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Old 05-03-2017, 03:34 PM   #1
darkgoob
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GM5 tranny issue

Car is a 2004 325ci, made in Mar. 2004.

NOTE: I called it the "GM5 tranny" because it's made by GM and the part # is 5L40-E. However I'm aware there is also something called "GM5" which is the "general module 5" that controls many functions of the car, and which is also a part found on the e46. So for the sake of disambiguation, I'm talking about the transmission, not necessarily the control module (although, for all I know, it might be involved too).

Given the following misbehavior of the automatic transmission, I mainly want to know if it's likely harmful to the car to keep driving it until I have more work done (which I intend to do within 30 days).

Any other feedback related to this issue is appreciated.

Transmission Problems

(1) In the mornings, when I would try to go from being stopped on the steep hill, the car will not want to go. Temperature could be 35-55 F, it does not seem to matter. Some mornings it will be fine; other mornings it will not want to get going on that hill, and I will have to rev it pretty good (up to 4000-5000 RPM) to start moving barely.

UPDATE: Today it engaged into gear and seemed fine going up the first hill. Then, I was at a stop light, and when I went to accelerate, it's just spinning. I shift to park and then drive again, and did not feel it engage at all when shifting. Then went to accelerate and again, no power until RPMs were upwards of 4000. The outdoor temperature is very warm today, above 85 F, but the engine temp guage was still in the blue area at this point.

(2) Whilst driving down the road after cresting that hill, around 35-40 MPH, around when the car shifts up 2 -> 3 or 3 -> 4, the RPMs will seem to flutter for a moment, like 1500-2000 or 2000-2500 back and forth oscillating, until I step on the gas or brake, at which point, it returns to normal behavior.

(3) The problem has seemed to get worse and more persistent over time. At first when it started happening, it was not so noticeable. Over the following six months it began to progress to where, sometimes I can barely get the car to move.

(4) After the car warms up, it seems fine. I can tell if the problem is going to happen by shifting from P to R to D whilst at a complete stop. If the problem is going to happen, then I won't feel anything when going into gear in those settings. However if the car has warmed up sufficiently (temp. needle out of the blue area), then when I shift into R or D with the brake depressed, I can feel the car lurch slightly as the gear engages.

(5) Tricks like putting it in Sport mode or manually selecting a gear do not seem helpful to resolve this.

Research

(1) I googled it, and found various threads here and elsewhere in which people complain of this problem. It seems there have been two TSBs and an NHTSA investigation (see this link).

(2) I found a number of sites specifically about this tranny, which is made by GM and has the model number 5L40-E;here is a great example of such a site, and the first problem it lists is exactly what I am experiencing.

(3) The second TSB is the only one I could find. It does not seem to include the vehicles manufactured after 2003, such as mine, even though my car has the same transmission. It does indicate reprogramming the transmission controller as a solution, but last time I had my car at the dealership, I asked them to ensure it had the latest firmware and they assured me it did.

Actions Taken So Far

(1) Following the advice mentioned in the forums and the NHTSA report, if I allow the car to warm up for awhile, particularly if I drive it for a short time at low RPMs on a flat road, then it seems to start functioning OK. However I am afraid of doing further damage to the transmission.

(2) I had my AT fluid replaced (which should not have been necessary after just a few thousand miles), but this did not seem to help. The mechanic told me there were no metal filings in the pan, and the fluid (which had been changed just a year before that, along with a drive shaft replacement) looked perfectly fine.

(3) I noticed the ATF container under the hood had lots of residue. However I was able to tighten it about half a turn. If that cap's seal is bad, and has a slow pressure leak, could that have been enough to cause this issue? Should I replace it? I've read this is a common issue and some say it's by design, but since the transmission issues seem equally common, perhaps they're related? (But what do I know.)

Questions

(1) Is it likely safe to keep driving or do I risk damage to other parts or to the transmission itself?

(2) Other than what I have already done, and other than having the transmission replaced/rebuilt, are there any other possible causes of this issue to investigate, or minor remedial actions to try?

(3) Is there anything that is known to cause this issue to get worse? I ask this because whether or not I opt to replace it, I would like to know if there is some way of driving the car that can make this worse, or any other types of issues that could affect the transmission controller (like electrical stuff--I did have to replace the cigarette lighter fuse recently; or loose hoses/caps).

Last edited by darkgoob; 05-03-2017 at 05:15 PM.
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Old 05-03-2017, 03:47 PM   #2
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Is your mechanic familiar with the correct filling procedure?
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Old 05-03-2017, 03:47 PM   #3
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How many miles?
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Old 05-03-2017, 04:01 PM   #4
darkgoob
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Quote:
Originally Posted by WDE46 View Post
Is your mechanic familiar with the correct filling procedure?
Yes. I take it to a BMW shop.
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Old 05-03-2017, 04:03 PM   #5
darkgoob
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How many miles?
118K, appx.
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Old 05-03-2017, 05:09 PM   #6
darkgoob
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I just updated the main post in the "Transmission Problems" section, part (1). The issue seems a bit more complex than I first described.

