[Madsen203]

Originally Posted by lumbrjackedpcj

This is all great info, thank you! I plan on changing front diff oil soon. Repair instructions say to replace stiffening plate bolts. Are you doing that? I know some critical bolts are one time use only but do you foresee any issues reusing?

Thank you,

I didn’t replace mine as it isn’t an engine related component such as head bolts where it’s critical to have exact specs.
So far, it hasn’t fallen off. Maybe I’ll replace them in the future but seems a bit overkill as I’m not racing or doing anything to stress this car. Haven’t noticed any difference or odd noises.

[cavalierx7]

Has anyone had seen or read of a transfer case actually failing or is it mostly symptoms at this point?

[RichY]

Subscribed. If purchasing a new X7 M60 would you change all fluids after 5000 miles or 2500 miles. I have not ordered one yet. I would also check fluid levels during delivery before purchase as some have said that the fluid levels were low from mfg.

[Madsen203]

Originally Posted by RichY

Subscribed. If purchasing a new X7 M60 would you change all fluids after 5000 miles or 2500 miles. I have not ordered one yet. I would also check fluid levels during delivery before purchase as some have said that the fluid levels were low from mfg.

Checking fluid level on TC and rear diff is fairly easy. Front takes a little more effort.

I wouldn’t change them but topping them off is a good idea if they are in fact low. I’m going to keep exchanging 200ml of the TC fluid each oil change I do (5k mi) given I can’t fully drain it each time. I’ll do the differentials at 25k intervals.

[Madsen203]

Originally Posted by Madsen203

Checking fluid level on TC and rear diff is fairly easy. Front takes a little more effort.

I wouldn’t change them but topping them off is a good idea if they are in fact low. I’m going to keep exchanging 200ml of the TC fluid each oil change I do (5k mi) given I can’t fully drain it each time. I’ll do the differentials at 25k intervals.

Chat GPT aligns with my original thinking for the TC:

To estimate how long it will take to replace most of the fluid through partial fluid changes, you can use a logarithmic approach to model the dilution process. Here's a breakdown of the math:

### Given:
- Total fluid in the system: 700 ml
- Amount replaced at each service: 200 ml
- Frequency: Every 5,000 miles

Each time you replace 200 ml of the 700 ml, you're leaving behind some percentage of the old fluid. The proportion of old fluid left after each replacement is:

\[
\text{Proportion of old fluid remaining} = \frac{700 - 200}{700} = \frac{500}{700} = 0.714
\]

After each replacement, 71.4% of the old fluid remains. To determine how many replacements (or miles) it takes for the fluid to become mostly fresh, you can set a threshold for what "mostly fresh" means. Let’s assume you want less than 5% of the original fluid remaining.

You can calculate the number of replacements using the formula for exponential decay:

\[
\text{Fraction of original fluid remaining after } n \text{ replacements} = 0.714^n
\]

Set this equal to 0.05 (for 5% remaining) and solve for \(n\):

\[
0.714^n = 0.05
\]

Taking the logarithm of both sides:

\[
n \log(0.714) = \log(0.05)
\]

Solve for \(n\):

\[
n = \frac{\log(0.05)}{\log(0.714)}
\]

It will take approximately 8.9 fluid replacements for the fluid to be mostly fresh (less than 5% of the original fluid remaining). Since the replacements happen every 5,000 miles, the total distance before the fluid is mostly fresh is:

\[
8.9 \times 5,000 = 44,500 \text{ miles}
\]

So, after about 44,500 miles, the fluid will be mostly fresh since the factory build.

[admranger]

No one said there'd be math Madsen203.

[Sat Pat]

This guy maths!

[Madsen203]

Originally Posted by Sat Pat

This guy maths!

This guy leverages AI! ** FTFY


So if one would want to swap fluid, they would have to do it 9 times with a short drive between each exchange.

Or figure out what black magic BMW uses to exchange fluid as they supposedly drain it entirely. I don’t think vacuum is enough to get it all out but I don’t have personal experience with this so I could be wrong.

[GCR]

Originally Posted by Highline-Autos.com

According to Mitchell 1 OEM Labor Guide and Rates, transfer case assembly remove and replace breaks down to the following.

Parts: $5,723.76
Labor: 5.2 Hours

Trenton O. Gibson
tgibson@highline-autos.com
Highline Autos
Direct: 602.909.9216
Office: 480.348.0777

Does not include programming, or installation of the transfer case/transmission mount, which is not transferable from the old case.

[e30 4 life!]

