All - automatic transmissions - peter moss

Iv been driving automatics for decades so had my share of problems but learned early that the fuid does not last for ever ,a lot of people seem to think it does ,

As far back as the 60s a service did not include changing the fluid and these days its still not part of the service as units are either sealed for life or as the manufactures say, or in the case of renault when it breaks and we fit another unit it will have fresh fluid ,

Transmission fluid should be changed at or before 30,000 miles ,yes your going to say but its fully synthetic and there is no mention in the hand book about that ,point is if you change the fluid or better still flush it you get most of the muck out that blocks up the valve body and the screen filter inside ,

the majority of todays automatics dont have dip sticks they have level tubes up inside the drain plug that have to be taken out just to drain them ,and you need to drain them from hot put the level tube back in and then find the fill plug and with the engine running in neutral and at appx 60 deg pour the fluid in untill the fluid starts to run out of the drain / level hole , thats if you dont have to take the pan off ,some dont have drain plugs ,its messy and you do have to know what you are doing but if you dont know what your doing get the dealers to do it for you your transmission will last a lot longer !

All - automatic transmissions - RT

Conventional torque converter + planetary gears are the ones that have no specified maintenance - not sealed for life as they aren't sealed even if the don't have a dipstick.

Even where recommended, the interval varies depending on whether the vehicle use is classed as "extreme conditions" and that definition varies considerably by brand.

Drain/refill only changes about a third of the ATF because of the amount retained in the torque converter and valve chest.

The primary advantage of a dipstick is to see the colour of the ATF - translucent red is fresh - opaque red is normal - brown needs changing - black is too late!

All - automatic transmissions - peter moss

Renault marketed their AL4 as sealed for life years ago ,dip sticks primary use is to check the kevel of the fluid , units where you have to take the pan off are classed as sealed for life as the average person does not have a clue where to start systems like this are deemed dealer only ,Honda baxi auto trans on 1999 was sealed unit with all of the failures it only lasted to 2003

The filter was sealed inside the unit you would have to take the unit apart to get to the filter ,there videos on you tube to substanciate this , what the comment was trying to put across was that the fuid does not last for the life of the vehicle

These systems are designed for the vehicle to be taken into the dealers in the advent of limp mode due to the complexity of modern vehicles there often no reference to problems other than to take the vehicles into the dealers ,

The only reference in the renault hand book to the limp mode is you spent to much time in traffic or to long on the motorway or you have been carrying /towing to much weight [Modus manual ]

the fact that there is a fluid condition sensor in the unit to monitor viscosity and temp means when the fluid looses its viscosity it will flag limp mode

On certain applications of PSA vehicles there is a digital counter in the transmission software software that counts upto 32000 miles and then flags limp mode [citrone training manual for dealers ]

i hope this clarifies the reason for stating sealed for life ,as far as the owner is concerned its sealed !

All - automatic transmissions - edlithgow

"the fact that there is a fluid condition sensor in the unit to monitor viscosity and temp means when the fluid looses its viscosity it will flag limp mode"

Could you say what models have this fitted? Curious to know how it works.

My first thought was it might be possible to use a scrap one as an oil condition monitor, but I'd guess it'll be highly intergrated into the onboard computer systems and that wouldn't be possible, at least not for me.

I did a search for "ATF fluid condition sensor". Mostly just got references to a temperature sensor, but also turned up this scarily complex description, which goes into the basic principles in some detail.

It's a patent application, so I don't know if its actually implemented in anything.

All - automatic transmissions - peter moss

OH ok then the Al4 unit has what Renault call a condition sensor fitted in the bottom ouside of the case the unit it mesures the heat/vicosity of the fluid starting from the known cold vicosity of the recomended fluid this read by the computer that will trigger limp mode if it reads the fluid is to hot/ thin = lower preasure , the sensor is made by Delphi i have 3 secvice traning manuals covering diferent applications and software of the units for PSA France covering Renault / Citrone /peugeot !

you can find one in an automatic modus /senenic /megan /Clio but they are a just a heat sensor basicly bit expensive at arond £65 but you might have to check the price out though plus they are appx 20mm dia !

Edited by peter moss on 15/01/2017 at 21:13

All - automatic transmissions - gordonbennet

I'll be changing the oil on my Landcruiser autobox in the spring, thats one of these you have to have running at a certain temp and check the level via a level plug at the bottom of the sump where you would expect to find the drain plug when car designers still had some common sense...oh and i shan't be paying for oil made from angel tears from the maker, i've found good quality equivalents of the new synthetic oils at sensible money by the 20 litre drum, enough for three sumpfulls over the course of a week.

The previous LC's were a doddle, proper dipstick and you'd refill the box through the dipstick tube, Scooby Outback is the same, so i'm thoroughly disappointed that Toyota has seen fit to join other makers and designing that excellent 'can be fixed in the field' simplicity out.

Scooby take the gold medal mind, third dipstick under the bonnet for the front diff, now thats what i call engineered to last.

Every time i've changed gearbox oil, manual or auto, there has been a noticeable improvement in the box.

