Automatic gearbox woes

Many modern autos don't have drain plugs - the fluid is designed for their lifetime. And if yours is one of these, you'll probably find the correct stuff isn't just a couple of quid a gallon.

Is the fluid obviously dirty? If it is, this denotes break up of a clutch lining material etc, and changing it won't help. If it's clean, changing it wouldn't help either. ;-)

If the over filling was such that the fluid was being aerated by the gears as it expands when hot, this would reduce the line pressure resulting most likely in things slipping.

If there's no drain plug, you could buy some plastic tubing from B&Q etc that would fit down the filler tube and pump/syphon out the excess, and keep your fingers crossed.

The big snag with changing the fluid is that a considerable quantity will remain in the torque convertor, which can't be drained. So any contaminate in the fluid would simply be diluted with a change. Because of this, it's common practice to replace the torque convertor at overhaul time - regardless if it is faulty or not.

The message from Dave Plowman contains these words:

Are you absolutely sure it's overfull? There are rather complex routines for checking the level which involve arcane procdures like warming it up, moving through all the gears slowly then turning round and spitting before wiping the dipstick with a piece of mistletoe.

Just dipping it cold with the engine off will usually show overfull.

Just a question, here - if it is dirty / blackened or contaiminated, is there a possibility that fresh fluid might help, if the damage to create the contamination isn't catastrophic? Or is that scenario unlikely?

For some autos, though, some people tap into some of the cooler lines, and actually use the torque converter to pump out fluid, whilst fresh is added. You have to be reasonably careful, though, and may need to stop and start the engine to catch up the rate of it being pumped out - might be difficult as a job for one person. Using a procedure like that, it would be possible to totally replace the fluid, wouldn't it?

Assuming that tapping into these pipes is possible, and that there is actually a filler tube, or some other means of tapping in to add new fluid. Depending on where you break into these pipes / hoses, though, you may not get at the fluid in the cooler.

I'm not.;-) I'd think it very unlikely to be the problem. But the OP has high hopes.

IMHO, unlikely. Once a lining starts to break up, it will continue. And if debris has lodged in the valve body, draining and refilling is unlikely to remove it, as it was deposited there under pressure.

Yes, you could do this, although you'd have to be careful not to introduce more muck when you disconnect the pipes. However, I tend to believe the makers if they don't make provision for changing the fluid - it's likely to be just a waste of time and money.

Changing engine oil is a different matter. It gets contaminated by the products of combustion. Not so in an auto - the only reason to change it is if the molecular structure of the fluid breaks down in some way.

The message from "__ __" contains these words:

Very unlikely.

The message from "__ __" contains these words:

Yes and no. There's a lot of mixing goes on in a torque convertor - and that means that to get out a reasonable proportion of the old oil you'd have to replace more then the total volume of the system. Depending how thorough you wanted to be several time more.

The message from Dave Plowman contains these words:

Sorry, Dave, I didn't mean you - I meant "you" in general.

Hi Chaps,

When I check the dipstick it shows reddish liquid quite a way above the "full" mark. Its not brown or discoloured in any way.

The funny thin is this: I just took the van out and it was a pig for the first mile, but then behaved absolutely OK. Obviously I am anxious to avoid a potential £1500 bill if I can.

Cheers - Adam

Good point.

I guess I was just theorising as to whether some minor contamination could occur, that may not have much impact on the autoboxes performance, and a fluid change / flush would help with.

But I see your point, once something has occurred to cause the contamination, the damage there is likely to simply continue.

And as you say, ATF, these days, can be quite expensive.

Again, good point that I hadn't considered. The pathways can be quite intricate and small, and as you say, it's pressurised.

Do you mean just general debris as your changing the pipework back?

Well two things to consider, there - I guess the manufacturers would be mainly concerned with anything going wrong during the warranty period. And anyway, may consider the lifetime of their autobox to be a notional 100k miles.

As an example, the official servicing schedule for my car, is that the ATF doesn't need changing. Yet the service schedule specifies that for commerical driving, taxis, and other extreme scenarios, a 50k ATF change period is advisable.

I'll accept that the doomsayers tend to be a bit negative about the subject, and it's a fluid that isn't (or at least shouldn't ;-)) be subjected to a combustion environment. But it still has to withstand the rigours of heat, and any swarf or other debris that occurs over time.

