[lloyd99]

Short version of my question: I am nearing 50,000 miles for my 2021 X7 M50i. Is it a bad idea to proactively change fluids (transmission, transfer case, front differential, rear differential, and coolant) to help prolong the life of the vehicle?

Longer story and longer version of my question: I am nearing 50,000 miles for my 2021 X7 M50i. Based on various posts, I was thinking of proactively changing some fluids to help prolong the life of the vehicle. I was thinking of doing: transmission, transfer case, front differential, rear differential, and coolant. I am not having any specific problems. I am NOT knowledgeable on car details or mechanics myself. My skills and talents are in other areas. Having said that, I have heard/read others (in this forum and elsewhere) say that changing these fluids can significantly help extend the life of a vehicle. And a friend of mine who is a long-time auto mechanic says the same.

So I stopped by my local BMW dealership and asked the SA for some prices. I didn't want to be surprised if/when I drop off the vehicle for these services. He wasn't very committal, and simply said "about $300-$400 each." And then he said he didn't think they would even change the transmission fluid. He said they have seen changing the transmission fluid introduce problems, and they typically won't do it if there isn't a problem with the vehicle. He said the transmission is "lifetime" fluid. I joked and said "Yeah, when it dies, you'll say the transmission fluid lasted its lifetime. I am trying to extend its lifetime."

I have always had my service done at the BMW dealer. I felt they know this vehicle the best since they work on them all day every day, and honestly, its very conveniently located and they always give me a loaner. However, since I wasn't feeling too confident in this specific visit to the dealer, I went ahead and stopped by a nearby European indy shop. I asked about service and pricing. They did give me specific prices (transmission=$400, transfer case=$450, front diff=$300, rear diff=$200). They were not too different than the dealership "ballpark" numbers. A mechanic happened to visit the front desk while I was there. I struck up a conversation with him. He was all for changing the fluids, told me stories, and cited examples. He seemed very credible.

So my question is: Is it a bad idea to proactively change fluids (transmission, transfer case, front differential, rear differential, and coolant) to help prolong the life of the vehicle? I am looking to prevent future problems and extend the vehicle's life, not introduce new problems. Thanks in advance!

[TurtleBoy]

Some will say they should be changed, some will say problems can be caused by changing them (especially for transmission) and some will say change them but it likely will do no good.

If you feel comfortable having them changed and think it will lessen the chance for problems in the future then there is no reason not to change them.

[admranger]

I'm a 'change the fluids' guy. I have no specific data to back up doing it, but I do it anyway. I am a DIY guy so my labor is free. My only costs are the fluids and my less than precious time since I'm retired.

I changed the diffs and transfer case fluids on my X3 M40i and X7 40i at ~30k and ~25k respectively. All fluids looked dark, especially the transfer cases and front diffs.

I plan to do the transmission service (fluid and filter) at 60k miles. My understanding is that dealers won't do this so you'll be at your independent shop.

Coolant is something I have yet to breach in my decision making. It won't hurt to change it (other than your wallet), but the cooling systems seem to be very touchy with bleeding them properly. If your independent shop has the proper software for the bleeding procedure (which they should have), then this isn't an issue. Remember that you have two separate cooling systems: One for the engine and one for the intercooler.

[keg97]

I changed the diff's and the transfer case on my wife's at about 70K miles. If I had been paying attention, I'd have preferred to do it earlier.

[Kostyan]

If you read on some older bmw x models forums, folks are saying transmission fluid needs to be replaced somewhere between 60 and 90k mi. If you dont replace it prior to that then better leave it alone.
Transmission and other fluids you have mentioned can be changed over at the same time unless you have been towing, racing, or spending a lot of time in rough traffic. You will see that quite a few x7 owners chose to change diff and transfer case much sooner. I personally changed mine because of experiencing slight shudder in low speed turns. If you are not experiencing anything like that then you dont need to do anything until higher mileage.

[wheela]

I changed all those on my X1 and will do the same on our X7 m60i. Lifetime fluids... If you look up ZF (who makes the transmission) they recommend changing the transmission fluid (and replacing it's filter) something like every 60K miles or 7 years, whichever comes sooner. You're right about lifetime - depends what you consider how long the lifetime to be, lol.

For transmission, you shouldn't have an issue with replacing the fluid (drain and re-fill), it's a fluid flush that CAN be problematic, if you wait too long. For a flush, my understanding is they actually connect to a machine that forcefully flushes fluid through the transmission. The issue there is if you're high miles and haven't been doing fluid changes, that the flush can dislodge accumulated deposits that would otherwise have stayed put, and these can potentially migrate and clog up in other areas. Just draining and replacing the fluid has a lot less risk of dislodging debris that would otherwise stay put. Especially if you change the fluid on time. So definitely do the transmission service, but I wouldn't recommend doing a flush.

[TurtleBoy]

Originally Posted by wheela

I changed all those on my X1 and will do the same on our X7 m60i. Lifetime fluids... If you look up ZF (who makes the transmission) they recommend changing the transmission fluid (and replacing it's filter) something like every 60K miles or 7 years, whichever comes sooner. You're right about lifetime - depends what you consider how long the lifetime to be, lol..

