transmission gentle thump during morning start - Mazda MX-6 Forum
 
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post #1 of 10 (permalink) Old 1-22-13, 12:35 Thread Starter
 
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transmission gentle thump during morning start

On a colder day, when starting out in the morning, the auto transmission doesn't always engage for the first 5 minutes or so. I put it in drive. Sometimes the car doesn't move. Then if I put it in neutral, after a moment or two, I hear a gentle thump. After that, the car always moves when I put it back in drive. There is no more problem for the rest of the day.

Would this just be the torque converter still filling up with fluid in the morning ? I am guessing that is it. But if that is correct, why is there this gentle thump ? Is that just the torque converter having filled up ?

I am thinking all I need do is rev up to about 3,000 rpm for a few seconds in the morning before starting to move.
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post #2 of 10 (permalink) Old 1-22-13, 13:51
 
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Sounds more like the car isn't shifting into gear even though the shift selector has moved to another gear. What happens if you manually select gears 2 or 1? Do a PMX626.com search on the transaxle range switch.
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post #3 of 10 (permalink) Old 1-22-13, 13:56 Thread Starter
 
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So far it only does this the first 5 minutes of starting out in the morning.

Sometimes during the day if I go up a steep incline at lo speed, like a driveway entrance, I can feel some slippage, and have to increase the rpm.

The fluid level is right at the correct amount.

I am mainly wondering if this is a transmission problem where it is soon to give out - or can it just be the torque converter fins may be a little worn, and needs to spin fast in order to get the job done.
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post #4 of 10 (permalink) Old 1-23-13, 6:17
 
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Sounds like a transmission problem. Some of the MPVs have a problem like this and I believe in that case it's a cracked drum of some sort in the tranny. No harm in doing a drain and fill with new fluid.

1997 MX-6 LS
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post #5 of 10 (permalink) Old 1-23-13, 7:44
 
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I thought you meant it only happens once when selecting drive, 1st, or 2nd. If you have to increase the rpm to get the same power you used to have during an incline then yes it's likely the torque converter. Especially if it occurs in 1st and 2nd gear.
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post #6 of 10 (permalink) Old 1-23-13, 13:18 Thread Starter
 
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Can I drive it like this for a while, and then one day it will just give out and not move ? How long do these usually go before giving out completely ? It's been over 2 years since this symptom started, and only in 1st gear so far. Then can I just get a new torque converter, and keep the same transmission ?

It's hard to tell if the slippage is occurring on the highway, because the gears are shifting. It does seem that when the rpm's increase, it takes a bit of time for the mph to respond.

I had a previous Toyota with an automatic that just gave up one day while driving. I didn't know anything about cars then. They put in a whole new transmission.
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post #7 of 10 (permalink) Old 1-24-13, 6:32
 
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From reading about bad torque converter symptoms online, I haven't seen anything that sounds like your issue. The next time this happens, shift into 2 to see if you can move right away. I don't know how the mx6 is, but on other cars when you put it in 2, it starts in second gear (not first) to help with acceleration on slippery surfaces.

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post #8 of 10 (permalink) Old 1-24-13, 20:28
 
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The torque converter is what provides the torque from the engine to the automatic transmission. Without it you go nowhere. It's an automatic clutch. If that clutch is slipping then it will take a while to engage and get up to speed. There is no timeline on when it will completely fail. What is most likely to happen is one day you'll step on the gas and you'll notice that no matter how much you try to accelerate you won't go anywhere. You might be able to accelerate away now but in the future it will slowly become less and less effective until you don't go anywhere. Sometimes it will be accompanied by harsh metal ringing noise, a wobbly clunking noise, or uncontrollable shuddering.

Replacing the torque converter is pretty easy once you get the transmission and engine separated. It simply slides onto the transmission side splines then it gets bolted the flex plate. I have a video on removing the automatic transmission in the MTX to ATX swap project. The only difference would be stopping at the point of me replacing the ATX with the MTX and instead just putting in a new torque converter and bolting everything back together. It's definitely doable for an intermediate DIY'er, a beginner though I wouldn't recommend attempting it.
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post #9 of 10 (permalink) Old 1-24-13, 20:52
 
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Bad torque converters aren't always going to sound the same because they have many components inside of them that can fail. Fins breaking and getting slung around in there like a coin in a washing machine, grinding due lockup clutch (same as friction disc) material wearing down, bearings failing, teeth/cogs breaking, and so on. Here are some examples I've found for you that show just a few of the noises they can make when they fail.

This first one will show you how the welds on the fins can break after a life cycle. This is the early stages of a complete failure. Had this person left the car running it would sound more like the one in the 3rd video below.






If you watch some of my videos on the ATX to MTX swap you'll notice that when this guy does an inspection on his torque converter that the loose play in the converter matches what I experienced. Thankfully I didn't have the same noise because my internals hadn't blown in the converter yet.


Here's one where you can actually see the torque converter and hear the damaged internals getting tossed around inside of it.


and so on.... Sometimes they won't make any noise, sometimes they'll scream to high heaven. Not going to say every case is different but there are certainly plenty of different sounds and symptoms when it comes to a bad torque converter.

Here's where I drop my ATX and show the torque converter inside. Thing is damn heavy.

http://youtu.be/a8WuXoCSiaA?t=34m46s

Automatic owners will eventually have to replace the torque converter in the 626 and MX-6 it's just a matter of time. It's a relatively cheap fix though with aftermarket converters going for as cheap as $100 up to $800 for a dealership item. It's definitely repairable and can be accomplished by most DIY'ers given enough time and effort.
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post #10 of 10 (permalink) Old 1-29-13, 16:45 Thread Starter
 
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Thankfully I have none of these noises.

The experiment seems to working. If I rev to about 3,000 rpm for a few seconds before moving out in the morning, this problem has not occurred again. So I am guessing that before, the torque converter didn't get a chance to fill up with fluid in the morning before starting out. I still don't know what that gentle thump would be that would happen if I needed to shift to neutral.

That Toyota I had never had any noises. One day I just drove up to a stop sign. It just decided not to move anymore. I think I'd rather have a few warning noises, so you know it's time to get it replaced.
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