Changing automatic gearbox oil

[Mothman]

Is this a difficult job? Can anyone tell me where the drain plug is as ive decided to change Gloria's fluids.
Malcolm has just told me that you cant get it all out and that if you top up with the reccommended 2.5L of Dextron 2 you will probably over fill it.

Andy

[Way2go]

Not really. Remove the drain plug, drain & then refill via the dipstick tube. You can't drain all the oil because you can't drain the torque converter. Therefore when refilling check the level frequently until close. When nearly there, run the engine to draw fluid into the torque converter and warm up to perform the final fill to the level mark.

PS: To make it easy, the 1L Fluid bottles come equipped with a tube to insert into the dipstick hole - no funnels necessary!

[Mothman]

Thanks for that bud.

Andy

[Way2go]

You're welcome!

Incidentally, if you overfill you will find that the gears "clonk" when changing - so you will know if you've made that mistake. If this happens then use a syringe with a tube on the end to draw sufficient fluid back out of the box through the dipstick hole and you will find your changes will again become smooth. Another reason its not good to run at too high a level is that it can degrade the oil-seals so best to not let it linger before sorting.

[Thread Bear]

So there is no real way to purge the entire 6.5 lt of ATF in one sitting. It sounds like a pain in the arse, and a lot of ATF chucked, to clean out the 20 year old fluid.

[mds141]

I've done the auto on the XM a couple of times now. Usually get three litres out at a time. The TC does hold onto at least half of the boxes capacity. Don't forget to clean out the filters in the bottom of the auto box sump and clean the swarf off the magnet.

[mds141]

Copied from the XM forum, Deans famous auto box fluid change guide...http://www.club-xm.co.uk/forum/viewtopic.php?f=13&t=71" onclick="window.open(this.href);return false;

[Thread Bear]

Thanks, Indeed must include the filter set up. Give some idea if all is well. No reason to think not, but the fluid looks horrible. Not part of MOT either but non the less.

I wonder if it works as two stroke, probably too thin. Good old Sachs burns pretty much anything. Hate throwing stuff away you know.

[MULLEY]

Is there no way it could be drawn out via the syringe method in order to get the really mucky atf out? Does seem like bit of a design flaw?

[jamescarruthers]

Does the BX have the ZF4HP14 box in... if so it is true that you can't ever get the lot out as the torque converter keeps some inside.

Other cars (I suspect the XM would be like this) have an external oil cooler which you can use to pump the old oil out and the new in by disconnecting the cooler and feeding new stuff in as the old is sent out.

Without an external cooler to have the fluid sent out to you you are stuck with the method of leaving some in the torque converter.

There may be a little external cooler with a banjo bolt on which is more like the oil filter on your engine with engine coolant running around it. The easier to flush type could be imagined like your car radiator but with oil instead of coolant and coolant instead of air.

You could change the BX type many times to get it diluted and then change it fairly often after that to avoid being left with 20 year old oil which is waaaay past its change date.

I hope this helps as opposed to confusing matters.

I only know about this type as I had a 480 once with a autobox similar to the BX's. It finally needed to be rebuilt as it's changes must have been neglected. Cost me £1000, which is crazy money to spend on a BX or 480!

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[jamescarruthers]

Just checked on Google, it is the same box as the 480 I had. So to summaries my above waffle, the BX box can be diluted with a lot of new stuff but never changed completely unless you strip it down and remove the torque converter, which you can't.

In 480's we are very surprised with the same auto boxes making it past 100k. I think the 480 Turbo's power (not huge, but more than the BX's) is at the peak of what the box can do and also the oil changes get neglected terribly in auto boxes. Mine died at 55k but as I loved it I somehow managed to justify the expence. I wish I could buy that one back!

I've read that XM guide, it's fine but the BX is much simpler as there are no filters or anything. Basically, drain from the plug and refill through the dipstick.

And take great heed of the level as overfilling will kill it. The level is checked with the box warm (like the XM guide says, the dipstick has a warm and cold side) and after having selected every gear. I wouldn't drive it one metre until I'd checked it a few times and was absolutely certain.

Basically the box is weak so look after it and once you've got it's oil clean change it regularly.

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[Thread Bear]

Sounds a pretty crap bit of kit, all in all. You can only change a max of about 40% of the fluid at a time, effectively. Is this a gearbox that is weak, or a production engineering own goal, as it is impossible to keep the thing in perfect condition? This one has covered about 40k so has a chance, if the fluid can come out. I can sense my interest waining rapidly. I have little patience to idiotic build quality, unless there is a reason for it, or it does not matter and is eccentricity. The BX is becoming painfully obviously infested with sillies spoiling what should be a good car. Most a product of production choice, and can be modified out, but others are real minus points. I am waiting to see the logic of the 'non adjustable' clutch. I bet there is a load of meat on that plate. Still its one part that works well in all this damp!

[mds141]

The ZF 4 HP 18 is a fundamentally sound design. I know of XM's with over 200,000 miles on them and running fine. Plus thousand of Yank tanks are fitted with the same 'box.

The later adaptive 'boxes don't even have a drain facility and are supposedly sealed for life, with subsequently disastrous results.

[rutter123]

i was always under the impression that to completely change the auto g/box oil you will need to drain/refill, drain/refill again a few miles later then drain/refill once more as the torque converter holds as much oil as the g/box itself, so effectively you are only changing half the oil mixing new with old as it were. Quite an expensive operation but unfortunately no easy way around it, unless the oil is changed on a regular basis to "keep it clean".

Sadly lack of proper maintenance saw the death of my tgd auto box hence it now being converted to manual.

[mds141]

I've developed the routine of changing the auto box fluid with every engine oil/filter change, ie every six months or 6000 miles. Dexron 2 is relatively cheap and certainly much cheaper than a transmission rebuild.