X5 50i Transfer Case Rebuild

[Koer]

Hey guys,

So two weeks ago my X5 started making this weird jerking feeling when turning and accelerating at low speeds, considering i only have 70,000 kms i was surprised when i disconnected the Transfer Case from underneath the car and the problem disappeared. Seems to be VERY common, just have not seen a lot of it in this forum. I hope this is of use to you as this fix is probably the best thing you can do before considering buying a Rebuilt one or even worse.. a new TC.

Seeing as the cost of this repair at my dealership was close to 4000 USD and im no longer in warranty, i decided to have my local shop open the thing up.

This is for the ATC45L Transfer case, i think the 35i version has a smaller TC, and a different design.

First you will need the internal parts. You can get these from Cobra Transmission, i have not seen any other sites that sell them, but the part numbers are always the same anyways. Just make sure they are not used parts.

Products
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1 x BMW ATC45L Transfer Case Seal Kit (TSK-ATC45L / CT01571RX) = $79.99
1 x BMW ATC45L Transfer Bearing Kit (BK-ATC45L) = $179.99
1 x BMW ATC45L Transfer Case Chain (ATC45L-700) = $259.99
1 x BMW ATC35L ATC45L Clutch Pack (ATC45L-100K / CT01361RX) = $269.99
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next you will need 2 liters of BMW TF 0870 or DTF 1 Oil





I did not do the replacement of the parts myself, my local shop did it and im sure a lot of places with experience with TCs are able to do it, its quite a simple mechanism.

Here we can see the TC ready for dissasembly


Inside the TC, lots of residue in the magnets, lots of solid residue in the oil
Clutch pack has signs of wear and is quite loose inside the casing






Chain is in good shape but will be changed aswell.

Here you can see the new clutch packs installed, bearings, seals and chain. Everything goes in smoothly and rotation of the main axle is unrestricted





In past designs the servo motor had plastic gears which broke or skipped. It seems this TC has revisited this design and the servo now works differently. It does not look serviceable. So leave it be unless the calibration fails as i shall explain later on...

Be sure to that everything is clean before the assembly takes place, the TC should be installed, connected and filled with 2 lts of oil before starting the car.

The part that most shops wont do is the calibration with ISTA+, so make sure you do it yourself or have someone do it.

When installation of the TC has taken place and everything is ready, turn on the engine and put the car into gear, move it slowly back a few meters and then forward. this is to make sure there is no air between the clutch packs and the oil is evenly distributed within the transfer case BEFORE CALIBRATION. Check for any leaks or noises coming from the front axle. Put it in parking with the parking brake on. Switch it off and connect your computer and open ISTA+.
With the ignition on (engine off) and connected you should see an option to calibrate the TCA under VEHICLE MANAGEMENT - SERVICE FUNCTIONS
Select POWER TRAIN - Transfer box transmission control unit - Transfer box (VTG): calibration.
It should read out the current calibration parameter (just one) and if you continue it should make a couple of noises as the servo calibrates to the new clutch packs and oil density. The new calibration parameter should appear and it should finish successfully. If this process fails. Move the car again a bit more and try again. If not, the you either have a servo problem, or if the servo is functioning correctly, the clutch packs were not assembled correctly.

After this if you want you can reset transmission parameters to have everything back to factory parameters to test for any further problems. Clear all codes and restart the vehicle. You have now successfully saved 3k on a new tranny. Well done!

[smashe]

This is awesome! Pretty sure my TC is on its way out. Do you have a link to where you bought the parts? What did the shop charge you to rebuild? I'm assuming you brought them the transfer case?

[turboawd]

These transfer cases really need the fluid changed more often. Especially considering it only takes a half quart.
Your old clutches didn't look bad. You think the dirty oil could have been your problem?

[Sophisticated Redneck]

Ty for the post, nice to see whats inside. I got lucky with mine so far with just a oil change and recalibration as it was so bad it throwing a torque point request not met code which means it kept making the truck feel like it was towing a trailer that was jerking it back rapidly. After oil change and recalibration its good now but I have no doubt I will be rebuilding it soon as I have over 150K on it. Oil that came out was pitch black.

[Koer]

Originally Posted by smashe

This is awesome! Pretty sure my TC is on its way out. Do you have a link to where you bought the parts? What did the shop charge you to rebuild? I'm assuming you brought them the transfer case?

Have a look here, this supplier is from the US i believe..
https://cobratransmission.com/index.php?main_page=advanced_search_result&search_ in_description=1&keyword=Atc45l

Make sure the parts are for the ATC45L, there are other suppliers in europe but dont know of them personally.

The shop removed the TC from the car aswell because it is a bit of a hard part to get at, the exhaust had to be unmounted as well as some other parts. They charged me 400 us for the whole thing because i literally gave them everything they needed to get going and calibrated it myself.. It took them 5 days to get everything done.

