longroofe61

2008 535xi E61 205k ZF 6HP21X

Shortly after starting my E61 Turbo and Oil Pan Gasket project I jokingly said I am viewing this more as a new hobby than a week long project. This has proved too true as I enter my 3rd month without the car. Long Story short, after replacing turbos, oil cooling lines, water pump, an axle and pretty much every seal under the car, I start cautiously (<60 mph) driving the car while waiting for my alignment appointment. It was feeling good. At 120 miles or so I made a quick stop one day, returned 2 minutes later and the car was dead. Huh?, But its a brand new battery. I sort that out, start the car and the transmission won't shift out of Park for anything. Immobilized. As I rarely drive without my Foxwell NT 510 elite BMW scanner I was quickly on the case. No codes, no nothing. With literally no fault codes from INPA, ISTA + and my Foxwell NT510 scanner, I decide to change the mechatronic seals, new solenoids and ZF fluid.

I've been scouring the interwebs for weeks now and the go to fix for stuck in Park symptoms on the ZF 6HP series is to change that seal. Mine had 50k and I had just refreshed the fluid and filter with ZF pan and Liqui Molly fluid based on stellar reviews over on FCP Euro. While waiting for my Solenoids to arrive from The CTSC, I drain the fluid and decide to install the Sonnax Zip Kit and use Lifeguard 6. The Liqui Molly came out pretty dark for only 120 miles, which brought up that advice, "Don't change your high mileage Transmission Fluid," and "Only use Lifeguard 6." It definitely seems like it flushed the system because the Lifeguard 6 is coming out very clear.

Flash forward - I install everything, follow fluid fill procedure and no joy. I'm still trapped in Park. In fact, I cannot go through the gears for the recommended 2-3 seconds 6 times during the fill. The shift lever will only spend 2-3 seconds out of Park before snapping back into place. When doing the fill procedure it is common for the first few shift attempts to pop back to P while the fluid works into the gears, but after a few cycles you can shift and hold all gears for 2-3 seconds. This never happened, but I did get about 7 liters of Lifeguard in, though it seemed to take forever for the transmission fluid temperature to get to the right range. Still no codes and no movement. Any ideas?

habbyguy

Are you certain that the Mechatronics plug is properly seated. Contrary to what I read (and sadly, believed...) it's quite possible to engage the white plastic lock without fully seating the connector. And when it comes loose, you get all sorts of odd behavior (though usually codes).

The visual clue that the plug is loose is a gap of more than about 2mm between the plug's lockring and the transmission housing.

And FWIW, "don't change your transmission fluid" is probably the worst possible advice for an E60/61 owner (even if it's directly from BMW - though of course ZF says the opposite, and should know better). ;-) But I'm always a fan of using ONLY the manufacturer-recommended fluid for a transmission. I recall reading that low fluid level will cause the lever to pop back into P, but it doesn't sound like that's likely to be your problem.

longroofe61

Thank you habbyguy for the response. I checked the plug, again, to confirm the correct 2mm gap and I reconnected the plug for good measure. No change. I rescanned the car and found a few GWS codes I perhaps overlooked; E094, E095, and A838, though it seems they were generated during the fluid fill procedure. They cleared and have not returned.

I'm totally down with OE recommended lubricants, twas a moment of weakness. As I fell deeper down the ZF BMW rabbit hole I realized the extent of my mistake. My comment on not changing old transmission fluid referred more to the notion floating around that original fluid was holding everything together and replacing it would throw things out of wack. However, this didn't even apply in my case and it made no sense in this context. Anyhow, if there's anything I've learned on this deep dive it's that ZF and ZF only should be trusted to guide the service of your transmission.

habbyguy

I'm assuming that you've verified that the connection to the shift lever mechanism is attached / aligned properly (done during the Mechatronics fix).

If this problem started with the Mechatronics fix, I'd suspect that the rectangular seal was either defective, the wrong part, or installed "wonky". Since the problem happened immediately before the fix, it really doesn't make sense that would be the issue (though of course, it's possible for the original seal to fail catastrophically - I suppose - and then the new one to have issues, but it's a really long, long shot).

If it was my car, I'd ... well, I'd be curled up in the fetal position sobbing - but after that, I'd probably find a used Mechatronics unit and swap it out. The problem almost has to be in that unit, and shotgunning it with a used part might be the most expedient option (relative term in this case).

longroofe61

Yes, I did, though after the immobilization. I dropped the transmission to do the rear main seal and wondered why there was so much play in the cable. There wasn't, but I closed the gap, from 2mm to flush. I corrected that early on. I believe that will give you Park issues, but not damage anything.
It started at 120 miles after my overhaul. The only transmission work I did was the fluid and filter change, I didn't drop the mechatronic. Post immobilization I dropped the valve body thinking it could be the bridge seal with 50k on it. It seemed fine - was disappointed, frankly, but the 4 tube seals did show significant wear, i.e, flush with mating surface and shorter than new.
After that didn't do anything, I installed new solenoids, zip kit and fluid, still no joy. And no codes. I've dropped the valve body several times now, double checking seal alignment, Park solenoid engagement.
Lol, you don't know the half of it - my mom hit a curb in my E70, slashing the tire and also rendering the car completely immobile. That has 5k on new seals, solenoids and fluid. Initial codes pointed to the GWS, replaced that, codes disappeared but no movement. Starting to think it might be a broken axle or related to the crazy staggered 275/315 wheels. I must have done something horrible to run so afoul of the ZF BMW gods. So yes, two immobilized BMW's showing similar symptoms, no codes.
That said, they have the same valve body, too bad neither transmission works.

I'm starting to think it might be the actual transmission body, oil pump or TC - much to my horror. Thank you for your input and ideas.