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'04 325Ci, 136K miles. GM auto. New to me.

I do not have much of a service history on it, but given its condition, I would guess that it's been well treated. Car is near flawless, drives and shifts beautifully.

I do have an intermittent cog of death. Generally no COD on a cold start, but pretty frequent when warm. I never get it during a drive. It is either there at start up or not. When it is present, the shifts seem a little more abrupt, but it is not in limp mode. It revs just fine.

The first garage I brought it to, as supposedly reputable BMW specialist says bad EGS control unit. Need new, can't go with used. 1400 installed.

When I posted that here and at bimmerforums, everyone said run away. It likely isn't the problem and if it is, you can slap a used on in there and be fine.

So, yesterday I stop by my local garage who I trust, but figured I needed to take the bimmer to a "specialist". Come to find out one of the techs there has 6 years experience at a BMW dealership. So, he is comfortable with BMWs.

I told him I was going to do the trans fluid/filter change.

His recommendation- Don't even think about dropping the pan. You're opening a can of worms. Screen doesn't get clogged anyway and getting the pan back on without leaks is a major PITA. He said drain enough to inspect it. If it looks good, go ahead and do a drain/refill. If it looks bad, top it off and keep your fingers crossed. He said he has had numerous experiences with neglected trannies grenading within 500 miles of a fluid swap.

I have heard this same story from numerous sources.

My question is how do I know when it is too bad to change?

What do you think about skipping the filter change?
 

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Here to serve y’all
2004 330Ci 85k miles
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11,097 Posts
It is sad there is so much misinformation, fear, uncertainty, and doubt being spread out there.
Yes, change the ATF, filter, pan gasket.

Read post #1 in this thread.

I would also update the EGS software to the latest.
 

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I bought mine with 121k miles and the original fluid.

I dropped the pan did fluid and filter. Two weeks later I did a drain and fill. I’ve been doing scheduled fluid and filter changes at 50k mile intervals. Valvoline Dex 6 full synthetic.

I am now at 234k miles and it operates as good or better than the day I got it.

I think the bad stories are from people that neglect the trans and do a fluid and filter change as a reaction to the trans having some sort of problem.


Sent from my iPhone using E46Fanatics
 

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Bough my car at 90K, changed my transmission fluid and filter at 95 K and 145K, still working fine.
 

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2003 330cic, 2003 325iT
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'04 325Ci, 136K miles. GM auto. New to me.

I do not have much of a service history on it, but given its condition, I would guess that it's been well treated. Car is near flawless, drives and shifts beautifully.

I do have an intermittent cog of death. Generally no COD on a cold start, but pretty frequent when warm. I never get it during a drive. It is either there at start up or not. When it is present, the shifts seem a little more abrupt, but it is not in limp mode. It revs just fine.

The first garage I brought it to, as supposedly reputable BMW specialist says bad EGS control unit. Need new, can't go with used. 1400 installed.

When I posted that here and at bimmerforums, everyone said run away. It likely isn't the problem and if it is, you can slap a used on in there and be fine.

So, yesterday I stop by my local garage who I trust, but figured I needed to take the bimmer to a "specialist". Come to find out one of the techs there has 6 years experience at a BMW dealership. So, he is comfortable with BMWs.

I told him I was going to do the trans fluid/filter change.

His recommendation- Don't even think about dropping the pan. You're opening a can of worms. Screen doesn't get clogged anyway and getting the pan back on without leaks is a major PITA. He said drain enough to inspect it. If it looks good, go ahead and do a drain/refill. If it looks bad, top it off and keep your fingers crossed. He said he has had numerous experiences with neglected trannies grenading within 500 miles of a fluid swap.

I have heard this same story from numerous sources.

My question is how do I know when it is too bad to change?

What do you think about skipping the filter change?
I have completely flushed it in autos at 125k, 150k, and 190k. All went fine. All of them needed it. All shifted better after.

ignore the guy at the shop
 

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Changing tranny fluid doesn't cause damage. People tend to change it as a result of a problem that's already presented itself then complain that the problem got worse or wasn't resolved. If you suspect changing your fluid will kill your tranny, then I suspect your tranny is probably very close to being dead already.
 

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the consensus i've heard over the 10ish years i've been an active participant in the bmw community (and have been working on bmws for that long) is that you're much better off doing a fluid drain rather than a full flush.
 

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2004 325i automagic
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OP, if you are unsure then go slow and do a drain and fill like the second tech advised. That will get about 4.5 quarts of new ATF in there out of a total of 9.5 quart capacity and will be a more incremental approach versus an all out flush or doing nothing and letting problem get worse. Drive it for a week, then do another drain and fill. A third drain and fill will get you close to 85% to 90% new ATF in there.

