Help ::: 98 740IL Transmission Prog Fault

"zzz" wrote

It's 2nd gear, I believe.

It's "limp-home mode"

If it doesn't reset upon the restart after key being off for a few minutes (or it immediately goes back into limp mode after a restart), it's completely broken and you will need a rebuild or new transmission.

FloydR

Third I think.

Depends what is wrong. Sometimes a stuck band or whatever will free off on overrun or by going into reverse and then out again.

Mine very occaisionally gives this fault after long downhill runs in hot weather if I then 'feather' the accelerator (and there is a slight clunk when it gets confused about whether it is changing up or not). The rest of the time the gearbox is fine.

It will go into limp home mode if the voltage to the gearbox is low, so the first thing to check is the voltage at the battery with the engine running (should be 13.8) - then any connectors in the loom to the gearbox for high resistance.

I disagree - it's almost certainly an electronics, not mechanical - fault.

Well, it was not "resetting" after shutting it down. It is at the dealers at the moment .. should find out today.

I shall update the newsgroup.

Thanks to all who chimed in.

For very selfish reasons ... I would "like to believe" it is electrical and not mechanical. We shall see.

Cheers.

Well, limp home where all you get is fourth, neutral, park and reverse is initialised by the electronics shutting down totally. It might be thought an unusual mechanical fault which could guarantee this, although of course not impossible, but I can't think of *one* mechanical fault which could bring this about - it would need several. So if your dealer tells you you need a replacement box, take it to another for a second opinion before spending out. A code reading might also make sense.

The verdict is in ... NOT good news

1. Appears to be a "mechanical failure not electrical" says the reputable local BMW dealership

1. Sealed unit ... dealer cannot repair

2. Rebuilt unit + labor =00 (OUCH)!

1. Towed is home to sulk over it!

2. Car has 153K miles and in overall very good condition; new tires; new brakes/rotors ... but 00 ... I LOVE this car otherwise !

1. Think I can get about 4k or so on my taxes if I "donate" the car to charity

2. Have to pause and think my options through.

1. Any advice???

Thanks in advance.

car-part.com says this tranny ranges from $400 to $2600 with lots inbetween.

If you do a little Googling you should find a mechanical flow chart showing what does what on an auto box, and what the symptoms of the failure of each component are. For example, the failure of the pump results in no drive in either direction in any gear. Failure of the various clutch packs and brake bands similarly effects the operation of some gears, but as I said before I can't think of the failure of one of these which would leave 4th, neutral and reverse needed for the limp home mode still operating normally - this is a symptom of electronics failure.

It's not sealed. Nor is the dealer an 'expert' if they can't repair it. It is simply uneconomical for them to do so with their high labour charges, so they don't employ technicians who understand them.

Of course many will recommend a fully rebuilt box rather than just fixing the actual fault. In general this is good practice if the failure is mechanical, but not necessary or even desirable if it is electronic.

What you need is a specialist who understands these boxes. Finding one in your area may not be easy, though, unless others here have a recommendation.

Is it anything like if the computer detects anything wrong it just shuts down? I.e. a small fault might occur but that triggers the computer to shut down the whole system?

Dealers will hook the car up to the diagnostic system and then say "computer says no". That is if they know how to do that properly or indeed want to do it properly. Did they offer to buy your car from you at a knock down price?!

Like Dave says BMW don't make the boxes and don't support their repair (or maintenance in most cases) It's like buying a PC at PC World and expecting them to be able to fix a power supply fault.

If say your alternator dies, and you continue driving, one of the first symptoms you'll notice as the battery volts drop is the gearbox goes into limp home mode. It could be the solenoids need a full '12 volts' to operate efficiently, so this is why it shuts down earlier than other electronics on the car.

The computer is anything but infallible - and that's assuming the dealer told the truth about the findings.

Mine also farms out AC work and body repairs. Weird, really.

In that case it's simpler to just fit a new supply as the labour cost to fix it is likely to exceed it.

Not so with an auto - although it might be at main dealer labour rates if a full recon is needed.

I've not had a modern ZF apart yet, but I'm told the valve chest and internal electronics are accessible without removing the box.

I have two recommendations for you, one controversial, one not.

1. Top post. Bottom posting is for idiots that can't follow a thread. Top posting is for people with at least half a brain that can follow a thread, and therefore get pissed off at having to scroll down through a bunch of already read garbage to get to new info.

1. Find yourself a good BMW independent. Try
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   for locating one. They'll be more realistic than the dealer's "time for a new car" response.

Brett Anderson KMS- Koala Motorsport

One could also argue that the "problem" with bottom posting you mention is really caused by people too lazy to trim included material to the barest minimum required to retain context. This is an age-old problem on usenet.

Yes, the problem is best summed up as a combination of not only top posting, but the failure to edit for context. The latter part is the subtle part, and the one that yer typical top poster doesn't understand. Oh well.