Jatco jerk / jump solution?

[wild_weston 0]

Hi all,

I came across the following tip for a solution to the jatco jerk.

Jacto jerk is on cars that use the jatco automatic transmission (mazdas bmws etc) and may jerk (or jump) when changing from 1st to 2nd. Jatco transmissions are generally fitted to japanese BMWs as standard.

I noticed this on mine, the transmission is perfectly fine so it is just something you get used to (ignore) as it only happens from 1st to 2nd and is usually only really noticable when cold.

The solution I read up on is:

Turn you ignition key to setting 2 (instrument lights come on but car isn't started).

Depress the accelerator all the way to the floor for 25 to 30 secs.

At this point you should hear a slight noise, this is the automatic transmission cpu resetting.

Then start the car (obviously take your foot off the gas first).

Apparantly the car learns your driving style over the next thousand Ks and sets itself to that. So if you are not the original owner it maybe that it is set to the previous owners driving style and that is why the jerk is occuring.

I read it on bimmerfest. Just wondering if anyone else has tried it?

I might give it a go next week and see if it works. Worst that can happen is that I flood the engine, which isn't a biggie.

Give me a shout if your interested if it works.

Cheers

[Antallica 15]

Will try it in the morning, assuming I have one of those tranny's?

[kerrynzl 3]

You can't flood the engine if it isn't going [ It has injectors not carbs ]

[wild_weston 0]

Even better then if I can't even flood it. Will try it for sure.

Cheers

[Antallica 15]

That'd be great if it's just a 'software' problem but we'll see shortly.

*Update* Think I got it (heard an obvious noise), we'll see I guess.

Edited April 6, 2008 by Antallica

[wild_weston 0]

Great that you heard the noise.

Let me know if it changes the jump. Hopefully it does and I reckon there are a lot of people out there with the same issue.

[Antallica 15]

Great that you heard the noise.

Let me know if it changes the jump. Hopefully it does and I reckon there are a lot of people out there with the same issue.

Didn't appear to change the jump this morning however I'll try doing it again. I'm not even sure I have the hardware in question though, but I do recall one of my mates asking the question why the E36 gearbox was so sh*t from 1st-2nd so I might have one.

[Yuen 16]

Do you have the link to the Bimmerfest thread? This is interesting. My E36 had a pretty bad jerk, but I no longer have it so can't try this out. From memory the BMW TIS said this was a software issue and needed a reflash of the computer, or something similar. But you know what... pretty much all the E36s with the JATCO suffer from this, so I doubt it's due to the computer 'learning' the previous owner's habits. A guy on the board has gotten it flashed by a transmission shop, and I think that fixed it... other than that, you see ads by people selling their E36 saying 'we've just overhauled the transmission' which I'm guessing is their fix for this problem.

On the topic of 'learning', after fellow member 'lidistick' and I disconnected his battery to work on his steering wheel (with airbag), and connected it back about an hour later, he reported that the transmission computer had somehow reset and now shifted much better.

I'm surprised the E46 still suffers from this problem - would have thought they'd sorted it out by then... maybe the cause for the E46 is actually different to the E36, but the symptoms are the same? Let us know how you go with the reset.

[Antallica 15]

Seemed to be running like a dream today but I could have deluded myself to think that she's better.

The mind is a wonderful thing.

[Mark 178]

I have a Jatco box and tried the method Yuen suggested which was to disconnect then reconnect the battery. It didn't work.... still have a jerky 1st to 2nd change.

I'll try the accelerator trick tonight to see if it works. I've never heard of it before in all my research into this topic.... but I do know you can check for fault codes on OBD1 cars using a similar method, so perhaps it is true!

[*Glenn* 854]

I've never heard of this either.

If the vehicle has adaptive values, you can clear the adaptions (scan tool required) and then recheck driveability. If that doesnt cure it , its a valve body mod which sometimes works, or a trans rebuild.

Edited April 8, 2008 by botanymotorworx

[Grant 4]

I was told some time ago (when I first bought the 323i) by Trevor at the BM Workshop that you can't fix it, short of a transmission rebuild. However the transmission will keep going for ages after it first appears, he basically told me not to worry about it and just ensure the trans is serviced regularly.

Cheers

Grant

[martyyn 2]

I think this one is a bit of an old wives tale.

From what Ive been told (I have a 528 touring that apparantly has the Jatco Jerk - I didnt notice anything to start with and it doesnt happen everytime) the problem is that whilst the car sits in the great Japanese car park (aka downtown) the fluid in the gearbox heats up too much which in turn strips the lining from the interior walls.

This then gets to float around with the fluid and causes the jerkiness.

One solution is to rebuild the tranny. The other is to flush it with new fluid (a cost of about 800 at the dealers as the oil is 600 alone), replace the filter and see what comes out. If its full of bits, you drive it for a while and flush it again (with another new filter) to see if its all come out.

So thats two flushes at approximately 1600 vs a gearbox rebuild at about 2500.

Thats how the dealer explained it to me anyway.

[Mark 178]

I think this one is a bit of an old wives tale.

From what Ive been told (I have a 528 touring that apparantly has the Jatco Jerk - I didnt notice anything to start with and it doesnt happen everytime) the problem is that whilst the car sits in the great Japanese car park (aka downtown) the fluid in the gearbox heats up too much which in turn strips the lining from the interior walls.

This then gets to float around with the fluid and causes the jerkiness.

Then why would it only happen from 1st to second? Surely if bits are floating around in there, all the gear changes would suffer?

[greenday-rulz21 4]

Thats interesting Martyn.

When I was looking at an E36 328i which had the Jatco jerk, I sent it in to Jerry Clayton to get their opinion. And they said don't touch it. They said that the only way to fully fix the jerk is a gearbox rebuild (at about 3k).

Drove another which had had the gearbox rebuilt and it ran flawlessly, with a receipt for just over 3k.

[Mark 178]

So a rebuild is 3k.... what about replacing the box with a 2nd hand non-Jatco unit? How much would that sting you?

[Antallica 15]

I'm thinking for the price I'd rather manual vert it.

[Young Thrash Driver 1020]

Antallica has a point

Manual conversion could cost less than 3k, depending how much the box etc is you manage to get your hands on

[wild_weston 0]

Do you have the link to the Bimmerfest thread? This is interesting. My E36 had a pretty bad jerk, but I no longer have it so can't try this out. From memory the BMW TIS said this was a software issue and needed a reflash of the computer, or something similar. But you know what... pretty much all the E36s with the JATCO suffer from this, so I doubt it's due to the computer 'learning' the previous owner's habits. A guy on the board has gotten it flashed by a transmission shop, and I think that fixed it... other than that, you see ads by people selling their E36 saying 'we've just overhauled the transmission' which I'm guessing is their fix for this problem.

On the topic of 'learning', after fellow member 'lidistick' and I disconnected his battery to work on his steering wheel (with airbag), and connected it back about an hour later, he reported that the transmission computer had somehow reset and now shifted much better.

I'm surprised the E46 still suffers from this problem - would have thought they'd sorted it out by then... maybe the cause for the E46 is actually different to the E36, but the symptoms are the same? Let us know how you go with the reset.

I was trying this on my E36. The E46 is fine, talked to a chap at Jeff Gray BMW the other day and he reckons that the E46 continuily adapts (like it says in the owenrs handbook) to your driving style. It seems pretty fine to me but apparantly will adapt more to my style of driving over time. Don't think this is the same for the E36 though.

Tried on the E36 but didn't even hear the sound after 30 secs so it doesn't work for me. I will recommend the transmission CPU reset to the next owner.

Haven't got the link to the thread on bimmerfest.