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3-Series (E36) Chat relating to the BMW 3-Series from 1992-1999. Autodoodad Specific models include: BMW 316i, BMW 318i, BMW 318iS/ti, BMW 320, BMW 323, BMW 320, BMW 324, BMW 325, BMW 328.

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#1 (permalink) Old 08-03-2009, 11:43 PM
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Exclamation Hello!...and a question!

Hello All,

I have 1995 325IC at ~89 K miles. The car has both automatic and manual options. I have a problem and would like to ask your suggestions or opinions. Thanks in advance!

When I am driving in automatic mode (D), [regardless of cold or warm engine / regardless of A/C running or not /regardless of my acceleration is gentle or aggressive], sometimes, I lose power (i.e., the RPM suddenly goes down from 2000 to 1000 for 2 seconds) and I feel a rocking (or, back and forth) movement and I can actually hear cranking from the transmission as if it is trying to engage to a lower or higher gear. Then RPM picks up, if I keep my foot on gas pedal and the gear change is back to normal. If I need to stop at a sign or at the lights, I get the same inconsistent RPM when the engine is running idle (RPM suddenly goes up to 1000 several times -whereas it should be around 500) and the transmission makes that cranking sound.

When I am driving in manual mode however, everything seems to be perfect.

I took the car to three different services, two of them are certified BMW service centers. The diagnostic computers did not pick up any codes, my transmission lamp is not lit and the trip computer's check mode comes clean every time I run systems check. I know it works because it recently gave a warning about the coolant level and it was accurate!

One of the mechanics suggested that the chip, which is controlling the timing of the automatic transmission (?), may be faulty since the problem is intermittent and occurs only in the automatic mode.

I will appreciate your insights!

Cheers,
barikan
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#2 (permalink) Old 08-04-2009, 12:22 AM
OMFG another one!?
 
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A transmission fluid change may be needed, ASAP.

BMW

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#3 (permalink) Old 08-04-2009, 12:25 AM
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Thanx

Thank you! Do you think the fluid has gone bad and causing slippage?!

EDIT: I checked the records of the previous owner; the trans fluid (along with the filter) was changed at 81.400 miles, exactly 8K miles ago. I am sorry, I have no idea, does it mean it is about time?

barikan

Last edited by barikan; 08-04-2009 at 12:37 AM. Reason: additional info!
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#4 (permalink) Old 08-04-2009, 11:35 AM
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I'm not entirely sure that this is a problem in regards to transmission fluid, particularly now that you say it was changed 8K miles ago and this is only something that happens in automatic and not manual mode.

This could be a computer related problem as your mechanic suggested and I especially believe that because you say it only occurs in true automatic mode. I'll see if I can find additional information on this.
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#5 (permalink) Old 08-04-2009, 11:46 AM
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Based on what I found at real OEM I see that your transmission is a BMW/GM 4 speed. Correct me if I'm wrong because I'm not entirely sure on this.

I used realOEM to look up this information. Click Here to view
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#6 (permalink) Old 08-04-2009, 12:03 PM
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Up-date

Hi and thanx for your help. I just got back from the service; they flushed and changed the transmission fluid but the problem persists.

I could not convince the mechanic to check ICV or MAF; from what I have been reading here, people with similar problems found solution when they are cleaned.

I still think that it is a chip-related issue for the exact reasons you mentioned; the problem is not there when I am controlling the gears. But why do I not get an error code when it is hooked up? This is frustrating.

I looked at the link you put on your reply. I am not really into cars, so it is difficult for me to tell, but my car is not 325 is, it is 325i Convertible (I only have 1st-2nd-3rd gears on manual and -D-) -I am not sure if it will make any difference.


Also, when I was talking to the main BMW service here, I was told that the BMW code for the type of transmission I had was THMR-1.

I will appreciate any suggestions.
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#7 (permalink) Old 08-04-2009, 12:13 PM
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The transmission should be the same regardless of the model and based on the fact your manual has 1,2,3 gears in manual is telling me that you have a 4 speed automatic.