Just a fair warning to folks going to dealer for xfer case service, it is a pita to drain and fill the case properly and follow the ista procedure. Not saying all, but a lot of techs pull out what they can, top it off and call it a day. I was on the phone with friends at the dealer and basically laughed and said, yeah we don't even bother changing the fluid.

Ultimately, they advised me to modify thin brake line bent to a 90 deg angle and ovaling out the end to slip it down deep into the case and extract while using ista to open the 2nd resoivor. Despite how much I love to DIY I went armed with this info to my trusted BMW indy and they let me in the shop to hang out. We ended pulling about 900ml out of the case.

[Guest4now]

Lots of good info here. Saving for research

[Madsen203]

Originally Posted by e30 4 life!

Just a fair warning to folks going to dealer for xfer case service, it is a pita to drain and fill the case properly and follow the ista procedure. Not saying all, but a lot of techs pull out what they can, top it off and call it a day. I was on the phone with friends at the dealer and basically laughed and said, yeah we don't even bother changing the fluid.

Ultimately, they advised me to modify thin brake line bent to a 90 deg angle and ovaling out the end to slip it down deep into the case and extract while using ista to open the 2nd resoivor. Despite how much I love to DIY I went armed with this info to my trusted BMW indy and they let me in the shop to hang out. We ended pulling about 900ml out of the case.

I ended up buying 1/8th inch OD metal tubing to make this as my rubber tubing,
Albeit thin, didn’t fit. I’ll be trying this again tonight.

[admranger]

Originally Posted by Madsen203

I ended up buying 1/8th inch OD metal tubing to make this as my rubber tubing,
Albeit thin, didn’t fit. I’ll be trying this again tonight.

I was wondering if something like that wouldn't be the hot setup. Keep us informed!

[DishoomX2]

Originally Posted by Madsen203

My recent experience:
700 ml in front,
700 ml in tC
And 1L in rear.

How were you able to extract and fill so much on the rear? I had a difficult time using a fluid extractor syringe. The first draw was relatively easy, and I was able to get about 250mL. After that, I had a difficult time pulling the plunger back and couldn't fill it all the way. I tried a few more times with a longer more flexible (smaller diameter) tube, which made it even more difficult. I then broke out the my large fluid extractor but didn't get much more until I took a heat gun and created a bend in the tube. All in all, it looks like I was able to pull out around 800mL or so . I filled until it started pouring out (one full 500mL bottle, plus another 1.5 full syringes worth) -- when I originally removed the drain plug, no oil had spilled out.

Also, unlike some pictures and videos I've seen, my differential has cooling fins and sensor wire plugged into it. Is this unique to M50i or DHP package? I covered it well with a plastic bag before starting the job. I have no idea what that one threaded hole is for (see pic) -- is something missing?

I've done several oil changes and brake jobs before, and although this should have been straight forward, I found it more difficult than I thought it would be. Perhaps I had a tough time extracting because I needed to drive around more to heat the diff oil up?

I wasn't able to get to the front diff today, but don't look forward to it considering I found the rear diff to be a pain.

[Madsen203]

Originally Posted by DishoomX2

How were you able to extract and fill so much on the rear? I had a difficult time using a fluid extractor syringe. The first draw was relatively easy, and I was able to get about 250mL. After that, I had a difficult time pulling the plunger back and couldn't fill it all the way. I tried a few more times with a longer more flexible (smaller diameter) tube, which made it even more difficult. I then broke out the my large fluid extractor but didn't get much more until I took a heat gun and created a bend in the tube. All in all, it looks like I was able to pull out around 800mL or so . I filled until it started pouring out (one full 500mL bottle, plus another 1.5 full syringes worth) — when I originally removed the drain plug, no oil had spilled out.

Also, unlike some pictures and videos I've seen, my differential has cooling fins and sensor wire plugged into it. Is this unique to M50i or DHP package? I covered it well with a plastic bag before starting the job. I have no idea what that one threaded hole is for (see pic) — is something missing?

I've done several oil changes and brake jobs before, and although this should have been straight forward, I found it more difficult than I thought it would be. Perhaps I had a tough time extracting because I needed to drive around more to heat the diff oil up?

I wasn't able to get to the front diff today, but don't look forward to it considering I found the rear diff to be a pain.

40i different diff that is more like a truck rear end and fairly accessible with the tool from FCP.