ZF recommends changing it at 93k miles.

[wheela]

Originally Posted by TurtleBoy

ZF recommends changing it at 93k miles.

The video from ZF that I saw said 50-75k miles, but that was for 6hp (which BMW also said was lifetime fluid) not the 8 speed. I'd imagine 8 and 6 speed would be very similar.

[TurtleBoy]

Originally Posted by wheela

The video from ZF that I saw said 50-75k miles, but that was for 6hp (which BMW also said was lifetime fluid) not the 8 speed. I'd imagine 8 and 6 speed would be very similar.

That is old/not relevant information. For the new transmissions it 93k miles.

"ZF automatic transmissions are generally filled with lifetime oil. However, due to the many fac- tors influencing the service life of transmissions in individual operation, ZF recommends an oil change after 150,000 km for its transmissions."

https://aftermarket.zf.com/remotemed...fluid-8-it.pdf

[wheela]

Originally Posted by TurtleBoy

That is old/not relevant information. For the new transmissions it 93k miles.

"ZF automatic transmissions are generally filled with lifetime oil. However, due to the many fac- tors influencing the service life of transmissions in individual operation, ZF recommends an oil change after 150,000 km for its transmissions."

https://aftermarket.zf.com/remotemed...fluid-8-it.pdf

Thanks for sharing!

[streborx]

Is "proactively" changing fluids when you change fluids before a gearbox fails? New fluid can cause problems? Does BMW put used fluids in new cars to avoid problems? Or is new oil is OK with a new gearbox, but used gearboxes only work with used oil? What are you guys talking about?

[keg97]

Originally Posted by TurtleBoy

ZF recommends changing it at 93k miles.

Seriously 93K miles? Not 90? Not even 95K?

So much for rounding for ZF!

[TurtleBoy]

Originally Posted by keg97

Seriously 93K miles? Not 90? Not even 95K?

So much for rounding for ZF!

I rounded the number, it is actually 93,205.68 miles. That would be 150,000 km.

[messfong]

The front diff runs really hot, you should change that one for sure!

[lloyd99]

Originally Posted by wheela

For transmission, you shouldn't have an issue with replacing the fluid (drain and re-fill), it's a fluid flush that CAN be problematic, if you wait too long. For a flush, my understanding is they actually connect to a machine that forcefully flushes fluid through the transmission. The issue there is if you're high miles and haven't been doing fluid changes, that the flush can dislodge accumulated deposits that would otherwise have stayed put, and these can potentially migrate and clog up in other areas. Just draining and replacing the fluid has a lot less risk of dislodging debris that would otherwise stay put. Especially if you change the fluid on time. So definitely do the transmission service, but I wouldn't recommend doing a flush.

I have a follow-up question: I am thinking of changing fluids for the transmission, transfer case, front differential, rear differential, and coolant. It is important for me to specify the "drain and re-fill" instructions for ALL of these fluids? Or should any be "flushed"?

[chefwong]

I would add brakes to you list while you're at it, if it hasn't been done in the last 24+ months.

For the trans, I would do a pan drop+filer+ fluids.

The rest are basically straight exchanges - drain out, fill in.

Are you planning to use a Indy or Dealer. Any decent Indy will do it by the correct procedure of bring the fluid to temp when refilling and or using their scan tools to cycle the ABS pump as well.

[wheela]

Originally Posted by lloyd99

I have a follow-up question: I am thinking of changing fluids for the transmission, transfer case, front differential, rear differential, and coolant. It is important for me to specify the "drain and re-fill" instructions for ALL of these fluids? Or should any be "flushed"?

I think transmission is the only one to say no flush on, I believe all the other services are just drain and refill.

[admranger]

Originally Posted by messfong

The front diff runs really hot, you should change that one for sure!

This is no joke. It took over an hour for the front diff to cool down enough for me to only get 2nd degree burns dealing with it after driving to my buddy's shop. Only 1/2 kidding. F. diff fluid was the worst looking of all of them.

[lloyd99]

Originally Posted by chefwong

I would add brakes to you list while you're at it, if it hasn't been done in the last 24+ months.

For the trans, I would do a pan drop+filer+ fluids.

The rest are basically straight exchanges - drain out, fill in.

Are you planning to use a Indy or Dealer. Any decent Indy will do it by the correct procedure of bring the fluid to temp when refilling and or using their scan tools to cycle the ABS pump as well.

Thanks for the reply. I did have the brake fluid replaced at 40K miles.

I am debating between the dealership and indy shop. The price wasn't too much difference, so I am leaning towards the dealership (avoid any potential finger-pointing issues, plus I get a loaner vehicle).

[saveferris199]

What fluid does everyone recommend to replace OE TC and Diff fluid ?

[chefwong]

Stick with OE. It's not alot 1QT , 2QTs.

[keg97]

Originally Posted by lloyd99

Thanks for the reply. I did have the brake fluid replaced at 40K miles.

I am debating between the dealership and indy shop. The price wasn't too much difference, so I am leaning towards the dealership (avoid any potential finger-pointing issues, plus I get a loaner vehicle).

Makes complete sense to me. I'd want a pretty noticeable price savings to use an Indy shop v. the dealership.