lyonkster

I would have never believed it either if I didn't see it first hand. I would have never believed that a low voltage issue can cause the tranny to behave like it's slipping or worn out. As you can see, it fooled several mechanics as well!

I cannot say that I understand the details of how this works, but my suspicion is that with a weak battery, the cranking process during starting drops the voltage even lower, so that when I put the car in gear and try to drive, there is not enough voltage for some sensor or actuator to do its job properly. That's all I can say, since the complexity of this electronic transmission and its interactions with the main ECU are way way over my comprehension level . The only weird thing is that I would have assumed that once the engine is running, the alternator is providing a full 14 volts to the system, so there should be no low voltage condition - but again, I cannot say that I fully understand this at this point.

But it seems that with these modern cars, you should attempt no repair before first confirming a good battery. I was really REALLY close to getting another transmission this time around, and I am thanking my lucky stars that the dying battery reared its head before I did that and wasted my money (and a weekend worth of work)!

Leon

3UZFTE

I agree, I'm glad that you've fixed your problem, but why have you needed to go through so many batteries? I can't imagine that a 430, which let's say is an 01' like mine, you shouldn't have to replace your battery at 27k... and again at 45k, and then again at 85k... I have replaced my factory battery once, and on mine and I have 133k, but I also haven't had any tranny issues. I am not saying they aren't related, but your battery should last for about 5-7 years, depending on the condition it lives in, so maybe in CA they go a lot more regularly than in MN.

The alt spins, with the crank, since they are sharing the same belt. The alternator is creating way more than 14 volts, however due to regulators it is reduced to allow the battery to charge and maintain the 12v source that powers all the cars accessories. I am just skeptical of either an alternator or a battery going out within 27k, and again at 45k, and again at 85k.

Just a point of reference, 12.6 is a full battery, >11.6 is a dead battery, mostly likely it will not turn the car over. And, I am no expert, I just work at the "stealership", and try to help people solve their problems.

2jzism

iTrader: (4)

Wow a bad battery can cause these problems in our cars?

lyonkster

A valid point, and perhaps an indication of something else I need to track down. Let's see, the first battery went out in '04, which makes it almost 3 years on the factory battery. Agreed, pretty lame, but not awful. The second battery (still Lexus) went out in '06, so even lamer. I replaced that one with a Costco battery. It lasted until now, about 30 months. The good news is it qualified for a free replacement (no prorate), so that's good. But yes, I might try to figure out why their logevity stinks. Still, I'd rather replace batteries every 3 years than transmissions .


That's kind of my thinking too, unless the battery voltage does not rise to the needed level for some reason until it is fully charged. Perhaps my alternator is weak. Anyway, I agree that there is more research to be done in this arena, but at least I don't need to replace the tranny!

SPL FREEK

that suks how the dealer is always trying to get in your pockets deep...

sakataj

iTrader: (182)

yeah im with u....i have been skeptical bout this since i read it. im glad your prob is fixed but the odds of the tranny, battery,alternator going out at 27k,45k,and 85k are just astronomically low

esolo98

iTrader: (5)

Thanks for sharing this valuable info, could save us some money in the future

lyonkster

Hmmm, that is not what I am saying. I am postulating that the tranny in fact did NOT go out at either 27k or 45k (when it was replaced by dealer), or now at85k (when the dealer recommended replacing it without doing ANY check or inspection). I am guessing that the current transmission, as well as the two that were replaced, had nothing wrong with them. I am also not saying that the alternator went out - it is the original unit, and is working perfectly fine as far as I can tell.

My contention is that on all three occasions, it was the dying battery that created the symptoms seen at the transmission. But it was the battery, not the transmission, that was at fault. While the mileage intervals between these battery problems are short, the mean time between failures was around 3-4 years, which is short but not unheard of for a battery. Also, there was a lot of corrosion/oxidation at the battery, so perhaps that contributed even more to the low voltage condition.

I agree, this all seems far-fetched, except that the car has not hiccuped once since the new battery was put in, and my google searches show that this phenomenon has been seen by others. Again, I am not one to argue with facts on the ground, which are that the tranny works like a champ now, whereas before the battery swap it was acting up several times a day.

We'll see if this "fix" holds up, but I am happy to have fixed it with a free battery replacement rather than sinking in $3500 and a day's worth of work. But I am not a masochist, so perhaps others (who are) would prefer going through with the transmission swap instead of the battery replacement .

Leon

sakataj

iTrader: (182)

all in all....im still skeptical but happy u got it fixed man

V8RdnLow

iTrader: (14)

Great work! I would have been relieved...

lyonkster

Thanks bud! Somewhere deep down inside I am still a little skeptical too (as in "this is too good to be true and how could the "professionals" have not found this"), but with every new day without the problem coming back, it's harder and harder to ignore the reality .

lyonkster

You bet! I am ecstatic .

99Aristo

iTrader: (19)

Glad you figured it out....as a mechanic I see low voltage or amperage current flow as a major problem especially in these newer cars with so many computers. ****, even my 1990 turbo crx toy car fell to a "new" yellow top Optime battery that was 2 months old and became faulty only in CCA, not volts.
Anyway, again, glad you got it before the trans got replaced again.

Mr.NA_T

Good find....

lexstocker

Wow, awesome find! I wonder if it'll work for my amp situation hahaha. First thing that came to mind was how similar this sounds to computer problem that needs a reboot to fix things