Longtime BMW owner and have owned and maintained lots of them. I bought an 07 530xi with 120k. Trans has never been services as far as I can tell. I plan on doing the f/r diffs and transfer case this weekend. Bought the ZF kit from FCP Euro but now I am having second thoughts about doing the fluid/pan change due to concerns about grenading the unit.

So.... should I do the job or just let it eat? Trans has zero problems. Shifts perfectly. No silent codes stored.

 

I do them all the time after 100k. Drain and fill will not hurt it.

 

Fluid changes hurting transmissions is mainly an urban legend. It is theoretically possible that a fluid change on a tranny that's really on its last leg could cause it to hasten the demise slightly, but in general a transmission fluid change (and in the case of our ZF transmissions, a Mechatronics refresh) is the best thing you could possibly do to keep the car on the road for many more years. At 120,000 miles, it's due, and you might be surprised that the "perfect shifting" gets better. ;-)

 

Capture all the LifeGuard 6 that comes out of the ZF and measure it.

It will give you piece of mind, when we put back the same amount back in (and you have done the second fill correctly).

 

I have just done this on mine however I have purchased new square seal and mechatronics tubes as well. My car has fewer miles however trans have never been serviced so it contained 15 year old fluid. It shifts much better after the change, however I am debating on swapping mechatronic solenoids as well. Anyway it shouldn’t hurt to replace fluid with a fresh one.

 

FWIW, I always suggest not swapping out working solenoids. They're VERY simple devices (really just an electromagnet with a moving shaft). There's not much to go wrong, and most times if they're misbehaving it's because of the effect of dirty fluid. Given the fact that a working solenoid it almost certainly going to last longer than the car, and that any new solenoid has a higher likelihood of failing than the original (look up "bathtub curve") - AND the fact that the market is fairly saturated with knockoff and counterfeit parts (that will likely NOT last the lifetime of the car), I'm a huge fan of status quo.

 

I agree with your statement although not entirely. In order for the solenoid and valve body tow work as you know proper pressures have to be maintained. That requires cleanliness. With fluid not replaced for that many years it is certainly dirtier than should be. I have seen some videos showing that thin silicone film that is on the plate between two halves slightly broken therefore allowing fluid flow where it shouldn’t and that will affect transmission behavior. I am not mechanic by no means. It just makes a lot of sense. There is special equipment allowing to measure pressures in valve body etc that every specialized shop working in transmissions should have. Without it you just need to take things apart and check. Those solenoids are also seated on rubber orings. There are rubber elements inside the body that can be replaced as well that become flat from pressurizing. I’ve done some research on that matter. But I will also say don’t replace what isn’t broken. That preventative maintenance thing is being pushed by many of those online retailers selling parts and while in many instances it makes sense we have to stop at some point cause those while you in theres can become expensive quickly.

 

If there's anything I've picked up from deep diving into ZF 6HP arcana it's that the valve body is the key to a long transmission life. I've read the internals are very high quality that will last forever, but they are hamstrung by lax maintenance and idiotic "lifetime" fluid promises. Take care of it, it will take care of you. True for many things I suppose.

• Absolutely change the seals, when they go they stress the clutches, friction plates, etc., which leads to damage. ZF recommends fluid change every 60k miles.
• Consider changing solenoids while you're in there, or plan to in the next 30k. It's about $300 and any shop is going to charge way more.
• Go to https://www.thectsc.com for your solenoids and other ZF parts. You will need to get part numbers from the production stamp to get the exact parts you need.
• If you're planning for the long haul, or just want to upgrade your shifting experience, put in a Sonnax Zip kit, separator plate and rebuild the valve body. $250 and a few meticulous hours later and you've just upgraded your shifting to kick ass level.
• Put that laser thermometer away. Only the TCU knows the true temperature of the fluid, certainly not the plastic pan. Use a scanner, or INPA

 

Hey LongRoof,

With all your deep diving on ZF 6HP's, why are the bridge seals and sleeve seals wearing or cracking?

Next:

You mentioned ZF says change the LifeGuard every 60,000. Does ZF also say change the bridge seal and sleeve seals every... (place mileage here).

 

High pressures, heat, wear and tear, plus plastic and rubber cause them to leak and crack over time and miles. These show up as rough shifting, inability to get out of Park (bridge seal), hard downshifts (2-1), clunks.

I don't recall a specific mileage, but considering FCPEuro's Fluid change kit includes the the seals it's probably practicality and experience leading them to recommend you change 'em out while you're there.