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Old 10-19-2006, 02:21 AM   #1
toml
 
Join Date: Jun 2005
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Default Auto transmission not engaging...

Hi all,

I tried reading up on how an automatic transmission worked, so I could work out what is wrong with mine, but without actually having one in front of you to play with made it extremely hard to understand

There's two main issues with my A340e:

1) Occasionally, when I put it into gear (normally it happens when I shift from Park -> Reverse), it doesn't seem to actually engage the gear - the car revs freely and does not move anywhere.

2) Shifts are hard. Shifting in and out of 2nd gear is the worst, its a big 'jolt'; doesn't seem to be as smooth as it should be.

Based on my very basic knowledge of an automatic transmission, I would assume that there's something wrong with the hydrolic system, causing it to not engage the gears? Perhaps the solenoids are worn / faulty?

I've run the ECT ECU diagnostic but it returns no codes.

Am I on the right track here, can someone point me to what pieces of the transmission could be causing such problems?

Thanks,
Tom
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Old 10-19-2006, 03:28 AM   #2
Nick M
 
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You really need the A340E flow chart. It shows what is applied or held in each gear and of each range.

But I would start with fluid. Slippage is often from being low on fluid. Is your car marking its territory?
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Old 10-19-2006, 05:20 AM   #3
toml
 
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Heh, I like that metaphor. No, it's not marking it's territory... I'm about to change the fluid in it so I'll see if that makes any difference.

So is 'slippage' my problem here? That seems to insinuate that there is at least some friction between the moving parts, whereas in my case I often feel no friction at all.

This flow chart you mention, is it the troubleshooting flow chart in the TSRM, or something else?
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Old 10-19-2006, 01:36 PM   #4
jetjock
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Don't feel bad tom. Autos can be complex pieces of machinery and without pulling one down can be difficult to understand. As with all machines breaking them down into subsystems helps to conceptually grasp how they operate. They're not all that hard though. Lots of places on the Net to help you understand.

Your symptoms could be caused by many things but a glance at my A340E book diagnostic chart shows they could be caused by incorrect line pressure or an incorrectly adjusted throttle cable. Shift shock is usually associated with line pressure problems so have it checked and be sure the throttle cable is adjusted correctly

Nick is right: Before you do anything start with the fluid. The fluid not only "drives" the transmission but also cools and lubricates it. An automatic transmission is above all a hydraulic system. The secret to increasing the longevity of lubricating fluid and the system it's used in is to keep it clean and cool. This is especially true in hydraulic systems. Contaminated fluid and heat are the single greatest killers of them. The situation is made worse in cars because as the clutches and brakes operate they shed friction material into the fluid the same way a manual clutch sheds it's friction material over time. The heat problem stems from an auto tranny being 10 pounds of stuff in a 5 pound bag.

Many times I've seen great improvement after flushing and fluid replacement. Course, it won't fix worn out parts. It may be too late but try it. You can't simply drain the pan because you'll only get 30% or so of the fluid out. If you do decide to go that way you should let the transmission drain overnight and do it 3 or 4 times over the course of a few days. Be sure to move the shift lever through every position to flush the entire valve body after each fill. You should also drop the pan and replace the filter if there is one. Not sure about the 340 but since it's an older model I'm guessing it has a screen in the pan. Also, if there's a magnet in there be sure to clean it.

The best way to replace the fluid is to take it to a shop that has a tranny flushing machine like a T-Tech. Or you can do it yourself. Disconnect one of the cooler lines and put a hose from it into a bucket and start the engine. Shut it off when the hose begins to spit air and refill with the same amount of new fluid. You'll have to do that several times until the fluid color changes or you've replaced the specified fluid capacity of the transmission. For a good flush run 1.5 times the specified capacity through it.

This may solve your problem but it's a crap shoot. That's why it'd be risky to use expensive synthetic fluid. You could try using non-synthetic and if the problem clears up do the process again with synthetic and call it a day. If a fluid change doesn't help you'll need to get the tranny looked at by a professional.

