Auto box Oil change

[arcturus]

93. 940 GLE auto.
Hi, what's the best way to do a complete oil change on the auto trany. I feel that after 25 years of hard work it would be beneficial although the car has done less than 90,000 miles.
The book says Dextron 11E or 11E. If unavailable what would be the equivalent?

[360beast]

Queue the ATFU carlube salesman

Drain the oil out of the gearbox, drop the sump, renew the filter. Apparently NLA from Volvo but it was also used in a Toyota according to Barkster so you can get one from the US and then replace the sump gasket. Fill it up until it says minimum, start the car and run it at a standstill through all the gears for a few seconds in each to suck the oil level down. Repeat until the oil level stops getting sucked down, make sure the oil level is at minimum because the next step is to go for a drive, as the oil gets hot it expands and the level will go up, top up if needed.

[Forrest]

I changed mine a few years ago using the Gibbons method. Undo the top cooler line at the radiator, attach a hose and put the other end of the hose into a clear bottle. Run the engine to pump about 2-3 pints of fluid at a time into the bottle. Top up with the same amount of fresh fluid and repeat until the fluid runs clean. This takes more fluid than the capacity of the system but is very effective if you want to change all the fluid.

[Laird Scooby]

On an old box, even a low mileage one, it's not advisable to change the fluid using the flushing/gibbons or whatever other names this method of renewing all the fluid in one go is.

Much better to do several "part-changes", sometimes referred to as "sump-dumps". Like Luke said, Carlube ATF-U for the fluid and Toyota A341E box is the same apart from a slight difference in output shaft, seal and bush as the AW71 box.

There are many reasons for doing part-changes in preference to flushing changes, main one is that the fluid and more importantly, the seals in the box are old. The fluid will have lost its "seal-swell", a nickname for the seal conditioner in the ATF so the seals inside the box will have dried out and become brittle. If you then fill it completely with new, thicker fluid, the seal-sell in it won't have time to revive the seals before full working pressure is achieved. This can lead to damaged seals and all that entails. Doing it gradually means the seals have a chance to be revived by several part changes with the fluid getting thicker and cleaner each time. This also cleans the filters out for you unless they're absolutely blocked, in which case, you'd have no drive at all.

I've successfully used a 12V oil extractor pump down the ATF dipstick tube, takes about half hour to empty it but with the car facing slightly downhill, also helps remove any sediment in the box that will settle to the bottom/front (facing downhill) rather than being circulated round the system by the engine being run with the other methods.

[arcturus]

So, do a part drain, refill, run for a few km's and repeat the process two or three times. How mamy k's between each flush would be optimal? I don't do much mileage.Also should I do this hot or cold?

[Laird Scooby]

Originally Posted by arcturus

So, do a part drain, refill, run for a few km's and repeat the process two or three times. How mamy k's between each flush would be optimal? I don't do much mileage.Also should I do this hot or cold?

Drain the ATF hot, it comes out easier and brings more dirt with it.

Undo the sump drain plug if you have one, use an electric oil transfer pump down the dipstick tube if not to get as much ATF out in one go as possible.

Refit the drain plug, refill with fresh ATF to the correct level (somewhere between 2.5 - 3.5L usually) then use the car.

As for the repeat interval, if the ATF that came out on the first drain was dirty go about 5-800km, if the fluid was cleaner, go 8-1600km and repeat. Usually it will need one more repeat after this so a total of 3 part-changes. Repeat one part change yearly after to keep the ATF clean and in good condition.

You can see how dirty the ATF is using whitepaper towels by dribbling some onto it. The ATF will spread through the towel and the dirt will show up against this.