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DIY: Do It Yourself
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Old 03-23-2013, 02:31 PM   #1
antonmn
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Join Date: Apr 2009
Location: Minneapolis (Bryn Mawr)
Posts: 518
My Ride: 02 325Ci
"Soft" Torque Convertor Clutch Engagement

I'm trying to figure out if my 161,000 mile 325Ci's TCC behavior is normal or if I should be worried.

I've always been greatly annoyed at the TCC in this car. It's always locking and unlocking. It's hyper.

But what I've noticed is that when just cruising along at 65 mph is that I'm hearing fluctuations in engine RPM, and I see it on the tach. It's always up and down 50-100 revs, even with constant throttle pressure.

Should I do a fluid and filter swap? I did one when I bought the car at 133k. The filter was in rough shape and the fluid was dirty but not awful.

I haven't scanned lately, but I haven't gotten any codes. Is this just normal?
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Old 03-24-2013, 03:54 AM   #2
jjrichar
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The setup in the BMW is a little different to other makes that use the same transmission. In the BMW it doesn't totally lock, and fully unlocks much more often (when taking your foot of the gas for example). It shouldn't however being fluctuating when driving down the highway with constant throttle. It probably hasn't thrown a code as it isn't outside the tolerances yet. Only a matter of time.

Definitely a filter and oil change is the first thing to do. If this was my car, I would either do a filter and total oil flush, or do the filter, and then multiple oil changes over a short period. After 160k, the oil will be totally shot, and you want to get rid of as much of it as you can. The way clutches bind together in a wet clutch (ie. in an auto transmission) is very dependent on the oil. You will probably find the transmission drives much better as well. Regular fluid changes are without a doubt the best thing you can do to keep your transmission driving well for as long as possible.
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Old 03-26-2013, 09:34 PM   #3
antonmn
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Then I'll go pick up a filter and a few quarts tomorrow!

I had the fluid and filter changed 4 years ago when I bought the car at 133K but haven't touched it since.

I have noticed with every single other auto I've owned a simple fluid changed made a HUGE difference in shift quality. I didn't know if there was anything unique about this application because I also have an Audi A6 also with the 5hp19. It locks up hard and stays locked up. (That one has almost 200k and has had 3 services, all after 100k)
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Old 03-27-2013, 12:29 AM   #4
jjrichar
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Coincidently my wife's car is an Audi Allroad with the 5HP19. Having the diagnostic software for both cars, and able to see what the TC was doing with respect to input/output speeds, it was interesting to see that the Audi setup with the TC is completely different to the BMW. The BMW is a lot smoother to drive, but you don't feel like you have a direct connection between your right foot and the driven wheels like you do in the Audi. Our Audi was having some TC slippage issues soon after we bought it (about 120,000 km) and fluid changes every 10,000 km since has eliminated the problem.
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Old 03-27-2013, 12:06 PM   #5
05AlpnWht325
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Very good info on this particular problem
Will keep this in mind for future maintenance
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Old 03-29-2013, 12:13 AM   #6
antonmn
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I dropped the pan and filter tonight. Given that it's only been 30,000 miles since it's last service I was dismayed by what I saw: the magnets were soiled, the fluid was very dark. Whoever think these units don't need to be serviced is CRAZY! When I topped the unit off, the fluid that came out of the fill hole looked awful. I'll be doing a fluid swap again fairly soon!

I only drove the car a few miles, but it seems like the performance is a lot better. The shifts feel more solid, and the T/C seems to hold stronger. I hate to think of what all that material clinging to the magnets means for the life expectancy of the unit, but it's plainly obvious to me that the fluid can't stay in there as long as many assume.

I don't think I ever was able to get into the trans module of INPA. I'd be curious to have a closer look of what the T/C clutch is doing.
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Old 03-29-2013, 06:17 PM   #7
jjrichar
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Don't be too worried about some sludge collecting on the magnets. The natural engagement of the clutch packs (which consist of alternating friction disks and steel disks) will produce tiny ferrous particles that will then cling to the magnets. If it's just black sludge, this is a sign of a normally operating transmission. It's if you have a serious build up of clearly silver iron filing type particles, then you really need to worry. Like I said, I change the fluid on both mine and my wife's transmission every 10,000 km. There is always a slight build up of black sludge on the magnets, however the oil will still have a dirty golden look about it. When it's like this, you know that there is always good fluid in it. A lot of people may argue that this is overkill, but all I know is that the transmissions run like new.
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