My car has a little over 150k miles on the clock, and the original autobox. I don't baby it, but have had ATF changes (changes, rather than flushes, so they probably only changed a few litres of ATF) done at 85k and 135k (not because of any issues - merely because I bought it with 80k miles on the clock). So I'm following 50k changes for ATF, as a general precaution and hopefully prevantative measure, because I hope to get as much life out of it as I can. As it stands, there's no slippage, nor any roughness, so it may be a little overkill - but the fluid stays looking in a healthy condition, and the autobox performs as good as it did when I bought the car.

But I see your point, in general - autoboxes have improved in many ways in recent years, and better manufacturing, and software control, and better ATF probably goes a long way to improving their service life.

Well I've seen procedures on websites for doing this, and comments from those doing it. And from what I've read, they probably used a litre or two more than what should be the total contents of the gearbox and torque converter, but then it all ran clean and red.

I'd buy your point, though, that your unlikely to replace _all_ the old, with the new - but the people who do this, tend to carry on catching the old, and filling in the new, until what flows is clean and red.

And it can be a little tricky with the catching, the filling, and stopping the motor - but I think it's a reasonable method for the DIY user.

Then it's unlikely to be contaminated.

But don't be too concerned about it being cherry red, though. It's just a dye, that does seem to break down after a while.

Darkness, and a sort of burnt smell are things to concern yourself over. If it's just sort of a red / brown colour, that's not any particular hint that it's in need of being changed.

As Guy pointed out in another posting - the procedure for actually checking the level tends to be a bit convoluted. It's normally something like after having driven the car for around half an hour, stop, put it in park, make sure the handbrake is fully on (and footbrake too, if you're paranoid ;-)), move the gear stick slowly through all the positions (slowly enough so that you feel the gears engage, when they should), and back again to park, then wait a couple of minutes with the engine running, then go and check the dipstick.

It's unlikely to be overfull, unless somebody has been messing with the ATF, recently, or something else is getting in there - in which case there would likely be some evidence in the condition of the ATF.

I'm no particular expert on diagnosing autoboxes, but you seem to be suggesting that it runs OK when the ATF is up to temperature. I suspect Dave or Guy may have a better understanding of what that implies, than I do (I know my limitations ;-)).

The message from " Adam Lipscombe" contains these words:

Are you checking the dipstick in the way described in the manual? Autobox's dipsticks almost always read high unless you follow the instructions.

I agree with Fred. The symptoms sound like the valves which control the hydraulic fluid flow are sticking, possibly because of crap. Personally, I'd drop the valve chest at the bottom of the box ( I'd hope), throw away the fluid, clean out the oil ways and valves with a high pressure air line and a chlorinated solvent. Then I'd re-assemble with new fluid and see if I'd solved the problem. Auto boxes are not that complicated, provided that you have some patience and a basic understanding of the operating mechanism. Go away to the library and read up the subject a little before you start. If you read up on any 1970-80's auto box, you will find the list of likely faults and the cures. Alternatively, hunt for a breaker with an equivalent box and fit it.

Regards Capitol

I suspect that this may be the four wheel drive version of the Ford CD4E autobox (certainly some of these vehicles are fitted with this 'box for the US market). They suffer a catalogue of faults, including faults with the lock-up clutch. I think first of all you need to positively identify the gearbox and then seek expert advice. Ring Alan Bilby at FATE (Federation of Automatic Transmission Engineers) HQ at Southend when you know what 'box you've got. He may then be able to recommend a repairer who has the relevant experience. If its a sticking valve in the valve body then a change of fluid may help - the detergent action of fresh fluid can free off the 'varnish' that builds up in the valve bore. I have had this lead to success a couple of times - especially on ZF 'boxes.

I think the man with the smart arse sig is well versed on the auto box, but I see a lot more imports than most as two of my account customers specalise in Jap imports. I have seen loads of imports with dammage caused by being forklifted out of the container they were shipped in, if your Bongo had been treated this way then it may have suffered some dammage to the transmission or plumbing . If it had lost any fluid then someone could have refilled the gearbox with the wrong spec (and ammount) of ATF, bearing in mind the cost of changing the ATF against the cost of servicing the G/Box it has to be worth a go.

Damage. One M.

Dave Baker - Puma Race Engines

In article , Fred

This would certainly be worth a try, but, let's face it, it's probably beyond many, although as you say there's no need for it to be. Few, if any, normal *garages* will even open up an auto - except possibly to replace a downshift cable if it had one.