[F32Fleet]

Originally Posted by fe7565

There are multitudes of comments and videos on this contradiction... Comments below to help me (and others in the same situation) to navigate in order to make a decision.

Most dealers will advise against touching high mileage transmissions with no history of fluid changes. This seems to be related mostly to liability issues in case a dirty/worn transmission dies after a flush or fluid change. Hard to explain to the customer what may have happened. So they just refuse to do it, or charge unrealistic prices to deter you or to cover their ass.

Until about 100K miles in my car, I was on the fence about taking BMW's "lifetime" transmission fluid statement seriously vs the ZF transmission maker's 62K miles guide. Since then I have been reading up on it, and this is what I gathered one is facing with a 113K miles (183k km) car...which is already 83K km's over the ZF's service limit.

Do not flush, unless you replaced your transmission fluid every 30k miles or so, or you usually drive on mostly highways at moderate speeds. A dirty transmission would not benefit from a flush as the dislodged sludge and solids may clog the delicate oil passages/solenoids. So, you should know your car's history.

What about changing it when already over 100K miles? The best (insurance) would be to take a sample of the transmission oil, and send it in for analysis. If it comes back fairly healthy then changing should not be an issue at all. In a normal transmission oil change (vs flush) you are replacing at a 70/30 ratio (70 percent new/30 percent old remains).

I plan to [...]

Years ago ZF recommended every 8yr or 55k-75k miles for cars which were run on autobahn, used for towing or sporty driving. They revised that recommendation to vehicles with unknown history.

The YT video goes back to their old recommendation.

I always go every 50k miles on my ZF ATs.

[ctcarbonari]

Originally Posted by Chihuahua

Just to add to this thread, thectsc.com is a great resource for ZF service parts. I've used them several times with multiple cars and they've been great every time. No affiliation, just a happy customer.

+1 to ^this^

[agentorange]

I'm just glad that I live in the desert and the ZF8 is so much better than the transmission they put in the E30. I had a transmission go bad in the UK on a used, low miles, fully dealer maintained, E30 because of typical British short journeys and the humidity. They were notorious for picking up too much water in the tranny fluid and killing the lock-up clutch due to insufficient pressure. The BMW dealer (!) recommended an independent guy to fix it. When I told him it was fully serviced as per BMW, he said, "That's the problem. BMW don't know how we drive here." If you caned them every day on the motorway like the average salesman, it wasn't a problem.

At least out here I know moisture won't be an issue. Dust? Maybe, if it could find a way in.

[fe7565]

Originally Posted by fe7565

Thank you for posting your experience, service plan, and the oil analysis tests. The analysis tests certainly give a peace of mind going forward. I am still on the fence, if I should do one in a few days when I will replace the fluid/pan at the first time at 113K miles. I am not planning to keep the car forever, but it certainly make a god second car. I wish I would have read up and educated myself on the "BMW lifetime" paradox years ago when I had a lot lower miles, because I would have replaced the fluid/pan a log time ago.

One note that seems to be missed by many, and also brings up a question to anyone who can clarify it, is this step of the ZF decision-chart where they mention cars with a trans cooling circuit where the thermostat opens at 75C. This circuit contains another 0.5 liters of fluid. So ZF says to over fill with 0.5 liters while replacing the fluid. Is that circuit (hoses) empty after draining? That's why the overfill by half liter? Because it that half liter of old fluid is still inside that circuit (hoses) locked behind a thermostat that only opens above 75C, then we have just overfilled the entire system by a half liter.

I think the difference between the second flow chart when replacing the trans fluid vs first flow chart when filling up after repair (i.e bone dry) is that when the trans is bone dry then the 0.5 liters in the cooling line behind the thermostat is not available for fluid to flow until after 75C when the thermostat opens up and 0.5 liters can flow in. So 0.5 liters more then needs to be added in. While if you only drain/refill then that 0.5 liters still remains locked inside the cooling line.

