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      09-28-2017, 11:02 PM   #1
kdog_x
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ATC 35L Transfer Case Rebuild

Rebuilding the ATC 35L Transfer case, here it is completely assembled... First step is to remove the 3 bolts holding the guibo joint to the output flange.



Once the guibo joint is removed, there is a snap ring which must be removed from the output shaft



Followed by a shim



From there the output shaft should come right off. In my case I had to do a bit of prying with a wood block and a few taps from a rubber mallet. The output shaft on my transfer case was shot, here you can see the teeth sheared off on the inner edge.



The front output flange can be pulled out with a little rocking. There's a locking ring on the end of the shaft that holds it in





The input shaft was better than the flange but appeared a bit worn as well, the original plan was to replace it but a 3-4 week lead time from Germany and that option was sidelined. Although the part has still been ordered in case I end up doing another teardown.



Popping the two halves of the case apart took some doing. There are two squared off slots where you can pry with a large screwdriver, but they use some seriously sticky gasket maker. Be careful not to damage the case since it is made of aluminum and you don't want to gouge the machined surfaces.



Once apart, the small gear that drives the front driveshaft can be removed. The rear bearing is pressed onto the shaft, the front bearing is pressed into the case. As such, you should be able to wobble the gear out with rear bearing attached.



The rear bearing is pressed on and must be removed with a bearing splitter. A good local machine shop could do this for you as well.



Here's the gear after bearing removal



From here the plastic oil slinger cover and a plastic tube can both be removed





From here we can pop off the snap ring securing the clutch assembly, followed by the washer





Then the top plate



Then there's a needle bearing of sorts



Then the actuator ring comes off, note that this must be reinstalled in the same position it is removed. Dont lose the 3 ball bearings that sit underneath this piece.


Last edited by kdog_x; 09-29-2017 at 10:56 AM..
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      09-28-2017, 11:03 PM   #2
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Now we can remove the last cover over the clutch discs



Then we can pull the clutch plates out of the assembly. These are interchangeable, but they must be aligned with each other, and they must go friction plate - steel plate - friction plate - steel plate... etc





Here's an image with all of the plates removed. When reinstalling the discs, the holes in the plates go over the grooves visible in the bottom



There's a large locking ring that holds the whole shaft assembly in. This can be spread with pliers or lock ring pliers and then the shaft can be removed along with the center gear/bearing assembly





This is where I ran into a little problem. I didn't have snap ring pliers large enough to remove the ring securing the main input shaft bearing from this side. After messing with it unsuccessfully for an hour I just took the shaft into my local machine shop and had them remove the bearing and press the new one on for me. With this removed, you should be able to separate the gear / drum from the main shaft and replace if needed.



Removing the shaft had some repercussions for me, in the process I knocked the top of the clutch assembly to the ground and broke the plastic oil guard... time for an adult beverage break



As this piece is apparently irreplaceable and not available as a spare It was necessary to plastic solder it back together. This actually worked surprisingly well. I did not use any filler material though because I did not trust it, but the original material fused nicely.



At this point you're pretty much disassembled other than the case bearings. There is one for the front ouput shaft and one for the rear output shaft. The front bearing is a blind hole bearing, so you can only access it from one side.





I don't own a blind hole bearing puller so for the case bearings, I removed and installed them by heating the case around the bearing. (Heating expands metal)

Keep in mind this is Aluminum, so don't go crazy or you will warp it. At about 205 degrees, the case could be tapped (not with the hammer in the picture!) and the bearings will come out easily.



For replacement, I heated to the same temp and used an appropriate sized seal driver to tap them back in.





The seal driver also works great for well... driving seals. Here's the rear driveshaft seal reinstalled most of the way. It goes just past flush with the surface, it's not all the way down in the picture. A light oiling will help it go in smoothly, you will need a seal puller to avoid damaging it if you go too far.


Last edited by kdog_x; 09-29-2017 at 12:11 PM..
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      09-28-2017, 11:10 PM   #3
kdog_x
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For reassembly, most of the steps above can just be followed in reverse. Just a few points...

The center gear needs to be installed with the main shaft gear at the same time, there's not enough room to install them separately. Here you can see I installed the main shaft and had to pull it back out.