Lastly, think about installing a better cooler and for sure install a better filter....especially if you have the tranny rebuilt. The stock screens used in most trannys are jokes. There are inline filters available but you can always buy a filter mount, plumb it into one of the color lines, and use a good spin on oil filter. You can also use a real hydraulic filter. Imho the best setup of all and the one I use is on all my autos is to install a depth (bypass) filter. That said, a spin on oil filter will work great and beats the factory gravel strainer by light years. Change the filter every 40K miles.

If you're smart you'll also put a filter on your PS system. A decent one is the Magnefine. It's normally sold for trannys but I feel it's somewhat small for that purpose, at least for an initial clean up. Great for PS though: http://tinyurl.com/yed4wx

Course, you could drive the crap out of the car without doing squat to make it last, all while investing in oil of snake and other worthless products rather than proven maintenance principles. While the Supra community seems to be full of such people me thinks you can do better.

Anyway, good luck with this and let us know what you find.
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Old 10-19-2006, 06:54 PM   #5
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When you said it was spinning freely, that is what I was assuming to be slippage. It could also not be engaging period.

1. Make sure the range selector nut on the trans is tight. Maybe that is slipping, and it never makes it to reverse.

TSRM has an article about setting the selector switch correctly.

2.Hard shifting can be a learned trait. Check the throttle cable on the throttle bracket. The transmission throttle cable, not the acclerator cable. That and the fluid as already mentioned.
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Old 10-20-2006, 03:00 AM   #6
toml
 
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Thank you both for the responses.

I followed the steps in the TSRM for the range selector nut when I installed the trans/engine a few months ago, but I will check it again.

I've also checked the trans throttle cable (about 1 month ago), and readjusted it as it was slightly out. The car seemed to shift better once this was better aligned!

I'm going to take the car to a transmission shop this weekend and get them to do a full flush of the fluid and see whether that helps.

I'll also stop in on the way home tonight and see if I can pick up a new transmission cooler and a filter.

I'll let you know how I go!


Tom
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Old 10-20-2006, 03:55 AM   #7
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Hmm another quick question... This one's going to sound very newbie, so excuse that.

When you're at speed (say 90km/hr) and let off the accelerator, the car decelerates, pulled by the engine as the revs drop. (Is there a technical term for this?!)

Over the last 10 days, the car has seemed to do this at a lower speed than usual. For example, previously if I was cruising at 60km/hr and let off the accelerator, I would simply coast along. Now, if I let off the accelerator at the same speed, it seems to have a much more sudden impact (the car slows much more sudden and the nose dips). Vacuum gauge seems to drop right down to 24-25 inHG, which (I think) is a higher vacuum than it used to drop to.

Is this a transmission 'thing' too, or is it unrelated?
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Old 10-20-2006, 03:00 PM   #8
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Quote:
When you're at speed (say 90km/hr) and let off the accelerator, the car decelerates, pulled by the engine as the revs drop. (Is there a technical term for this?!)
Compression, with out fuel, the engine becomes an oversized air pump.

Quote:
Now, if I let off the accelerator at the same speed, it seems to have a much more sudden impact (the car slows much more sudden and the nose dips). Vacuum gauge seems to drop right down to 24-25 inHG, which (I think) is a higher vacuum than it used to drop to.
The torque converter should unlock. That will allow the rear wheels to be free of the engine torque. Maybe that is your hard shift also.
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Old 10-20-2006, 07:55 PM   #9
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I just read about how a torque convertor works. Does the torque convertor on a MKIII have a lockup clutch? Is that what you were talking about that should 'unlock'?

What I don't understand is what could be causing a torque convertor to malfunction - they don't seem to have much in them that could break.
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Old 10-20-2006, 08:15 PM   #10
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Yes, it is a locking converter. It is fairly simple in idea. Lock the engine and trans together for improved fuel efficency when not acclerating.

I don't have the EWD (or any manual) here. Of the top of my head, the trans ECU proably provides a ground path for a relay. The relay will activate the locking solenoid. I have seen a stuck solenoid once. Their 4Runner was stalling though. The customer would rev the engine then dump it into drive so it wouldn't stall. After the clown got tired of doing it, he brought it in. Toyota gave him a new unit anyway.

The most likely cause of a harsh shift in all gears is the throttle calbe is misadjusted though.
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