This raises the question of whether changing the fluid extends the life of the transmission or not, apart from the issue of which fluid to use.

I don't have the data sheet on the Valvoline MaxLife. Does it say that it is certified to the spec by ZF? Or does it say that you should use it in applications that call for that spec? That is at the core of the confusion caused by the marketing departments of the oil companies.

I do see that Valvoline have some fluids that are certified to various specs (so they can certainly do it if they want to) and some others that aren't (but which are usually cheaper).

Edit: I looked up the list of suppliers to ZF for their Lifeguard 5 ATF. Valvoline isn't on the list. There are 23 suppliers listed. The document is from 2009. Interestingly, there is a Castrol approved fluid listed. It was Transmax Z (presumably for ZF). I only see references to it being available in Australia now, and there it no longer lists the ZF approval on line. It shows as a Dexron III fluid. Perhaps it was reformulated, I don't know.

I suggest that causing that confusion is exactly what some of these oil companies set out to do. You only have to see that they certify some fluids and don't certify others, but try and suggest that they are the same. Marketing. The job of the marketing department is to get your $$.

Remember that this is a proprietary standard, not a public one. It isn't like you can get it tested by a third party and claim compliance. So they don't claim to meet the standard. They just say that it is good to go. Trust them.

None of that means it is a bad fluid. The issue I have is that ZF says that their transmissions require different fluids for their different designs. It costs them money to move to a new fluid, they don't do it just for fun. They don't require you to buy the fluid off of them, just to buy a certified fluid. You can buy it from any one of the oil companies licensed to make it. But they do note that it isn't Dexron. ZF should know, they make a lot of transmissions that use Dexron III. Castrol was a supplier to them. Castrol says a Dexron fluid works fine in a ZF 5 speed automatic. OK. They can't certify it apparently. Just think how much money Castrol could make if they could come up with a single fluid that could get certified to all the ATF standards. They would clean up. I wonder why they haven't done that.

All that aside, TiAg had good luck with that fluid. If it is still the same fluid as when he bought it, then there is a good reference for you.

did, not find that data sheet on the net, but of course is not on the zf chart, i also got this:
Castrol 03521 Transmax Import Multi-Vehicle Automatic Transmission Fluid, to do a change ,as i have some slippage 1-2 when hot,as i described
in my other tread, i may change the "transmission thermostat thats attached to the radiator (here,nr#15),as one shop said ,if that does not work properly it will make the tranny run to hot and start slipping!.

Now, anyone knows how to test those "output speed sensor" from the inside tranny? with a multimeter ? to see
if is good or bad?, nr-6 here..

Thanks,

If BMW had put a proper 3 pedal trans behind the V8s in the E53, ATF would never have been a topic I would discuss. In over 30 yrs of driving, this is the first slushbox vehicle I have owned. 60s/70s muscle cars, Hondas, Audi Quattros, Jeeps, Vettes, Vipers, BMWs (except the E53), all manual trans.

I am coming from an 06 350Z nightmare. The only part of the car I didn't have a problem with was the 6MT.

I loved Z cars but will never buy another Nissan thanks to their horrible handling of the VQ35DE REVUP issue.

Hell I am just glad and lucky I have a 3 pedal 6 cylinder, if the E53 was a V8 only car I highly doubt that they would have even offered a manual trans on it. Sad, really, when you think about it.

It isn't for everybody, but for us the alternative was the E83. 3.0si, 260 hp, 6MT, better shifting than the E53 manual, better 0-100 km than the E53 4.4 (600 lbs less curb weight). More cargo space than the E53. Towing limited to 3500 lbs. And then there is the whole status thing.

IMO-With all the confusion about what is a proper fluid for what transmission, the cost of repair, the camps that say it is good to do so verses the horror stories that it wasn't, the usual mix of new and old fluid rather than changing the fluid in the torque convertor, I don't see any logic in using anything other than the exact fluid that was originally loaded in the transmission.

That is not to say others haven't made a good choice with excellent results. I haven't seen a long list of folks that endorse a particular fluid in a particular transmission to have enough verification that fluid is as good or better then the original fluid. This thread may help some but my interpretation is that the primary reason folks have gone to other fluids is that the original fluid is so costly (I agree). They are way to proud of it--but

I suppose you could run the vehicle on jackstands (very carefully....) and read the signal at the connector on the outside of the transmission. That would tell you if there is a signal from the output speed sensor. I think it is a sine wave, so it is either going to be there or not, you aren't going to have an inaccurate reading IMO.

But really, the message you are getting (as I recall it) had to do with a problem with the output speed sensor reading. The computer reads the input speed and the output speed, and compares them. If they are too different, it says there is an implausible reading. It doesn't mean that the sensor is faulty, just that the sensor isn't reporting what the controller expects it to. The most likely cause for that is that the transmission is slipping. And you know already that it is, both from the driving characteristics and from the burnt fluid. So I wouldn't think that the output speed sensor would be a cause, rather an early warning that slipping has started. But you already know that.

There are tests for the solenoids that activate various circuits. But you are only checking electrically. The transmission is a mechanical/hydraulic/electronic system. All the monitoring and faults are reported electronically. But that doesn't imply that the root cause is an electrical fault, as a mechanical or hydraulic problem will show up as an electrical fault (symptom vs cause).

Good luck.