Also, Don't forget to install the plastic oil sump pictured here, I had it almost completely reassembled when I saw that piece on the table and had to pull everything back out to put that in. Notice it's missing above lol



Make sure the snap ring for the main shaft is seated all the way around and squeeze it together to confirm



When reassembling the clutch assembly, a couple of clamps is necessary to squeeze everything tight enough to reinstall the snap ring.



I used RTV Black for sealing the two case halves back together. I'm sure the German spec calls for something else. 12-24 hours drying time is probably a good idea



Once sealed, the halves can be aligned and tapped together with a rubber mallet.



There are two different lengths of torx head screws used to seal the unit. My crude drawing specifies what goes where. I think I torqued to about 15 lb-ft in a star'ish pattern, though I didn't find an official torque spec anywhere.



Almost done, onto the fun part, reassembling the output flange. Here you can see my old beat up flange next to my new one



When you order a flange, you get a bunch of shims, each one is 0.1mm thicker than the last...



So I figured, just measure the old shim to start with right?



Turns out, the old shim size was way too thick to get the snap ring back on for me. Here's where the fun starts. You have to start with a shim that is too thick, and then work your way down one by one until you find the thickest one that can be snapped in. (Keep in mind these don't just slide on easily, and the output flange has to be pried back off each time to remove them. Probably not the worst time to open another adult beverage This took me about 5 tries and about 45 minutes)



And that's pretty much it. The case held a maybe 600mL of fluid. I filled it under the car, but you could probably do it on the bench and just check it once installed. BMW instructions say to drive 600 ft and then recheck the level again. I did this, but the level didn't change. YMMV

When reinstalling the transfer case, Weicon Metal-Free High Temp Anti-Seize is called for on the transmission output shaft. I ordered a bottle (which arrived 3 weeks later, difficult to find in the US), but luckily the output flange comes with a small tube of the stuff which was enough for this job.

You should reset the transfer case adaptations using the ISTA+ software when this repair is complete. Not sure what would happen if you left this step out, but it makes sense that it may need to relearn some things.

Last edited by kdog_x; 09-29-2017 at 01:00 PM..
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      09-28-2017, 11:12 PM   #4
kdog_x
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So, BMW Quoted me $5700 for the repair. My total cost (excluding labor obviously)

Driveline:
Front Driveshaft torx screws - 26117529387 - $1.95 ea x 4 = $7.80
Rear Driveshaft Hex Bolt - 26117527475 - $6.49 x 3 = $19.47
Rear Driveshaft Guibo bolt - 26117635643 - $5.86 x 3 = $17.58
Driveshaft Locking Nut - 26127536563 - $1.98 x 3 = $5.94

Total: $50.79

Transfer Case:
BMW Transfer Case Oil - 83222409710 - $46.66 x 1 = $46.66
Oil Plug - 33117525064 - $7.60 x 1 = $7.60
Rear Flange Assembly - 27107593440 - $230.34 x 1 = $230.34
Rear Output Shaft Oil Seal - 27107546667 - $33.38 x 1 = $33.38

Total: $317.98

Internal Bearings, for a full rebuild you would need 4 bearings, more if you replace the thrust bearings on the center gear, but I did not replace those:

Front Shaft 6008C3 x 2 = $21.99 x 2 = $43.98
Rear Shaft 6009C3 x 1 = $19.99
Input Shaft 6210X5NC3 x 1 = $29.99

Total: $93.96

Grand Total: $462.73 excluding shipping for parts, which was probably around $80 since I used multiple sources. If I was able to obtain the input shaft in the USA I would have which would have added $200 to the total. Not too bad as far as I'm concerned... still a bit cheaper than buying a used unit and having it freighted... and more reliable in my mind.


There's a great exploded view of the transfer case in this PDF on page 25, for any other parts that may be needed.

http://www.fzth.de/fileadmin/user_up...e_2018_web.pdf

Last edited by kdog_x; 09-29-2017 at 12:58 PM..
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      09-29-2017, 10:03 AM   #5
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Awesomesause!!! More pics of the clutch pack assembly, please. Especially the piston, if you have them. Ideally with the piston removed, to see if there's any material that could be machined off to be able to additional clutches. Damn, I just need to buy a spare 8AT w/TC already.
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      09-29-2017, 12:54 PM   #6
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Quote:
Originally Posted by hardparker View Post
Awesomesause!!! More pics of the clutch pack assembly, please. Especially the piston, if you have them. Ideally with the piston removed, to see if there's any material that could be machined off to be able to additional clutches. Damn, I just need to buy a spare 8AT w/TC already.
That's pretty much what I have above, hope that helps. What would adding extra clutches do? Add more torque?
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      09-29-2017, 01:22 PM   #7
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Great work
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      09-30-2017, 08:48 AM   #8
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Very nice.
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      09-30-2017, 09:36 AM   #9
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One of the best write ups I've seen. Thanks so much for your contribution. Out of curiousity, what to you do professionally?