It is definitely a GM transmission and the BMW service code definitely helps me verify that on this document on Google Docs

The ICV should not have an effect on the way a transmission shifts. If your engine was idling erratically at stop lights I would definitely recommend cleaning the ICV for sure but I think this problem goes beyond that. If your MAF was faulty you would also have eengine problems as well.

You could always have the transmission software updated or reloaded.

This problem also doesn't indicate that an error or transmission light would be triggered because it doesn't seem to be an actual problem with the transmission itself. I'm still trying to find some info on this to see if someone else has had the same problem.
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#8 (permalink) Old 08-04-2009, 12:21 PM
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Hi Bimmer E39,

So, please correct me if I am wrong; you are thinking that the transmission is mechanically (i.e., the hard parts) OK [because the manual is functioning] but the controlling unit (i.e., the chip or whatever it is called) may be faulty/going bad.

I discussed re-programming the chip yesterday and I was told that for the chips I had re-programming was not an option but replacement was. May be it is the next step!
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#9 (permalink) Old 08-04-2009, 12:31 PM
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Yes, I believe the mechanical parts of the transmission are in working order based on the fact that manual mode works correctly and automatic mode seems to be an issue. If both modes had a problem I would definitely be look at the mechanics of the transmission itself.

I'm not entirely familiar with the electronic system of the E36 itself, but yes, the module might have to be replaced. I know on my car the actual transmission control unit can be reprogrammed/updated so that's why I suggested it.

You could always opt to have the transmission inspected first before replacing the control module itself. Lets see if someone else has an opinion on this.
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#10 (permalink) Old 08-04-2009, 12:34 PM
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Fantastic! Thank you for your time.
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#11 (permalink) Old 08-04-2009, 12:36 PM
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No problem and best of luck!
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#12 (permalink) Old 08-05-2009, 10:57 PM
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Up-date on the problem

Hi,

Finally, I had the existing chip replaced at the mechanic today. It seems that the one on the car did not have BMW emblem and probably was an after-market Asian (Singapore) product. The new chip is made in Germany by BMW.

Although the transmission shifts smoother (and definitely the intervals are different) and there is some improvement in the gas consumption (or the trip computer's estimations are more accurate), the transmission issue (i.e., slippage in low gears during acceleration) is still there.

Manual is still functioning properly.

Now, it seems to me that the problem is either related to the transmission (i.e., the hard parts) or the high gear discs are somehow already damaged and causing slippage.

I still cannot understand why I am losing torque (RPM suddenly drops and picks up) when the slippage occurs.

I will appreciate any comments/suggestions.
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#13 (permalink) Old 08-05-2009, 11:30 PM
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Wow...I'm really shocked in all honesty. I'm also dissapointed for you as well. Your problem definitely seemed like a program issue with the transmission but it seems odd that the unit you pulled out was not a BMW spec unit...

In all honesty, I am at a loss for real answers at the moment. I'll ask my friend tomorrow what he thinks about your problem. He's an ASE Master Certified Technician so at this point I'm thinking he would be able to give me some better ideas about possible reasons for your tranny problems.
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#14 (permalink) Old 08-05-2009, 11:37 PM
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Hi Bimmer E39,

I was shocked too. I am really curious what it will come to at this point. I just feel fortunate to have some kind of service coverage on the car.

I really appreciate your efforts and I am looking forward to hearing from you.

One strange thing; when I am driving in manual mode, I treat D as the 4th gear. May be I am wrong but the car should have at least 4 forward gears. But in D, there is no further acceleration, it is not any different than 3. It does not seem right to me!
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#15 (permalink) Old 08-05-2009, 11:41 PM
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Quote:
Originally Posted by barikan View Post
One strange thing; when I am driving in manual mode, I treat D as the 4th gear. May be I am wrong but the car should have at least 4 forward gears. But in D, there is no further acceleration, it is not any different than 3. It does not seem right to me!
Hmmm, I'm not too familiar with the transmission in your car but my guess is that D is the 4th gear and it probably acts like an over drive. I am like 99.9% sure your automatic is a 4 speed.
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