[anom3]

The procedure is pretty well documented on here as well as youtube but I'll mentioned a few things that are not:

a) Expect to drain / fill just over 400 ml. Total capacity is about double that but due to all the stuff inside, you will only get half. Technically you should do the fluid change at least twice if you want to replace most of the fluid. If you are not getting 400 ml out of it adjust your suction tube or your transfer case is missing some fluid.

b) Torque settings, at least for my VIN:

All 6 bolts holding the transfer case carrier to the chassis : 20 nm
2 bolts holding the exhaust hanger : 28 nm
Main big nut + bolt holding the transfer case to the carrier : 68 nm
Fill plug : 60 nm

c) Sometime in the mid 2010s, BMW changed the fluid. I don't really know the details but this is when it went from "TF-0870" to "DTF-1". The few posts on forums that mention this change say its because they went to synthetic with DTF-1. My concern was that since I am doing a half drain / fill, I will essentially have 1/2 of the old type of fluid and 1/2 of the new type of fluid. This does not appear to be a problem. I just did about 50km on the car and it runs just fine.

d) I did this on race ramps. Major pain in the ass, but it is possible on ramps. Lots of posts saying the car needs to be level etc etc for the drain / fill. Its probably better for it to be level but when I pulled the fill plug only a tiny bit came out (I caught all of it) so I do not expect any issues on that front. Only 50km on the new fluid so far but no issues at all.

e) This gotcha probably only applies to my car but maybe others... 2 of the 6 threads that hold the carrier to the chassis in my vehicle had separated from the chassis. Quite possible someone had been in there before me and used an impact to remove or attach the carrier. Not really ideal but having some JB Weld on hand to reattach them to the chassis might be worthwhile. Just a tiny bit will do because all you need is for the thread to stay put while the bolt catches the thread. Once the bolts grab the threads you should be able to to thread them in while keeping some tension on the bolt. Like I said, probably specific to my vehicle but worth mentioning as this is the only real hangup I had through the whole process.

f) Maybe specific to my particular year + model (2012.10 production 335ix), but I had significantly less room around the big nut + bolt than I saw on the many videos online. So much so that there is no way to fit my torque wrench in there. A ratchet would not fit no matter what. Depending on your model, expect things to look a little bit different than what you see on the 3-4 youtube videos that show the fluid swap. I am talking about the nut side which is basically between the transfer case bushing and your transmission. I didn't bother trying to torque this to exactly 68 nm as I know 68 nm is basically fairly tight but don't break your arms tight. I ended up using an angled wrench to access the nut. Something like this https://www.toolsource.com/images/pr...um/112696b.jpg.

g) Next time I do this (2nd change, in a few hundred km) I will probably remove the exhaust hanger off the exhaust pipe so I can get the carrier out completely. Depending on how hard it is to do so, maybe its worth while as the carrier gets blocked by it so you can't remove it completely and kind of sits there obstructing everything.

h) I highly recommend changing the transfer case fluid if you are over 60-80k miles. You will notice a difference as well as prolong the life of your (expensive) transfer case.

Enjoy.

[johnung]

Originally Posted by anom3

The procedure is pretty well documented on here as well as youtube but I'll mentioned a few things that are not:

a) Expect to drain / fill just over 400 ml. Total capacity is about double that but due to all the stuff inside, you will only get half. Technically you should do the fluid change at least twice if you want to replace most of the fluid. If you are not getting 400 ml out of it adjust your suction tube or your transfer case is missing some fluid.

b) Torque settings, at least for my VIN:

All 6 bolts holding the transfer case carrier to the chassis : 20 nm
2 bolts holding the exhaust hanger : 28 nm
Main big nut + bolt holding the transfer case to the carrier : 68 nm
Fill plug : 60 nm

c) Sometime in the mid 2010s, BMW changed the fluid. I don't really know the details but this is when it went from "TF-0870" to "DTF-1". The few posts on forums that mention this change say its because they went to synthetic with DTF-1. My concern was that since I am doing a half drain / fill, I will essentially have 1/2 of the old type of fluid and 1/2 of the new type of fluid. This does not appear to be a problem. I just did about 50km on the car and it runs just fine.