[lumbrjackedpcj]

Change your fluid folks. I changed the front diff today. 50i has 25,960 miles. Drained approximately 500mL. So about 100mL short. I could definitely see a shimmer in the oil in the sunlight. The service manual only shows 10 bolts that hold the stiffening plate. It had 12 on my car.

[Madsen203]

4mm OD tube

I ordered this to fit into the 6mm tube with the CTA 200ml suction hand pump I had. Perfect fit and no modifications needed.

I was able to fish this much deeper than the 6mm tube and could in theory extract all the fluid. I only had 700ml of fluid leftover from when I first did this 5k miles ago so I pulled 600ml and refilled it until it dripped out.

Fluid was merky brown and looked slightly dirty but could be heat which changed the fluid darker. Alas, now 80%+ of the fluid is fresh.

Used ISTA service function to open reservoir and also do the adaptions reset.

I plan to do this exchange once more at 40k miles (in 10k) but that time, pull all the old fluid out and start totally fresh.

Took about 1 hour start to finish.

I also pulled 400ml of fluid from rear differential and added in 450 (it was a hair shy on last fill after putting a full liter into it). I had the extra bottle laying around so I figured it couldn’t hurt while I was down there.

All in all, worth doing it yourself if you have the flexibility and willing to get a little messy. Not a bad job once you get oriented under the car. No need to remove the TC brace either with the hose and CTA 19->17mm cap tool.

Let me know if you need any other info!

[Madsen203]

Originally Posted by Madsen203

4mm OD tube

I ordered this to fit into the 6mm tube with the CTA 200ml suction hand pump I had. Perfect fit and no modifications needed.

I was able to fish this much deeper than the 6mm tube and could in theory extract all the fluid. I only had 700ml of fluid leftover from when I first did this 5k miles ago so I pulled 600ml and refilled it until it dripped out.

Fluid was merky brown and looked slightly dirty but could be heat which changed the fluid darker. Alas, now 80%+ of the fluid is fresh.

Used ISTA service function to open reservoir and also do the adaptions reset.

I plan to do this exchange once more at 40k miles (in 10k) but that time, pull all the old fluid out and start totally fresh.

Took about 1 hour start to finish.

I also pulled 400ml of fluid from rear differential and added in 450 (it was a hair shy on last fill after putting a full liter into it). I had the extra bottle laying around so I figured it couldn’t hurt while I was down there.

All in all, worth doing it yourself if you have the flexibility and willing to get a little messy. Not a bad job once you get oriented under the car. No need to remove the TC brace either with the hose and CTA 19->17mm cap tool.

Let me know if you need any other info!

PSA: I was having a pulsating braking feel when lightly braking that I chalked up to the regenerative braking.

After changing the TC fluid today, it’s GONE!

Couldn’t be happier with the results.

[Tinbad]

Originally Posted by Madsen203

PSA: I was having a pulsating braking feel when lightly braking that I chalked up to the regenerative braking.

After changing the TC fluid today, it’s GONE!

Couldn’t be happier with the results.

I have the same pulsating breaking feel, even after fresh (rear) pads and rotors. Good to know it may be related.

My TC fluid was replaced last month but the jitter is still there in low speeds as well as brake pulsating. There’s also a harshness/vibration where the car doesn’t feel as smooth over bumps as it used to. Multiple people (foreman, BMW rep) drove it and feel it, but couldnt pinpoint to anything. I wonder if that’s also a related symptom.

Either way made appointment and hopefully they will replace TC this time and it will fix all the issues.

[e30 4 life!]

For those attempting DIY, here is a nice write-up over on the X3m page https://x3.xbimmers.com/forums/showthread.php?t=2119690

[bradythedog12]

hi all - in references to the issues revolving around the fluid… is one of them a kind-of clunking when you turn right (clunk on right front) or left (clunk on left front)? We have a unicorn 2020 M50i with 20,500 miles so very low miles but obviously out of warranty at this point.

I haven’t seen the same issue description so far on this thread so I thought it was time to specifically ask.

Thanks!

John

[Guest4now]

Originally Posted by bradythedog12

hi all - in references to the issues revolving around the fluid… is one of them a kind-of clunking when you turn right (clunk on right front) or left (clunk on left front)? We have a unicorn 2020 M50i with 20,500 miles so very low miles but obviously out of warranty at this point.

I haven’t seen the same issue description so far on this thread so I thought it was time to specifically ask.

Thanks!

John

Typical symptoms are choppiness when turning. Especially slow speed in parking lots.

Have you ever had a 4 wheel drive truck? Its the same feeling as leaving it in 4wd and turning in parking lots.