[Koer]

Originally Posted by turboawd

These transfer cases really need the fluid changed more often. Especially considering it only takes a half quart.
Your old clutches didn't look bad. You think the dirty oil could have been your problem?

I know! At first sight the clutch pack looked fine but then the metal plates were completely scratched and warped, kind of like the clutch assembly on a manual gearbox looks when its been overheated by slipping.

And you are right, more often than not these "non serviceable" parts could very well be saved by changing the oil at the right time, given you know when that time is and calibrate it every time the oil is changed. The rest would simply be failure due to normal wear.
Maybe i'll get this oil changed in 20,000 kms and see how much residue is in it.

[Koer]

Originally Posted by Sophisticated Redneck

Ty for the post, nice to see whats inside. I got lucky with mine so far with just a oil change and recalibration as it was so bad it throwing a torque point request not met code which means it kept making the truck feel like it was towing a trailer that was jerking it back rapidly. After oil change and recalibration its good now but I have no doubt I will be rebuilding it soon as I have over 150K on it. Oil that came out was pitch black.

Dont worry, it wil give clear signs when/if it starts to fail. Plenty of time to start ordering parts by then.

Its funny because instead of TC error codes my truck sent a lot of steering rack and traction control failures.. Seems the erratic behavior of the TC triggers the car into thinking its losing traction in the front axle.

[GuyFawkes]

Will these parts fit the E70 50i??? When I checked with the dealership, they didn't mention all of these parts... Also, if I'm getting the jerking motion at slow speeds, am I beyond the hopes of an oil change helping the situation?

[Sophisticated Redneck]

Originally Posted by E70Q8

Will these parts fit the E70 50i??? When I checked with the dealership, they didn't mention all of these parts... Also, if I'm getting the jerking motion at slow speeds, am I beyond the hopes of an oil change helping the situation?

I have a E70 50i and oil change plus recalibration in ISTA did the trick. Try this first it's cheap and easy before attempting a rebuild, the transfer case actuator motor is extremely sensitive to clutch pack wear, especially if you are running tires slightly out of spec, recalibration and oil change is the first thing to do before not going further. I have not found any scanners that can do the recalibration, only BMW's ISTA works.

[ProjektAutoScott]

Originally Posted by E70Q8

Will these parts fit the E70 50i??? When I checked with the dealership, they didn't mention all of these parts... Also, if I'm getting the jerking motion at slow speeds, am I beyond the hopes of an oil change helping the situation?

No, the E70 has a different case, ATC700 for you I believe. The dealer does not officially support a rebuild or repair of any TC. Notice how there are also no parts listed on realoem. Cobra transmissions, and AWD tech are the goto sources.

Koer, was the shop able to determine the exact mode of failure in these cases? It sounds like it's a clutch pack concern, rather than failed splines, chains, or bearings correct? My T case is coming out this weekend for a rebuild, fluid change, and reset. I have a nasty slip/tugging situation under partial throttle at speed, and a clunk when cornering slower. It was pretty easy to narrow down after unplugging the connector for a test drive. I'm going to repair the case at my shop, and I'll probably make a video to go with it.

[Koer]

Originally Posted by ProjektAutoScott

Koer, was the shop able to determine the exact mode of failure in these cases? It sounds like it's a clutch pack concern, rather than failed splines, chains, or bearings correct? My T case is coming out this weekend for a rebuild, fluid change, and reset. I have a nasty slip/tugging situation under partial throttle at speed, and a clunk when cornering slower. It was pretty easy to narrow down after unplugging the connector for a test drive. I'm going to repair the case at my shop, and I'll probably make a video to go with it.

I think with a bit more research and time you would be able to narrow it down a lot more to which part failed first. The reason i went all out on the new parts is that the cost of changing all the parts is far lower than rebuilding the TC two times in one lifetime due to uneven wear on different parts.

Just FYI, the chain was also loose due to strech, dont know if that much slack is normal but new one was tight as could be going in.

In some cases the Clutch casing itself gets damaged, fortunately this only happens in extreme cases and was not the case with me.

Bearings and seals were ok, but never hurts to get those o-rings and fittings in there since disassembly can always damage them.

Make sure to move the car a bit back and forth before calibrating the TC with new parts and oil so that there are no bubbles between the clutch packs.

[smyles]

Impressive, but curious, why 2 litres are needed, when the ATC45L capacity is <1 L?

[jerrit03]

I am having the same issues with my 2011 50i, but think I am going to try changing the fluid before moving forward with a rebuild. I plan to use 1L of the BMW DTF1, will it take 2? Any suggestions for a suitable alternative fluid? Also, this transfer case only has 1 plug used for draining and filling, so the fluid will need to be siphoned out? Thanks for the help.

[smyles]

Yes, you'll need to craft a /\ shaped tube to get to the bottom, esp. if you don't remove the cross-member. And it will take ~0.7l of fluid. I'd stick with OEM DTF1 - an Atlantic City dealer sells on ebay for $39+tax.

