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Hello:

This is my first post here - looking for insight and advice.

I have a 1997 BMW with 96K miles and a ZF 5-speed auto tranny (5HP30), which is making a rythmic droning noise upon lockup clutch engagement. Otherwise, it drives fine with no noise. The shop manual says this noise is due to a faulty torsion damper, and recommends torque converter replacement. Is this accurate? Is this my only option?

Hoping to avoid this expensive repair, can I simply disconnect the lockup solenoid? A 10% drop in fuel economy wouldn't bother me.

Thanks for any help!  

I don't really think that's a good option but you could try it. How much are you getting quoted for installing a new torque convertor?  

440t4:
I don't really think that's a good option but you could try it. How much are you getting quoted for installing a new torque convertor?

Labor $650 + parts. Initial parts quotes are not in yet, but I'm sure it will total $1200-$1400.

I mainly want to verify the source of the noise, thereby validating the necessary work. The shop I'm talking to doesn't seem to know more than I do. I get the impression these tranny shops don't really want to diagnose problems; they merely want to pull and replace parts - namely the torque converter.  

What model is it?  
Journeyman mechanic, transmission builder since 1963.

Any lights on ? Did you scan the computer for any codes?  

I would avoid disconnecting the lockup just to save a few bucks.  Unless you view the oil schematics of that transmission....you could be setting yourself up for a bigger nightmare.

Most transmissions require lockup to work to provide more lube and/or cooling to the planetaries (or other essential hard "expensive" parts).  So cutting corners there will bite you big time in the very near future.  

However, I must admit that I am not very familiar with the schematics of that particular transmission, but have yet to come across one when doing such "repair" (disconnecting lockup) has not bit me in the buttocks big time.  Just a lil heads up for ya brother.  

My BMW model is the 840Ci, now a collector car. It shares the same drivetrain with the more common 540i and 740i from 1996-1997. There are no warning lights on the dash and no fault codes are present. The problem is lockup noise and noise only. Very annoying. No shuddering. It shifts fine.

Is the "torsion damper" inside the torque converter? I assume the torsion damper is similar in function to a driveshaft flex disc ("guibo")?

It sounds like unplugging the lockup solenoid may cause problems. I'm also concerned the ensuing fault code will, in turn, cause the tranny to go into "limp home" mode. Here is a link to the control module wiring diagram (pin 32 controls the lockup solenoid):

BMW 5HP-30 control module diagram

Maybe torque converter replacement is my only option...a frightening prospect ($$)  

Sounds to me that you will just have to replace the converter.  You already know there is a bulletin that is describing your problem and the fix.  So I would replace the converter and keep that collector car in tip top shape.

This is just a recommendation, please bear in mind that I am just going by your symptoms in your post.  I say this because yes, it is expensive and "maybe" this is not the solution.......but from all that you have put out, it seems reasonable to me your problem is isolated to the torque converter.

And, I'm just being honest now, the torsion damper is a part on some converters (some don't have them), and they do fail.  I am not a converter rebuilder, but if it were my educated guess (for whatever that is worth), I would bet that is where your problem is.  

Where are you located? If you're in the Northeast i may be able to save you some money.  

Thanks for the feedback, all.

I'm located in central Texas. I will probably go with converter replacement then , but I'll have to live with the problem for the time being. Shifting into sport mode (manual shift) keeps the tranny out of lockup, and stepping on/off the throttle upon lockup causes it to drop lock. And I can always turn up the radio  .