing the gearbox
This is how I do it. Warm the gearbox...go for a drive. Choose a safe work area. Shut the car down and disconnect the fluid line that pumps ATF to the radiator trans cooler or air trans cooler. Direct this line into a large container. Start the car...leave it in PARK whilst idling. Watch the fluid being expelled (or have an assistant do this) As soon as the fluid flow falters switch off. Measure the fluid expelled and add the same quantity of fresh ATF.

This method may not be as thorough as a flushing machine but works for me. You can add a litre or 2 of fresh fluid before the old fluid is fully expelled.

Read more: BW35 transmission fluid | Rover P5 Club Forum
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How much dexron did you add?

What you say about draining off what's in the box and then refilling, followed by running the engine to expel what was left in the converter would work as the outlet to the cooler comes directly from the converter, I'm just not keen on doing it that way.

The method from the P5 forum isn't the same, because the pump picks up fluid from the sump, and that fluid is split between the box and the converter, and you have no way of knowing what fluid is going where.
 
And I'm not keen on dismantling the whole thing to empty the converter by hand. In such case I'd go for the full "heart-lung-transplant": During winter clean up and prepare the newer engine with BW65 that is waiting in the corner, and next spring drop in the lot. Then I shall need a cable linkage and brackets (btw. where can I get that - to Denmark?). But not for this year.

Ref P5/P6: I really thought it was the same setup..
 
Alas, I found attached illustration. So the cooler is in the return line from the converter - upper left hand corner direction 'lube' and 'oil pan'.

Then my engineering logic tells me with only fresh correct ATF in the pan and cut off of that line, the DEXRON will be pressed out of the converter to my waste bucket. Whatever is left anywhere else will be mixed up with the clean pan content, so the end result will of course be a mix up. But making a cut-off directly after the main deposit of DEXRON will speed ud the cleaning and minimize the need for repeated cleaning cycles. Or am I missing something.?
 

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Anders Hedelund said:
Then I shall need a cable linkage and brackets (btw. where can I get that - to Denmark?).
Click to expand...

When you decide what you need put a "Wanted" posting on here and I'll see what I've got. I've shipped to Denmark before and see know reason why I wouldn't be able to do so again. Unless free trade is prohibited after the UK leaves the EU. (If that ever happens....)
 
Anders Hedelund said:
Then my engineering logic tells me with only fresh correct ATF in the pan and cut off of that line, the DEXRON will be pressed out of the converter to my waste bucket. Whatever is left anywhere else will be mixed up with the clean pan content, so the end result will of course be a mix up. But making a cut-off directly after the main deposit of DEXRON will speed ud the cleaning and minimize the need for repeated cleaning cycles. Or am I missing something.?
Click to expand...

As I said before, the way you describe will work (certainly better than just running and collecting fluid from fitting to the cooler without doing a drain/refill first), but you'll never get all the Dexron out, and I don't like running it like that just in case the pump runs dry.
 
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