I did the triple drain and fill with my 2004 325i gm transmission at about 115k miles not long after buying it used, except I dropped the pan and changed the filter on the first change (6 to 6.5 quarts new fluid). It also had a leaking selector shaft seal that was causing sluggishness and bad mpg, but fixing the leak and getting fresh fluid in it pretty much restored it. Since then I have done a drain and fill every 20k miles or so because again one d/f is a little less than half a fluid change; were I doing a complete fluid change I could go longer between changes. I now have 172k miles on it and it still shifts great (as long as I keep up with the fluid changes).

You may also want to check for leaks. The selector shaft seal is a common leak, but the original pan gasket can also leak. I think sealing problems happen if someone in a hurry pries off the old pan with a screwdriver and mars/dents the sealing surfaces. It might also take some time to clean off the old gasket without damaging things and that may be another reason why the second tech doesn't want to touch the pan/fliter.

Like others have said, a fluid change is only a problem on an already failing transmission, where all the grit and metal particles in the old fluid is what is providing enough friction for the gear clutches to engage/grab when pressed together. That is why the second tech said to check condition of the old fluid ... if you see grit and metal bits in the old fluid then you want to keep the old flulid in there because that is what is keeping it working.

Btw, the "flush" people here are referring to is NOT a power flush with any kind of cleaning solvent (bad) that the warnings are typically about. It is just disconnecting the output line that plugs into the atf cooler behind the radiator and pointing it into a big bucket, running the engine to have the transmission pump out fluid while adding fresh fluid at the fill hole untill you see fresh fluid exiting into the bucket. (Turning engine off as needed if what you can pump in is less than the outflow.) This could also be described as just changing all the fluid at once instead of the proverbial "flush".
 

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His recommendation- Don't even think about dropping the pan. You're opening a can of worms. Screen doesn't get clogged anyway and getting the pan back on without leaks is a major PITA. He said drain enough to inspect it. If it looks good, go ahead and do a drain/refill. If it looks bad, top it off and keep your fingers crossed. He said he has had numerous experiences with neglected trannies grenading within 500 miles of a fluid swap.
That's a new one. 😄

A transmission that fails after a service is one that was on its way out anyway.

I would be wary if there was limited data. That is not the case with this platform, however, as many of us have completed numerous transmission services on E46s without a single issue and with very noticeable improvements every time. In most cases, the first service these transmissions saw was after 100K+ miles on the original fluid.

That said, please double check a) the health of your battery and b) that your negative cable is securely fastened to both the battery and its body mounting point in the trunk. Dealt with an intermittment cog warning on a former E46 and the root cause was electrical (TCU not getting the voltage it needed).

Long shot, but worth ruling out IMHO.
 

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OP, if you are unsure then go slow and do a drain and fill like the second tech advised. That will get about 4.5 quarts of new ATF in there out of a total of 9.5 quart capacity and will be a more incremental approach versus an all out flush or doing nothing and letting problem get worse. Drive it for a week, then do another drain and fill. A third drain and fill will get you close to 85% to 90% new ATF in there.

I did the triple drain and fill with my 2004 325i gm transmission at about 115k miles not long after buying it used, except I dropped the pan and changed the filter on the first change (6 to 6.5 quarts new fluid). It also had a leaking selector shaft seal that was causing sluggishness and bad mpg, but fixing the leak and getting fresh fluid in it pretty much restored it. Since then I have done a drain and fill every 20k miles or so because again one d/f is a little less than half a fluid change; were I doing a complete fluid change I could go longer between changes. I now have 172k miles on it and it still shifts great (as long as I keep up with the fluid changes).

You may also want to check for leaks. The selector shaft seal is a common leak, but the original pan gasket can also leak. I think sealing problems happen if someone in a hurry pries off the old pan with a screwdriver and mars/dents the sealing surfaces. It might also take some time to clean off the old gasket without damaging things and that may be another reason why the second tech doesn't want to touch the pan/fliter.

Like others have said, a fluid change is only a problem on an already failing transmission, where all the grit and metal particles in the old fluid is what is providing enough friction for the gear clutches to engage/grab when pressed together. That is why the second tech said to check condition of the old fluid ... if you see grit and metal bits in the old fluid then you want to keep the old flulid in there because that is what is keeping it working.

Btw, the "flush" people here are referring to is NOT a power flush with any kind of cleaning solvent (bad) that the warnings are typically about. It is just disconnecting the output line that plugs into the atf cooler behind the radiator and pointing it into a big bucket, running the engine to have the transmission pump out fluid while adding fresh fluid at the fill hole untill you see fresh fluid exiting into the bucket. (Turning engine off as needed if what you can pump in is less than the outflow.) This could also be described as just changing all the fluid at once instead of the proverbial "flush".
^This.

