hixonium

Ok, I've done some searching through this forum regarding "no overdrive", but I've found none that directly address my specific problem. So let me give you the facts:

1. 1994 ES 300 161,000 miles, just purchased

2. Has tranny fluid ever been replaced? Don't know. Fluid does have some red in it, but also some brown. Does not smell burnt.

3. I can't get an accurate reading on the tranny fluid dipstick, even when up to temp, and engine running. It is above the HOT mark, though.

4. IMPORTANT*****The O/D light is not flashing, no CEL.

5. When I disconnect the negative cable from the battery (at least 10 minutes to reset ECU), and then reconnnect, I can drive it down the road a way and it WILL shift into O/D. But later on it will downshift to 3rd, then upshift to O/D, back and forth, back and forth a few times, finally remaining in 3rd. BUT I can disconnnect the nagative cable again to reset ECU, and O/D will come back for a little while.

6. It all seems to revolve around the ECU to some degree. If so, is there a solution that is reasonably priced? Like getting a remanufactured one? Or having mine rebuilt?

7. Or do you think that I might have the tranny drained and refilled? It's obvious that old fluid can cause shift problems. Could this have been the solution the whole time?

Regarding point 4, my guess is that no codes have been triggered by this O/D symptom, so I'm thinking that the problem could be outside the tranny. By this I mean that the tranny is not being commanded to shift to O/D. Does the ECU send that command? I'm also aware that there is a computer in the tranny, but what does it do specifically?

I've tried to be thorough with the details. Hopefully someone out there has some ideas.

LeX2K

I would say the first thing you need to do is at least do a tranny flush, even better if you can drop the pan and replace the screen/filter. Some people will tell you to never flush the fluid in an higher mileage transmission (I personally think it's silly) so if you want to be extra safe, just do a drain and fill, which will be about 2.5 liters. You can then do a drain and fill 2-3 more times in the next week or so, which will remove most of the old fluid.

Your issue sounds to me like either a fluid level problem, or a shift solenoid issue. If it does turn out to be the ECU, you should be able to find a replacement on Ebay for a reasonable cost. The ECU does not often fail, but it has been known to happen.

I'm not sure what you mean when you say you can't get an accurate fluid level reading, why exactly? Another question, when the transmission drops out of OD, does the OD off light come on? BTW, the ECU determines how the transmission shifts, every gear all the time, it is not done only hydraulically like transmissions used to be. For example, you can drive 80mph and shift the tranny into 1st gear, but the computer will not allow it. On an old school transmission, it would try to go into first gear.

...forgot to say, I don't believe the ECU in your car is a "smart" computer, meaning it does not retain anything when you turn the car off. It does not learn driving patterns or any other driving dynamic, so I don't believe there is such a thing as resetting the ECU. Someone can correct me if wrong here. So you "resetting" the ECU may simply be the fact that the transmission has a chance to cool down, or components in the computer are failing after a time so stopping the car gives them a chance to cool off and start working properly again.

hixonium

The dipstick gets wet well above the HOT mark. I can't tell if this means it has too much fluid or not. But I am taking this reading while the engine is running.

The OD off light does NOT come on when it drops out of OD. Again, no flashing OD off light, no CEL.

If it is a shift solenoid issue, where is this solenoid?

LeX2K

The solenoids are inside the tranny, not sure exactly how much is involved in getting to them on this particular transmission (I am not a tranny expert and will avoid working on them if I can help it). I did replace a shift solenoid on Corolla transmission once and it was pretty easy, I doubt it would be all that hard on the A541E.

It sounds like you have way too much fluid in the tranny, drain about a liter of it out, go for a drive then check again. It should be right at the top of the HOT line after 10-15 minutes of steady speed driving, above 45mph.

hixonium

In your experience, do you think that if it were a solenoid issue, that it would NEVER jump between OD and 3rd, and just stay in 3rd? Or can a solenoid intermittently fail and cause my issue? And fail based on tranny temperature?

LeX2K

I took a quick look at the service manual, you have to remove the valve body to get to them, which is not the easiest thing to do. The hard part is removing the oil tubes, well it's easy to remove them but much harder to remember where they go back! According to the manual, the computer will flag a code if one of the solenoids it not working properly, there are 3 solenoids in total. If I'm understanding the manual right, it can store a trouble code even if the O/D light does not flash. Question is how to retrieve that code.

BTW, there is a way to test the transmission to see if it mechanicially sound, but it does not apply to the overdrive unfortunately. What you do is disconnect all the solenoids, and drive the car while shifting the transmission manually at speeds less than 30mph. If it shifts through all the gears properly, then the problem is electronic.

LeX2K

Temperature failure for sure I've seen that, fluid gets hot and the tranny starts to act up. Bad fluid level can cause all sorts of problems, you can't proceed until you get the level correct.

But the O/D system I don't know how that works exactly, like I said I'm not an automatic tranny expert, it is in fact my weakest bit of knowledge when it comes to cars. To answer your question, solenoids can fail intermittently, especially the connectors and wires going to them.

If you want to read though the manual, you can find it online here:
http://www.scribd.com/doc/6004125/a5...atic-Transaxle
Or get the .pdf
www.turboninjas.com/camry/ax2.pdf

hixonium

I'm going to take it in to address the fluid tomorrow. The fact that it has too much fluid may suggest that someone put more fluid in the tranny without draining it first. I hope he/she did not put in the wrong type.

LeX2K

According to the manual, a drain and fill is 3.5 liters, but I've never been able to get that much out of these transmissions just by removing the drain plug, so you will see a bit less. If you measure what drains out and you see more than 3.5 liters than the unit was definitely over filled.

Keep in mind that your car has a separate drain for the differential. You don't have to drain the differential to get your fluid level correct, but at some point you should drain the differential, otherwise fluid tends to stay there.

hixonium

UPDATE:
I took the car to the local Toyota dealer, and they confirmed that the tranny was overfilled. The tech drained and refilled it to the correct level. The OD worked for several miles, about 15-20. But later it kicked in and out of OD until it finally shifted no higher than 3rd, just like the previous symptom. The difference here is that no one disconnected the negative battery cable, as I was doing when I was thinking that the ECU was a possible culprit. I initially had OD for several miles this time. Now, since I found that the tranny was overfilled, I'm thinking that whoever decided to add more fluid probably put in the wrong type. An incorrect fluid will cause shift issues, right? Doing this drain and fill today probably got rid of some of that fluid, but not enough to completely eliminate the "no OD" permanently. I think that another drain and fill or two will go a long way to fixing this problem. The only other solution would be to flush out all the old fluid, but not many people in this forum like the idea. What do you guys think? Should more drain and fills be attempted?

LeX2K

My feeling is there is something wrong with the transmission. But get yourself the most inexpensive Dexron III fluid you can find and do 3 drain and fills (drive for 10 minutes between changes), if that does not correct the problem then you will have to diagnose further.

hixonium

That will, in effect, be a "flush" of the tranny without using any flushing chemicals. The good thing is that the Toyota tech did not find any particles, metal or otherwise in the pan. Since I got better results from the drain and fill yesterday, I think I'm going to do more drain and fills, as you suggested. Trying to keep positive here.