The modern trend of non or extreme long life servicing has led people to replace their vehicles sooner to avoid eye watering repair bills, so the designers are fulfilling their roles as money makers for their employers admirably.

Edited by gordonbennet on 13/01/2017 at 20:37

All - automatic transmissions - gordonbennet

In my previous work i was under a lot of new cars every day, during the fashionable period for so called sealed for life (or 100k if you're lucky) autoboxes, well lots of cars and expensive 4x4's with not the best reputations for reliability did indeed have stickers/plates on the underside of the gearbox stating either sealed for life or non serviceable.

All - automatic transmissions - peter moss

you must be old school your right look through most hand books for automatic vehicles and anything to do with the transmission is dealer only , and yes i found another make of fluid for the renault i checked the numbers on the back of the container you could put in VW /Honda ect same spec and half the price ,

i flushed my transmission out filled with fresh it drives like a good auto should a lot smoother than before , back in the day i bought an American AMX 304 V8 no forward or reverse dropped the unit and stripped it the clutches were gone i rebuilt it with ford capri clutch plates and spaces [same size ] plus a new seal kit it ran well they did not have the problems auto units have to day , i also use extra magnets on the oil pan just in case there is any metalic bits floating around same on the oil filter .

All - automatic transmissions - John F

Beware. Disturb them at your peril. I once read a post from an experienced American auto mechanic saying that problems can arise soon after a (probably unnecessary) fluid change. And I have just read the following on another site...

'If you just replace the fluid that's removed when dropping the pan, the detergents in that new fluid can cause any gum/sludge/varnish inside the transmission to become suspended in the mix of new and old fluid. And if any of that debis finds it's (sic) way into the valve body of the transmission, that's when the transmission fails.'

I have never seen a good enough reason to depart from the presumably truly expert 'sealed for life' advice from ZF about the boxes I have had, none of which have ever given any trouble. For autoboxes, I think the old adage 'if it works don't mend it' is particularly appropriate.

Those with a vested interest in generating 'service' work might disagree.

All - automatic transmissions - gordonbennet

I think the idea is to change the transmission oil before you need to dig it out with an imperial chisel or trowel, hence no worries about sludging up and clumps of goodness knows what flaking off and going round the innards, just like good preventative servicing on any mechanical unit.

Cost of good preventative maintenance, especially if you DiY and buy quality alternatives in bulk, is but a tiny fraction of the unit costs should they fail.

Landcruiser 5 speed auto box, how much?, probably £3k at a guess maybe £4k by the time its fitted and filled with a Angels tears, as against 20 litres Dexron6 around £70, why on earth would you risk it.

Plenty of online reports of autoboxes on British and German luxury 4x4's packing up around 100k unless the recommended no service requirements are sensibly given a good ignoring.

Edited by gordonbennet on 15/01/2017 at 21:49

All - automatic transmissions - edlithgow

NCKU Library was selling off some redundant textbooks, and I snagged a couple of big autotransmission manuals for next to nothing.

One of them has beautiful multi-coloured fold out diagrams of awesome complexity.

I'm quite glad I've got the book, but I'm very glad I don't have one of those transmissions.

All - automatic transmissions - RafflesNH


"dig it out with an imperial chisel or trowel" and " filled with Angels tears"

...oh I did have a good larf! ;-)

Thanks for brightening my day.

Edited by RafflesNH on 18/01/2017 at 15:03

All - automatic transmissions - Brit_in_Germany

Not sure where the concept of "'sealed for life' advice from ZF" comes from. Their recommendation for changing the fluid on my 6HP26 transmission is 80-120,000 km dependent on usage conditions.

All - automatic transmissions - peter moss

If it aint broke dont fix it relating to auto units does have a grain of truth in respect of if the fluid has not been changed for a long period the debris from the clutch packs [friction and steel spacers ] builds up in the fluid adding to the viscosity so if the fluid is then just changed but not flushed it will leave the residues from the friction /steel spacer pllates in the system when the new fluid is put in it will disturb the particals and they can build up in the valve body and can cause problems , if you take a valve body off a unit after prolonged use you will see what looks like a graphite coating when you take it apart and thats the residue build up from the clutch packs ,if the unit does not have any problems it may well function ok until you put fresh fluid in it ,debris from the clutch steels will just wear down any O rings as it is abrasive , for my part when i change the fluid on my vehicle i flush the unit out first and with a clean drain pan you can see the debris come out proof of the pudding is to put a magnet into the fluid and see whats sticks to it ,i dont think i would like that stuff pumping around my unit for 80,000 or more .

i expect there are videos on the youtube showing you what 80000 plus miles trans mission fluid looks like but for me i change mine at 30,000 ,look at any information relating to working on these units and they will state that conditions have to be absolutly clean /sterile ,fluid is subject to condensation /sludge and debris from moving parts valve body spools can start sticking if the sluge /debris in the fluid and in the case of the Honda baxa small valve body ports such as the converter lock up feed can become blocked !

OK thats 2 pence worth !


Ask Honest John

Value my car