d) I did this on race ramps. Major pain in the ass, but it is possible on ramps. Lots of posts saying the car needs to be level etc etc for the drain / fill. Its probably better for it to be level but when I pulled the fill plug only a tiny bit came out (I caught all of it) so I do not expect any issues on that front. Only 50km on the new fluid so far but no issues at all.

e) This gotcha probably only applies to my car but maybe others... 2 of the 6 threads that hold the carrier to the chassis in my vehicle had separated from the chassis. Quite possible someone had been in there before me and used an impact to remove or attach the carrier. Not really ideal but having some JB Weld on hand to reattach them to the chassis might be worthwhile. Just a tiny bit will do because all you need is for the thread to stay put while the bolt catches the thread. Once the bolts grab the threads you should be able to to thread them in while keeping some tension on the bolt. Like I said, probably specific to my vehicle but worth mentioning as this is the only real hangup I had through the whole process.

f) Maybe specific to my particular year + model (2012.10 production 335ix), but I had significantly less room around the big nut + bolt than I saw on the many videos online. So much so that there is no way to fit my torque wrench in there. A ratchet would not fit no matter what. Depending on your model, expect things to look a little bit different than what you see on the 3-4 youtube videos that show the fluid swap. I am talking about the nut side which is basically between the transfer case bushing and your transmission. I didn't bother trying to torque this to exactly 68 nm as I know 68 nm is basically fairly tight but don't break your arms tight. I ended up using an angled wrench to access the nut. Something like this https://www.toolsource.com/images/pr...um/112696b.jpg.

g) Next time I do this (2nd change, in a few hundred km) I will probably remove the exhaust hanger off the exhaust pipe so I can get the carrier out completely. Depending on how hard it is to do so, maybe its worth while as the carrier gets blocked by it so you can't remove it completely and kind of sits there obstructing everything.

h) I highly recommend changing the transfer case fluid if you are over 60-80k miles. You will notice a difference as well as prolong the life of your (expensive) transfer case.

Enjoy.

I've got an F30 2015 335ix. It sounds like you went through some bigger procedure than I'm aware of.

On my car, the transfer case fluid change is pretty straightforward. There isn't a drain plug so the old fluid needs to be removed by suctioning it out through the filler hole. See photo.

The only real trick is that a thin suction tip must be used. There are a lot of parts in the way inside the TC so the thin tip must be moved all around to remove the most old fluid. It takes some patience. Typically it takes 650ml-700ml of the new 1 liter bottle (see photo) to refill. So that's about how much can be removed by suction with a thin tip.

I would be nervous assuming that the TC is properly filled on car ramps. It's supposed to be filled with the car level on a lift or on 4 jack stands. Same goes for other fluids.

It doesn't hurt to replace TC fluid often since it will make for a higher percentage of newer fluid in the mix. I do mine every 20k-30k miles or so, when it's convenient, just because something else is being done underneath.

Hope this helps!

[anom3]

that's exactly where I drained / filled from. you are right it is fairly straight forward but working under the ramps and the two broken threads made it quite a pita.

as far as working on the ramps... 400ml came out, 400ml went in. I was super careful to catch everything and made sure not to spill anything when suckling out when it came time to use the suction pump. I'll add that i just had a chance to do some spirited driving and zero issues to report... only positives. I'll be doing it again in a week to get more of the old fluid out.

not sure how u can get 6 or 700ml out. my silicone tubes are 6mm and no matter how I tried to position it, after 400 there was no way to get any more.

Originally Posted by johnung

I've got an F30 2015 335ix. It sounds like you went through some bigger procedure than I'm aware of.

On my car, the transfer case fluid change is pretty straightforward. There isn't a drain plug so the old fluid needs to be removed by suctioning it out through the filler hole. See photo.