Good to hear that they prescribe goop on the output shaft. The flange definitely looks like a cast piece.

The clutch basket looks like it might hold another clutch pair. Hard to tell. The piston looks like it might have room for another friction and steel, but I'd have to examine one more closely in person. Looks like 5 pairs of frictions and steels and they don't seem to have any problem with wear. Still, an extra clutch pair might gain someone a little more rear drive bias.
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      09-30-2017, 11:34 PM   #10
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Quote:
Originally Posted by hardparker View Post
One of the best write ups I've seen. Thanks so much for your contribution. Out of curiousity, what to you do professionally?

Good to hear that they prescribe goop on the output shaft. The flange definitely looks like a cast piece.

The clutch basket looks like it might hold another clutch pair. Hard to tell. The piston looks like it might have room for another friction and steel, but I'd have to examine one more closely in person. Looks like 5 pairs of frictions and steels and they don't seem to have any problem with wear. Still, an extra clutch pair might gain someone a little more rear drive bias.
I work in field service for medical equipment. So I'm not quite an expert on transfer cases by any means (actually this was the first one I've ever pulled apart), but I have always worked on my own cars, so I have a little experience turning a wrench.

I think getting another pair of friction discs in there would be tight unless you could grind down the bottom of that clutch basket assembly or something. It took quite a bit of clamping force to get that snap ring on it as it is. These cars have so many computers and sensors though that I would think the computer system would start correcting on you if it sensed that there was more rear drive bias.
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      10-04-2017, 08:18 AM   #11
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Awesome post! Thanks for your time in doing so...
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      10-18-2017, 05:46 PM   #12
kdog_x
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I'll add, I dont run a staggered setup, noticed that was being tracked in another thread. But I do switch between 19" wheels with summer only tires and 18" stock wheels with A/S tires for the winter. Not sure if that would contribute to transfer case wear, but I would hope not. I did end up getting the main input shaft from a place in England, so if she goes back out I'm ready. Fingers crossed that doesn't happen 4k miles and going strong
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      10-18-2017, 10:12 PM   #13
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Amazing post, thank you!
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      02-25-2018, 04:44 PM   #14
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Impressive, nice write up.
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      03-17-2018, 02:31 PM   #15
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Very awesome post! Thank you. People like you are the lifeblood of the DIY community.
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      03-26-2018, 08:27 PM   #16
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So do I understand that the main problem was the stripped splines on the output flange? Could you just replace this one part and have things functional again?
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      03-26-2018, 10:24 PM   #17
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Quote:
Originally Posted by CO_Steve View Post
So do I understand that the main problem was the stripped splines on the output flange? Could you just replace this one part and have things functional again?
I'm new to this site and recently purchased a 2014 F31 N47 that needed a transfer case after 20k miles of ownership.

My car's original transfer case had a part number of 27107507374-01 dated 20-09-13. When I removed it the output flange was stripped, just like OP in this thread. I purchased a new one from FCP, and a seal, for $320. I didn't like the condition of the splines on the shaft (too worn out) so I decided to call my local BMW dealer to see if they could do anything. In short they couldn't, but they have a "fixed" transfer case, PN 27108643149 with a 5yr warranty for $1041.60, plus core charge of $1083, and it was in stock so no shipping. I returned the FCP order and bought the new TC from dealer. I installed the TC myself in 8 hours, and had the dealer reprogram the ECUs to accept the new TC for $263.

All total the new TC, rubber mount, with programming cost $1375 plus tax, and my labor. For the price, it wasn't worth trying to rebuild it. At the time the OP posted, BMW was in denial. That's changed now, I was told the new TC is updated and the part is covered for 5 years, as well as the price being lowered. (EDIT 6/18/2019 The BMW dealer ownership has changed and they are telling me the TC warranty is only 2 years, not 5 years).

