BMW Z3 Trans Issues: Shifting Problems & Grinding Noises

Hey there! Some experience with cars here. I had a similar issue with my 1999 BMW Z4 last year. The symptoms you're describing sound exactly like what I went through, those grinding noises really got me worried! Turned out the transmission control unit was shot. Took it to my regular workshop and they diagnosed it after running some tests. The repair cost me around 1000 Euro, but it's been running smoothly since then. Before jumping to conclusions though, could you share: Current mileage? When did you first notice these symptoms? Have you had any transmission work done before? Any check engine lights? BTW, my has a Z3 too, so I know these models can be tricky with transmission issues. Let me know these details and I might be able to help further!

Hey, thanks for the detailed response! My Z3 is at 60810 KM and had its last service about two months ago. The symptoms started appearing gradually over the past few weeks. No previous transmission work done, but yeah, I've got that pesky check engine light on now. The transmission control unit issue you mentioned sounds pretty similar to what I'm experiencing. It's somewhat reassuring to hear it was fixable in your case. Did you notice any specific warning signs before the TCU completely failed? Also wondering if they had to replace the entire unit or if theyaged to repair it? Thanks for offering to help, really appreciate the insights from someone who's been through this!

Hey again! Thanks for those details about your Z3. Yeah, looking back at my experience with the TCU issue, I noticed some warning signs before it completely went south. Started with occasional hesitation when shifting from park to drive, then got worse with unusual gear slips, especially between 2nd and 3rd. The grinding noise was the last thing that showed up, maybe a week before I took it in. In my case, they had to replace the entire TCU, repair wasn't an option because several electronic components inside were fried. Your mileage is actually quite similar to what mine was when this happened (I was around 65000 KM). One thing I forgot to mention in my first reply, before changing the TCU, they checked the transmission fluid level and quality. That's always worth looking at first since it's a much cheaper fix. But given your symptoms match mine so closely (especially that grinding noise and the check engine light), I'd bet you're dealing with the same TCU issue. After the replacement, it was like having a new car, all the shifting problems disappeared completely. Just make sure you get it checked soon because driving with a failing TCU can potentially cause more damage to other transmission components. Let me know how it goes!

Thanks so much for all this detailed info! It's really helpful to hear about your experience, especially since our situations seem so similar. Those warning signs you described, the hesitation and slipping between 2nd and 3rd, that's exactly what I'm dealing with right now. You've actually made me feel a lot better about this whole situation. I was worried I might be looking at a complete transmission replacement, but a TCU issue seems more manageable. I'll definitely get it checked out this week, don't want to risk any additional damage like you mentioned. I'll make sure they check the transmission fluid first (fingers crossed it's just that!), but I'm mentally prepared for the TCU replacement if needed. The price you mentioned isn't cheap, but it's better than what I was imagining. Really appreciate you taking the time to share your experience in such detail. I'll probably update once I get it sorted out. Thanks again for all the help!