The only real trick is that a thin suction tip must be used. There are a lot of parts in the way inside the TC so the thin tip must be moved all around to remove the most old fluid. It takes some patience. Typically it takes 650ml-700ml of the new 1 liter bottle (see photo) to refill. So that's about how much can be removed by suction with a thin tip.

I would be nervous assuming that the TC is properly filled on car ramps. It's supposed to be filled with the car level on a lift or on 4 jack stands. Same goes for other fluids.

It doesn't hurt to replace TC fluid often since it will make for a higher percentage of newer fluid in the mix. I do mine every 20k-30k miles or so, when it's convenient, just because something else is being done underneath.

Hope this helps!

[capt_slow]

Is there any value in dumping the entire 1L bottle in there and let the excess drain out? Just to decrease the concentration of old fluid?

[anom3]

I was thinking about doing just that but decided to do two separate fills instead.

Judging by the overflow that was coming out when filling, it needs to circulate to be worthwhile. The overflow was very clear clean fluid.

Originally Posted by capt_slow

Is there any value in dumping the entire 1L bottle in there and let the excess drain out? Just to decrease the concentration of old fluid?

[Elijah Hua]

Did you do any adaptation through ISTA+? Does changing TC fluid make the acceleration smoother?

[Musashi]

Originally Posted by Elijah Hua

Did you do any adaptation through ISTA+? Does changing TC fluid make the acceleration smoother?

Having spent 7000$ CAD + 4000$ rear and front driveshafts (at east shafts were under a warranty), two refurbished TCs before receiving a revised Magna Steir new one, acceleration issues were the transmission and a faulty ZF solenoid. The TC acted in turns, or in eco mode (to test going uphill), when it tried to change the traction distribution. In the normal 60/40 I do not recall feeling the TC acting up ever even when dead. However, if I tried to plow through snow etc I would feel it shaking. The TC issues also wrecked the driveshafts.

The overall lesson, including insider knowledge conveyed by SC to me, is that they were perhaps OK designed for early X drive generations, but remained the same as cars grew up 1500, 2000 lbs, 180 to 500 Hp. They simply cannot handle cumulative load, finite lifecycles. They are not quite a problem, but a curse. An expensive one. In some cases, the lifespan of a set of tires was the TC lifespan, for others 2 tires = one TYC dead too. I first had issues at 70,000 kms but it was so faint I thought it decaying spring/Adaptive M. In the end, to redesign them properly may be too costly or a substantial change in aspect of part geometry. It is cheaper to warranty them. 7/10 warranties = 7000$ max for BMW NA; if just 3 pay, that is 20k so 13k profit!!! Until sued.

The best BMW garage I know, and it tuned Ms and Porsches for track, told me that there is a direct correlation between vehicle torque, speed, larger wheels, mass and fast TC death. A 328I base may experience few issues. A 340M M, X3 M40 M50 X5 etc, will kill them fast esp if the Traction Control is frequently flashing (rain, ice snow plowing snow). I have a friend whom drove his car too aggressively, tight turns and powered in turns esp before apex, I told him, he knew my story, fried his TC as he should have. So I straighten the wheels then I power it, and try at all costs to prevent skids or slips. So when new Ms came with a Disable AWD option, that is not just to give the car a nice RWD feel, but to save BMW warranty claims...and customer anger.

[gunnerxq]

Originally Posted by Musashi

Having spent 7000$ CAD + 4000$ rear and front driveshafts (at east shafts were under a warranty), two refurbished TCs before receiving a revised Magna Steir new one, acceleration issues were the transmission and a faulty ZF solenoid. The TC acted in turns, or in eco mode (to test going uphill), when it tried to change the traction distribution. In the normal 60/40 I do not recall feeling the TC acting up ever even when dead. However, if I tried to plow through snow etc I would feel it shaking. The TC issues also wrecked the driveshafts.