[ProjektAutoScott]

Sorry, I was too rushed to make a video or get too many photos.

Just wanted to update anyone who is into this thread. I ended up pulling my ATC45L from my 2016 50i, and replacing the clutches/steels/clutch springs from cobra transmission. If you have any experience with gear-sets, or transmissions you'll have no problem with this job. I wouldn't recommend opening your TC if you don't have experience. It's not too complex, but there are some unobtainable internal parts you'll be working with, and if you break, or lose anything it's over for your TC. You also can't do this job without access to ISTA, or someone who can reset your TC adaptation

Findings: fluid was very dark and slightly burned. The clutch pack looked like it had gotten real hot from slipping over time. My chain, and all corresponding sprockets and teeth were all in good shape, no sign of chain jump. All three sets of splines were also fine. I didn't touch any seals, tensioners, or bearings they were all just fine.

You only need to remove the output flange on the TC to open the case. You'll need the torx bit, a 3 jaw flange puller, and a STRONG set of snap-ring pliers. When I reassembled the TC I used Victor Reinz 559526008 as sealant, and then applied about 25NM to the case fasteners in a star-like pattern.

Reinstalled, new fluid, and carried out the transfer box adaptation procedure in ISTA. Drives perfect now. Feel free to reach out if you have any questions. If you are nervous about it, take it to a transmission shop.

It was about $300 in materials to do the job

1L of DTF-1, and the clutch/spring kit from Cobra.

[Koer]

Originally Posted by ProjektAutoScott

Sorry, I was too rushed to make a video or get too many photos.

Just wanted to update anyone who is into this thread. I ended up pulling my ATC45L from my 2016 50i, and replacing the clutches/steels/clutch springs from cobra transmission. If you have any experience with gear-sets, or transmissions you'll have no problem with this job. I wouldn't recommend opening your TC if you don't have experience. It's not too complex, but there are some unobtainable internal parts you'll be working with, and if you break, or lose anything it's over for your TC. You also can't do this job without access to ISTA, or someone who can reset your TC adaptation

Findings: fluid was very dark and slightly burned. The clutch pack looked like it had gotten real hot from slipping over time. My chain, and all corresponding sprockets and teeth were all in good shape, no sign of chain jump. All three sets of splines were also fine. I didn't touch any seals, tensioners, or bearings they were all just fine.

You only need to remove the output flange on the TC to open the case. You'll need the torx bit, a 3 jaw flange puller, and a STRONG set of snap-ring pliers. When I reassembled the TC I used Victor Reinz 559526008 as sealant, and then applied about 25NM to the case fasteners in a star-like pattern.

Reinstalled, new fluid, and carried out the transfer box adaptation procedure in ISTA. Drives perfect now. Feel free to reach out if you have any questions. If you are nervous about it, take it to a transmission shop.

It was about $300 in materials to do the job

1L of DTF-1, and the clutch/spring kit from Cobra.

Hey! good to know everything went fine. Seems like you did a far better job at it than me, clutch packs alone are so much cheaper than the whole list of parts.

I don't know who needs to hear this but guys, please calibrate your TC after you do ANYHTING to it, be it oil change or any other service requirement. it might run fine at first but the symptoms will eventually appear..

Anyways, i am happy to report that 32,000 kms later my rebuilt TC has absolutely no issues and is running as if built from factory.

[Maverik259]

So do you need 1 or 2L? One guy says 2 and the other 1...

[turboawd]

Originally Posted by Maverik259

So do you need 1 or 2L? One guy says 2 and the other 1...

A little over a half quart bottle. 1 bottle is all your need. You need a suction syringe to suck out old fluid. There's no drain plug. Only a fill plug.
Not sure how the op figured you need 2 litres.

[scotty339]

Originally Posted by turboawd

A little over a half quart bottle. 1 bottle is all your need. You need a suction syringe to suck out old fluid. There's no drain plug. Only a fill plug.
Not sure how the op figured you need 2 litres.

Ya its .7L for the ATC45L if doing a drain and fill. The empty volume may be slightly different... but not that much.

OP,
well written. enjoyed reading. my x35i has a atc45l in it.

[Maverik259]

Originally Posted by turboawd

A little over a half quart bottle. 1 bottle is all your need. You need a suction syringe to suck out old fluid. There's no drain plug. Only a fill plug.
Not sure how the op figured you need 2 litres.

Sweet. I figured maybe 2 was needed if it was bone dry?

[ahmad1985]

So i got new transfer case and only got 1 Ltr of DTF1 would it take 1 Ltr or 2 i am confused too here.

[tlow98]

Good read. Thanks for posting, OP.

One question - curious about the TC Calibration and why it’s a necessity after just fluid replacement?

I’ve heard/read both ways across various BMW AWD platforms. Always curious to know the reasoning.