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      06-11-2019, 09:11 AM   #1
taillights
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SMG transmission advice

I have been looking at a one owner 2003 z4, 3.0 with 86,000 miles. I am nervous about the SMG. Any advice?
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      06-14-2019, 06:29 PM   #2
rjahl
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Quote:
Originally Posted by taillights View Post
I have been looking at a one owner 2003 z4, 3.0 with 86,000 miles. I am nervous about the SMG. Any advice?
I have not read anything good about that gearbox. It's pretty rare,
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      Yesterday, 11:41 AM   #3
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I had a 2004 E46 330i ZHP with the SMG gearbox. I will say that while there is not much good written about it I enjoyed it very much, and the more I drove it (mostly in manual mode as it was a 3rd car for summer weekend drives) the more I liked it. That being said I was very gentle with it and there is an intuitiveness and feel to driving it so that it operates as well as it should.

Now at the same time I lived in constant fear because everything written about the SMG and SMG II transmission was basically it is a timed grenade that could go off at any time, high mileage, low mileage, and under a wide range varying circumstances for apparently no consistent reason. On top of all that it is not a well understood system, costs a fortune to diagnose (which is often done incorrectly) and can cost I’ve read anywhere between $10-15k to repair/replace. There are cheaper and easier fixes but that is not how the dealerships do it. There is a “Salmon Relay” which is often a culprit of poor performance or lost gears (probably $25 but the dealership diagnostic calls for replacing $1000’s of dollars of parts instead). There is also some reported problems with the hydraulic pump (maybe $5-600 fix). If you end up with gearbox problems and it is not one of those things you are probably screwed... at this point people often opt to do a 5/6 speed swap and the reported cost of this were somewhere around $3-5000. If it’s not one of the cheap, easy DIY fixes mentioned above or a fluid level adjustment your best bet is the manual swap.

I had that E46 for 5 or so years (up to maybe only 60,000km) and loved it and never had a problem with it. I never wanted to sell it and had refreshed most of it with new OEM parts and drove it like I planned to keep it forever. The only reason I ended up selling it was it wasn’t reasonable to have two summer cars. At the same time it was a weight off my mind that I didn’t have to worry about the trans grenading and causing me a bunch of stress and money.

Also worth mentioning is that it is often difficult to differentiate in researching both problems and fixes is that there is an SMG and SMGII transmission. I believe the SMGII was the more common and was what was found on the S54 E46 M3. Mine was the SMG and if I was guessing I’d say that it is also the SMG in the car you referenced.

One further note is people probably abused the M3’s and in my opinion this could probably/possibly account for the higher failure / problem rates. There was also a launch mode. I only tested it but again I wasn’t drag racing and I’m sure it wasn’t great for the trans.... lol

One final addition to be aware of is software programming for the transmission. I doubt there is much support left if the issue turns out to be a coding problem.

Sorry for the long ramble-ey post. This was from long ago and the info is from memory and came back to me in pieces...

Good luck

Last edited by ZMCoupe; Today at 07:33 PM..
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      Today, 10:04 AM   #4
taillights
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SMG transmission

ZM coupe, thanks for the lengthy comments. You have confirmed my worst fears. I will pass on this car.
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      Today, 07:34 PM   #5
ZMCoupe
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Quote:
Originally Posted by taillights View Post
ZM coupe, thanks for the lengthy comments. You have confirmed my worst fears. I will pass on this car.
For peace of mind probably for the best. Glad I could provide some info. Good luck with your search.
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