The overall lesson, including insider knowledge conveyed by SC to me, is that they were perhaps OK designed for early X drive generations, but remained the same as cars grew up 1500, 2000 lbs, 180 to 500 Hp. They simply cannot handle cumulative load, finite lifecycles. They are not quite a problem, but a curse. An expensive one. In some cases, the lifespan of a set of tires was the TC lifespan, for others 2 tires = one TYC dead too. I first had issues at 70,000 kms but it was so faint I thought it decaying spring/Adaptive M. In the end, to redesign them properly may be too costly or a substantial change in aspect of part geometry. It is cheaper to warranty them. 7/10 warranties = 7000$ max for BMW NA; if just 3 pay, that is 20k so 13k profit!!! Until sued.

The best BMW garage I know, and it tuned Ms and Porsches for track, told me that there is a direct correlation between vehicle torque, speed, larger wheels, mass and fast TC death. A 328I base may experience few issues. A 340M M, X3 M40 M50 X5 etc, will kill them fast esp if the Traction Control is frequently flashing (rain, ice snow plowing snow). I have a friend whom drove his car too aggressively, tight turns and powered in turns esp before apex, I told him, he knew my story, fried his TC as he should have. So I straighten the wheels then I power it, and try at all costs to prevent skids or slips. So when new Ms came with a Disable AWD option, that is not just to give the car a nice RWD feel, but to save BMW warranty claims...and customer anger.

What year is your 335i? I've heard that one of the culprits of TC failures is the guibo. The mostly aluminum one transfers too many vibrations and was replaced with mostly rubber guibos. This was a bigger issue with diesel cars though.

[Bilko]

Originally Posted by anom3

that's exactly where I drained / filled from. you are right it is fairly straight forward but working under the ramps and the two broken threads made it quite a pita.

as far as working on the ramps... 400ml came out, 400ml went in. I was super careful to catch everything and made sure not to spill anything when suckling out when it came time to use the suction pump. I'll add that i just had a chance to do some spirited driving and zero issues to report... only positives. I'll be doing it again in a week to get more of the old fluid out.

not sure how u can get 6 or 700ml out. my silicone tubes are 6mm and no matter how I tried to position it, after 400 there was no way to get any more.

Thanks for adding this. I'm completing the same service in a few weeks and will source smaller tube.

[rpg]

Hopefully this might help someone. I was browsing the parts catalog (as you do) and since 10/25 it looks like BMW have now released a tool to introduce a drain plug into the ATC35L. To allow for complete oil changes. Now, it’s very new so isn’t listed on many sites but it looks like it’s very expensive. Part number for kit is 27105B8C3E4. You won’t find on RealOEM by the way as their catalog is only 03/2025, but see attached image for reference.

A bit more searching then brought me to a German automotive tool company that have developed a very similar product:

XXL-Automotive

So I decided to order it (back order, not in stock currently). It’ll be nice to be able to drain the transfer case easily. Worth the extra expense vs trying to extract via fill hole.

[Wires]

What is stupid annoying is our Audi SQ5 has the same transfer case, but it had the drain plugs. Thanks BMW for saving a couple pennies here... And considering eventually all BMW's start leaking from every seal area, I'd risk one more potential leak point with that bung!

But having #8 in that parts kit would be stellar for the drain.

[Wires]

Originally Posted by rpg

Hopefully this might help someone. I was browsing the parts catalog (as you do) and since 10/25 it looks like BMW have now released a tool to introduce a drain plug into the ATC35L. To allow for complete oil changes. Now, it’s very new so isn’t listed on many sites but it looks like it’s very expensive. Part number for kit is 27105B8C3E4. You won’t find on RealOEM by the way as their catalog is only 03/2025, but see attached image for reference.

A bit more searching then brought me to a German automotive tool company that have developed a very similar product:

XXL-Automotive

So I decided to order it (back order, not in stock currently). It’ll be nice to be able to drain the transfer case easily. Worth the extra expense vs trying to extract via fill hole.

Just wondering if you go this yet, and how it was to do if you did.