OP, I don’t personally drive AT’s anymore (excluding my wife’s) but this advice pretty much covers my understanding— and put very well.
 

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Changing ATF fluid won't fix incorrect work of transmission. If gearbox is fine, then you might notice minor changes, like softer gear switching. ATF fluid change probably prolongs life of transmission, but it won't stop disks wearing, so eventually transmission comes to be rebuilt. Unlike engine oil, which not only lubricates but also wash engine and therefore has to be changed regularly, there are no products of burning in gearbox, so ATF has very basic washing features. It become black because of fine particles of friction discs wearing and it doesn't really affect performance of transmission. You can change it as often as you wish, but you have to follow procedure of filling it with fresh ATF - and I can't stress enough how it is important to make sure you fill it in right temperature - get gearbox fluid temp hotter than 40C while filling with fluid and you will have your transmission underfiilled.
 

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Changing ATF fluid won't fix incorrect work of transmission. If gearbox is fine, then you might notice minor changes, like softer gear switching. ATF fluid change probably prolongs life of transmission, but it won't stop disks wearing, so eventually transmission comes to be rebuilt. Unlike engine oil, which not only lubricates but also wash engine and therefore has to be changed regularly, there are no products of burning in gearbox, so ATF has very basic washing features. It become black because of fine particles of friction discs wearing and it doesn't really affect performance of transmission. You can change it as often as you wish, but you have to follow procedure of filling it with fresh ATF - and I can't stress enough how it is important to make sure you fill it in right temperature - get gearbox fluid temp hotter than 40C while filling with fluid and you will have your transmission underfiilled.
It's not the "basic washing" that challenges ATF, but rather the heat generated in the torque converter. Especially in older transmissions like these where the torque converter is allowed to slip, as a torque multiplier to compensate for the lack of in-between ratios.
 

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Agree with most of the above. Bear in mind he has a warning light and that needs to be looked at.

Hoping for a service/fix scenario is unwise.

Id scan, diagnose and maybe change 4 qts at a time, predicted upon the results of the scan.
 

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2003 330cic, 2003 325iT
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Changing ATF fluid won't fix incorrect work of transmission. If gearbox is fine, then you might notice minor changes, like softer gear switching. ATF fluid change probably prolongs life of transmission, but it won't stop disks wearing, so eventually transmission comes to be rebuilt. Unlike engine oil, which not only lubricates but also wash engine and therefore has to be changed regularly, there are no products of burning in gearbox, so ATF has very basic washing features. It become black because of fine particles of friction discs wearing and it doesn't really affect performance of transmission. You can change it as often as you wish, but you have to follow procedure of filling it with fresh ATF - and I can't stress enough how it is important to make sure you fill it in right temperature - get gearbox fluid temp hotter than 40C while filling with fluid and you will have your transmission underfiilled.
Are you positive (I am not)?

My understanding is that the dark color of transmission fluid was due to heat-caused oxidation, not just murkiness. Oxidation definitely affects performance. The heat is not from direct combustion, but it still can be quite high.

And 150-200k miles is definitely outside the operating limits of transmission fluid.
 

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2004 325i automagic
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It's not the "basic washing" that challenges ATF, but rather the heat generated in the torque converter. Especially in older transmissions like these where the torque converter is allowed to slip, as a torque multiplier to compensate for the lack of in-between ratios.
I think there is something to the heat degrading atf over time. Over last couple years, I have noticed a need to change ATF fluid (due to reduced shift performance) in the early fall after a summer of 90F to 100F temps with lots of stop and go drivng as well as long road trips in the summer heat going up and down mountains. Plus I am in a hilly area which I think adds to the transmission temperature load. I put alot of miles on the car in general, so it sees a lot of run time as well on a weekly basis.

Just a correlation I've noticed and that putting new fluid in (even if only 4 or 4.5 quarts) seems to noticeably restore shift performance. No doubt this just delays the inevitable in terms of wear, but I'd rather have the better performance in the meantime before it finally does crap out (at 172k miles now). I'm running Valvoline Max-Life in the red bottle, fwiw.
 

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Agree with most of the above. Bear in mind he has a warning light and that needs to be looked at.

Hoping for a service/fix scenario is unwise.


Id scan, diagnose and maybe change 4 qts at a time, predicted upon the results of the scan.
Good point ... since it already is symptomatic with the COD showing itself, there may be error codes (either in the dme or the egs) that are worth looking at.

Wannabemer,
The software that BaliDawg mentions in post #2 that he uses to update the transmission computer will also read all the codes in both the engine computer (dme) and transmission computer (egs), and all other control units on the car for that matter. All you need is a windows laptop and a $20 to $30 k+dcan cable off of amazon or ebay. Its a worthwhile investment in a little time and a $30 cable to have that software to help in troubleshooting these cars.
 
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