Hope this helps fellow xdrive owners. Seems that Magna Steyr used material that was too soft for the output flange. It also seems that all ATC 35Ls will have this issue. Hopefully the updated TC solves the issues.

I'll add some pictures when I figure out how......

Last edited by OneLapper; 06-18-2019 at 08:02 AM.. Reason: Pictures
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      03-27-2018, 06:18 AM   #18
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OL, thanks for the update. That's certainly an improvement. My car is a CPO so I'm under warranty until 2020, hoping it fails before that. Another question. After install could you drive the car before it was programmed? I live three hours from a dealer.

In denial, I think that's one of the steps on the way to class action settlement.

Last edited by CO_Steve; 03-27-2018 at 06:30 AM..
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      03-27-2018, 07:24 AM   #19
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Quote:
Originally Posted by CO_Steve View Post
OL, thanks for the update. That's certainly an improvement. My car is a CPO so I'm under warranty until 2020, hoping it fails before that. Another question. After install could you drive the car before it was programmed? I live three hours from a dealer.

In denial, I think that's one of the steps on the way to class action settlement.
After I installed the TC, the car immediately had a Chassis Stabilization warning. The car drove just fine, but AWD, etc, was disabled by the ECU. I drove it for a couple of days while I tried to figure out how to solve the issue. I'm a ex TDI owner and know how to get around them with a laptop, but the BMW is new to me and I don't have all the tools or time to figure out adapting new ECUs.

To any Xdrive owners that have found their way to this thread, you should know that my car developed the occasional "skip" while accelerating. I immediately assumed it was the problem that the OP here identified, but I will say it was difficult to nail down bc the car felt fine 98% of the time. I didn't have another Xdrive car to compare it to which made it more difficult to diagnose. Now with the new TC, the car drives seamlessly, at all times, even in 8" of fresh snow I never feel the AWD kick in as before.

I guess what I'm saying is, if you're reading this and you're questioning why your Xdrive feels a little odd, it's quite likely the TC. The good news is you can fix it yourself for $1500 if you can do some moderate wrenching. For those that cant or wont do the wrenching, the job should cost about $2000 less than it recently did.
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      03-27-2018, 11:39 AM   #20
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Quote:
Originally Posted by OneLapper View Post
I'm new to this site and recently purchased a 2014 F31 N47 that needed a transfer case after 20k miles of ownership.

My car's original transfer case had a part number of 27107507374-01 dated 20-09-13.

...In short they couldn't, but they have a "fixed" transfer case, PN 27108643149 with a 5yr warranty for $1041.60.

...That's changed now, I was told the new TC is updated and the part is covered for 5 years, as well as the price being lowered.
This got me checking RealOEM. I can't find the 27107507374-01 TC PN anywhere. RealOEM says your original TC was a 27108643149, and that PN was used on 328dx cars till 7/2015.

LCI 328dx cars have PN 27108643150 for the TC. RealOEM doesn't say this one supersedes the 27108643149, which tells me that the design could be pretty different and not swappable (even though both have the same PNs for the input/output flanges). I wonder what was changed for the LCI TC now...

Looking at the database, BEM-S4's the only LCI car to have a failed TC. I wonder if he's calling the Dinan Sport tuner the "Dinan Stage 1" tune on his car.

Last edited by FaRKle!; 03-27-2018 at 11:45 AM..
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      03-27-2018, 09:23 PM   #21
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Here are some photos...... Note the part number on the new TC.




















Last edited by OneLapper; 03-28-2018 at 09:44 PM..
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      03-27-2018, 09:33 PM   #22
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Interesting! Yes, on another forum (German) I was advised that there was a rebuilt TC available like you're saying, but I couldn't find it in the states, and couldn't wait that long to ship overseas. If mine goes out again I will probably just do another rebuild, I was able to get the main output shaft from a vendor in England. FCP will supposedly warranty replace the output shaft flange, so it'd be a $150 build doing all the bearings again.

I considered sending out the output flange to be hardened at a machine shop, but if they have designed a better part maybe that's not necessary. for those that aren't familiar with a press, or just don't have the time, it sounds like there is a viable alternative now. So thats
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