Last edited by darkgoob; 05-03-2017 at 05:09 PM.
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Old 05-03-2017, 05:11 PM   #7
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That ATF fluid reservoir under the hood is for your power steering system.
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Old 05-03-2017, 05:13 PM   #8
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An issue only on a hill could be based on a low fluid level.

Does the issue happen when driving on level roads?
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Old 05-04-2017, 02:39 PM   #9
darkgoob
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Quote:
Originally Posted by SSchwab View Post
An issue only on a hill could be based on a low fluid level.

Does the issue happen when driving on level roads?
Yes, it happens on level roads also. I think it is exacerbated by being on a hill because the vehicle takes more power to get moving due to the incline. But I have also experienced this on a level part of the road.

Mind you, the issue clears up after I have been driving for awhile and the transmission has had time to warm up. This seems consistent with the issue description provided in the TSB, which says the cause is "insufficient pressure boost for the C1 forward clutch" after a cold start.

Once the car warms up, the fluid or the housing itself presumably expands, increasing the pressure or stopping the leak, and resolving the issue temporarily (until the next cold start)--hence why NTHSA report indicates BMW told them the issue is "self-correcting" and drivers would adapt to it.
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Old 05-04-2017, 03:51 PM   #10
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Are you able to do your own work? Can you do your own ATF/filter replacement?
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Old 05-05-2017, 08:01 AM   #11
Alfa Andy
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Darkgoob-
#1 Do your best to not drive the car whilst the transmission is slipping (engine revving but car not moving as it should). This will cause expensive damage to the transmission.
#2 Look in your owners manual and learn about the fluid reservoirs under the hood.
#3 Better yet, purchase a Bentley repair manual. It is chock full of great information about how to maintain and repair your BMW.
#4 If the power steering fluid reservoir cap is seeping, replace the o'ring seal on the cap. I will post the part number at another time.
#5 Search for my thread '330xi autotrans slipping' in this forum.
#6 I have found the solenoids that I replaced on Amazon for more reasonable prices. I will post this information on my thread later today.
#7 Follow my fluid adding procedure. I have had to top-up the fluid on many cars serviced elsewhere.
Please post the resolution of your problem.
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Old 12-14-2017, 06:49 AM   #12
darkgoob
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Quote:
Originally Posted by Alfa Andy View Post
Darkgoob-
#1 Do your best to not drive the car whilst the transmission is slipping (engine revving but car not moving as it should). This will cause expensive damage to the transmission.
#2 Look in your owners manual and learn about the fluid reservoirs under the hood.
#3 Better yet, purchase a Bentley repair manual. It is chock full of great information about how to maintain and repair your BMW.
#4 If the power steering fluid reservoir cap is seeping, replace the o'ring seal on the cap. I will post the part number at another time.
#5 Search for my thread '330xi autotrans slipping' in this forum.
#6 I have found the solenoids that I replaced on Amazon for more reasonable prices. I will post this information on my thread later today.
#7 Follow my fluid adding procedure. I have had to top-up the fluid on many cars serviced elsewhere.
Please post the resolution of your problem.
Turned out, it was the transmission fluid filter.

First mechanic replaced my fluid twice and I would have assumed this filter also, but nooo. Took it to a transmission specialist and he goes, “Let me guess, they didn’t check or replace the filter? Nope. This filter was so shot it literally just fell out. The o-rings were just gone.”

LOL.

New transmission fluid filter and fluid, then boom it is driving like BRAND NEW. I feel like 100HP extra just got added to my car as well. Suddenly I have a BMW again.

And it only cost $250!!!
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Old 12-14-2017, 07:35 AM   #13
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Quote:
Originally Posted by darkgoob View Post
Turned out, it was the transmission fluid filter.

First mechanic replaced my fluid twice and I would have assumed this filter also, but nooo. Took it to a transmission specialist and he goes, “Let me guess, they didn’t check or replace the filter? Nope. This filter was so shot it literally just fell out. The o-rings were just gone.”

LOL.

New transmission fluid filter and fluid, then boom it is driving like BRAND NEW. I feel like 100HP extra just got added to my car as well. Suddenly I have a BMW again.

And it only cost $250!!!
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Old 12-14-2017, 11:36 AM   #14
darkgoob
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Shout out to Scott at River City Transmission in Portland. This guy is really great.
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Old 12-14-2017, 07:58 PM   #15
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Great to hear such a simple fix !

I am glad they were able to look at it and find the problem for you.

Last edited by Captain_BMW; 12-14-2017 at 07:59 PM.
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2004 325ci, cold start issue, gm5 issues, transmission

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