Transmission Service - the High Mileage debate

[tomjonesBT33]

Folks -

My Z4 currently has 224K miles on it and runs/drives great. I bought this car with 214K from my brother-in-law last year, who purchased it new from BMW. I have all of the service records since new. He was very diligent about maintenance with the exception of the transmission fluid service. It's still running the fluid from the factory! The transmission shifts fine -- very smooth in fact. But I like to keep my cars up to date with service, so I'm tempted to drop the pan, install a new filter and refill.

However, there is the ubiquitous debate as to whether you should change the fluid on a high mileage transmission if the fluid has never been changed. The advice goes:

1) if it is working fine, don't touch it - you'll definitely screw it up by changing the fluid and it will start slipping soon.

OR

2) drop the pan, refill (don't flush) and feel good about keeping your car up to date on service. If it starts slipping, it's not because you changed the fluid, but because the transmission was already at the end of its life anyhow.

Just wondering if there is a consensus on this forum as to whether it's a good idea or not to change the fluid at this high mileage point.

Comments welcome.

[Sterling Roadster]

I've often wondered this myself. I can never seem to get a straight answer from even indie specialists. I think the idea of not flushing it is that you have particles of the transmission which act as a filler in between the gears. And when you remove them, it starts to slip. There are additives which have particles for just this issue and I know certain cases have been solved this way. With that mileage however that fluid has been through so many heat cycles it must be not being doing much of what it's supposed to. If it's just for peace of mind I would do the refill like you mentioned. But it's almost impossible to know exactly what's going on in a specific transmission without opening it up.

[rsutoratosu]

Manual or auto ?

[rsutoratosu]

If you have a ZF tranny.. zf is telling you to change your fluid.. I trust the manufacture of the transmission, not the guy that resold it to you and tell you dont touch it

[tomjonesBT33]

Originally Posted by rsutoratosu

Manual or auto ?

Auto. 5-speed

[Vanne]

yeah this is an Auto only question, manual? always change it.

I have often wonderd about this myself as i have various /other/ auto cars, including a 130k mileage 2002 year Z3. Id like to change that fluid too, but have been advised not too.. which i think is rubbish, but who knows??

[LisaLannister]

I changed my manual transmission fluid on my '07 Z4 3.0si when I purchased it this summer and it did make a big difference.

On my '15 650xi Gran Coupe, ZF emailed me directly and told me that they recommend changing the transmission fluid on my 8spd auto at 150,000 km, or 93,000 miles.

[rsutoratosu]

Exactly, when your transmission breaks, BMW will gladly sell you another car. BMW doesn't make the transmission, they know jack about it. That's why getting the real info from the person that made the transmission is correct.. in our case, for auto ZF. They sell the entire kit with filter.

I have 07 with 85k, it will be my 3 time changing and first with new pan and filter this coming spring. FCP euro has life time warranty on them.

[pungo]

Originally Posted by Sterling Roadster

I think the idea of not flushing it is that you have particles of the transmission which act as a filler in between the gears. And when you remove them, it starts to slip.

The gears is not what slips rather the clutches since all the particles that were floating around were improving the friction on otherwise prematurely worn out clutch material because the old overdue fluid was not lubricating any longer.

Always change the fluid at the transmission manufacturers recommended intervals.

[Piper1]

"Lifetime ATF" = when your transmission goes the fluid lasted the lifetime of the transmission. As others have said trust in what the trans manufacture would do when it comes to changes. In that high of miles not being changed there's no telling damage or no done by not doing it until you do, but also as others have said there's kits out there to change it.

[elerner61]

I went through this journey with another automatic transmission vehicle we purchased with 65,000 miles on it, a Jeep Wrangler JK. Had never had the transmission fluid changed. I consulted a number of transmission specialists. In the end the advice was to pull a sample of the fluid (shop did it, can't recall if the vehicle has a dipstick for the tranny) and based on the condition of the fluid decide how to go forward.

The fluid was somewhat darker than new, but it wasn't black. The shop said it should be ok to flush it and that's what I had them do.

Your mileage may vary...

[KevinC]

I would write to Mike Miller @ BMWCCA if you are a member. He tackles questions like this all the time, and I'd trust him implicitly to have the proper answer.

[Efthreeoh]

My sister had 2005 X3 with an auto. She asked me the same question. At 145,000 she had a BF flush and refill of the trans. No issues afterwards.

My opinion is it's just internet myth.

[rsutoratosu]

ZF not really looking to sell you a new tranny, they tell you to change the fluid. BMW on the other hand will look at every chance to sell you a new car.

Yes, on a really old tranny, you might run into issue, but basically when they rebuild it, they clean it out and curse at you

[KevinC]

"old tranny" is not a good visual lol

[T-Bears]

From my experience, new fluid always improved the shifting on my transmissions by at least 20%. Faster shifting and less likely to slip during hot weather. This was on a Tip Boxster, Step Z4, and Speedshift Merc.

It might not always be the case for every auto tranny out there. A flush or refill isn't going to help a transmission with worn bands, clutch packs, and drums.

[tomjonesBT33]

So I decided to do the fluid and filter change. The original oil was dark but did not smell burnt. The pic of my finger shows the new oil for comparison.

Magnets had accumulated a bit of metal as expected. The filter was also dark as expected. But overall, it was much better than I thought it would be.

Cleaned everything up, replaced the filter and gasket and refilled with fresh oil. Followed the instructions from the video from ZF to fill it up. Drove it 30 miles right afterwards and most notable change was that the shifts seemed quicker.

Biggest benefit is that it eases my mind to know it's been properly serviced.

Couple of tips: use an 8mm Allen wrench to break the fill plug free. There is not enough room to usehex bit. Also, the oil pan bolts use a T-27 torx. Not a common size included in most bit kits, so make sure you have one on hand before starting this.

[T-Bears]

Good work! My old oil was dark as well and I ended up stripping the allen key on the drain plug, mine didn't wanna come off but I had to remove the pan anyway for the filter change. Also, I was missing 2 magnets someone must have forgot to put em back lol.

[rsutoratosu]

Nice.. i'm doing mine in the spring. Stored for now.