[fe7565]

Yesterday I replaced the transmission fluid. Setting up the car level and jacked up on a sloped driveway was the biggest challenge, took me almost 2 hours. But since I’m getting older, I realize that I only have one life to lose …so I was extremely careful with triple layer of safety. Overall, it was about four hours.

My transmission pan had a stamped date of 2012 May. The fluid was in remarkably good condition. In my opinion, there was no thick deposit sludge or solids, nor anything that I could see that was caught by the magnets. The new pan came with three magnets, and I was reading that somebody else transferred one from the old pan to make it four, and that’s what I did as well…although I’m pretty sure ZF knows what they’re doing.

I used ISTA* in ECU diagnosis variables to monitor the temperature. I estimated about 5 1/4 liters out. I had a mechatronic sleeve replacement with me, but decided not to do it because the transmission electric connector was bone dry, and I wasn’t confident about pushing and pulling hard-accessible sleeves in contorted body positions. That was a mistake.

I believe I have a leak inside the electrical connector where the pins are. I fixed a while back a PT CAN line error that caused communication problems on the PT CAN bus between the transmission, the gear shifter, and the fuel control module. I was missing a PT CAN signal between the transmission and the gear shifter. I bridged to a nearby identical signal wire that solved the problem back then. https://www.bimmerpost.com/forums/sh...php?p=29897190

But this same problem resurfaced again after filling up the transmission, so I believe the fluid being filled/over filled and splashing around inside gets inside the trans connector pins and temporarily shorted them out because the mechatronic sleeve leaks. States shirted until the fluid eventually flows back down and that opens the short between the pins. I will post separately on this soliciting confirmation and advice.

I also changed the rear gearbox oil, which was also in remarkably great condition in my opinion for 113K miles. Took out about 0.7 liters

[Burko]

I was told never flush and only change fluid if you're having issues.

[fe7565]

Originally Posted by Burko

I was told never flush and only change fluid if you're having issues.

Yes, that’s what I thought for the last 10 years as well. How wrong I was. I rather trust the manufacturer’s recommendations who made the transmission.

[F32DieselFan]

Originally Posted by F32Fleet

Years ago ZF recommended every 8yr or 55k-75k miles for cars which were run on autobahn, used for towing or sporty driving. They revised that recommendation to vehicles with unknown history.

The YT video goes back to their old recommendation.

I always go every 50k miles on my ZF ATs.

Sounds good. I`ll going to Change some Fluids on mine in the next few Days.
140K Kilometers now, so it shouldnt be to bad..

I decided to Change the xDrive and rear Axle Fluid aswell so everything is in good condition. Front Axle is already done due to the typical N57 Problems wich required to unmount the complete front...

[swagon]

I just changed my ZF8 oil at 37k miles and 4 years. It was clean, but better early than too late.

Differential oils and transfer cases are also very important to service.

[princeq]

I am planning to flush the gearbox this year.
Currently around 38k miles.

Or do you think just to change it is enough?

[fe7565]

Originally Posted by princeq

I am planning to flush the gearbox this year.
Currently around 38k miles.

Or do you think just to change it is enough?

I am not an expert, but based on my experience with my 113,000 mile transmission:

At 38,000 miles if you want to be super careful, send a sample of the transmission fluid for analysis and then decide.

The danger with dirty sludgy transmission fluid is that when you flush it, the sludge and solids could get caught up in the delicate passages and the solenoids

In my opinion, unless you were tracking with the car or exclusively driving it in bumper-to-bumper traffic, your transmission fluid should still be in excellent condition. Therefore flushing it will not hurt it. But, is it really necessary to flush?

Flushing it will not hurt anything at 38k, but in my opinion is just an unnecessary extra work and a low-yield effort. In the best case, you will improve 70%-80% new fluid to 100% new fluid. I believe that replacing your fluid 70-80% every 50- 60,000 miles or less will provide you the same or very close protection to constant flushing.

But for a piece of mind, and for the experience, flushing would definitely be fine, albeit unnecessary. Of course, you should still replace your transmission filter.