[Jack M.]

This t-case works in a completely different way than the Japanese units we upgrade and service. The Japanese t-cases use a ring and pinion, and a hydraulic pump to push a piston in order to actuate the clutches.

This unit has 3 helical gears and a mechanism which uses a motor that directly drives the system to actuate the clutches.

I would gather from the posts in this thread that the t-case is not the problem, but that cog interface which drives the gear and moves the clutches. In the picture below, you can see how the Limited Slip Diff (LSD) works. To the right, you can see a small incomplete gear on top of a larger gear which the cog unit attaches to and moves. When that gear is turned, the scissor looking unit to the left is moved and applies pressure to the clutches. The more the scissors are moved outward, the more LSD action as the clutches have more pressure applied to them. You can see by the shape of the wheel that it will move the scissors apart and inward depending on the position.



So when the cog unit turns the gear clockwise, it creates more friction at the clutches. When it turns counterclockwise, less friction, so you get less LSD action.

The cog unit is a separate assembly from the t-case, so I'll try to get one of those and see what the deal is with it. I would imagine that it is always moving around and doing something, especially in high powered applications where the unit needs to work harder in order to keep traction at the wheels.

I see no plastic parts in this t-case, so the cog unit must contain those weaker parts.

For some reason, I was supposed to get 2 different t-cases, but only this one showed up. I'm trying to figure out where the 2nd t-case went and I'll also work on getting the cog unit.

If someone could please break this t-case and share some pictures of the damage, it would help greatly. Carl, you're local, just break it already!!

Thanks again all!

Jack

Originally Posted by pits200

Jack, awesome pics but stop being such a pansy, it's only a piece of metal going through your hand.

Just kidding! Hope you're doing better.

As for the t-case, I thought the people with failures said it was something to do with a worm mechanism. Overall, I agree that all those pieces seem to look pretty heavy duty.

Your work on this is fantastic. Maybe you can relate some t-case failures that you've seen with other platforms and see how those weak points relate to the specific xi parts.

[pinky_and_me]

Originally Posted by nailer335

If I recall correctly, a worm/cog interface was said before to be made of a type of plastic and could benefit from being made of a stronger material?

There is a picture of this in post 21 here http://www.e90post.com/forums/showthread.php?t=710244

Also if you google "Transfer Case Actuator potential free fix!" you will find a post on another site that has some pictures from an X3 actuator motor failure but I don't know if ours is the same.

[Kalud]

Originally Posted by nailer335

If I recall correctly, a worm/cog interface was said before to be made of a type of plastic and could benefit from being made of a stronger material? I'll look into this more for better detail unless someone else wants to beat me to it with a post explaining this in further detail.

Thanks Jack M!

See those pics of the more common problem with the cog unit.

http://www.bimmerfest.com/forums/sho...d.php?t=566880

[Kalud]

The X3 has a replacement already:

Also an ebay listing for a bronze replacemetn gear:

http://www.ebay.ca/itm/BMW-X3-X5-X6-...ht_1113wt_1188

Pics:

[Jack M.]

Well shoot... I guess that solves that problem with the gear. Anything else which could be an issue for these t-cases?

[pinky_and_me]

Originally Posted by Jack M.

Well shoot... I guess that solves that problem with the gear. Anything else which could be an issue for these t-cases?

Part number (27107546671) for e90 is different than the x3 and it seems different looking at the picture on ECS tuning's site.

[Carl Morris]

Hey Jack, thanks for all the info. I'll see what I can do about breaking one :-).

One additional thing that's been talked about in regard to these is that supposedly the ECU can control the locking action you describe above but so far nobody has found the control in the code. Even if they do I'm not sure what they plan to do with it besides maybe make a special mode that disables AWD for dyno and drift purposes.

You know me, I'd like a little more. In your fooling around if you see an obvious way to create a 3-way switch so that a person could choose RWD, stock, or locked that might be a popular thing...not sure if there'd be a way to sell it, though. I know I'd love to be able to just lock the thing at the dragstrip.

[Slops]

Originally Posted by Kalud

The X3 has a replacement already:

Also an ebay listing for a bronze replacemetn gear:

http://www.ebay.ca/itm/BMW-X3-X5-X6-...ht_1113wt_1188

Pics:

But does this fit our cars? Doesn't say its a e9X? Isn't bronze a hard and brittle material... I would rather want the carbon fiber re-inforced one if I had a choice i guess.

[Kalud]

Originally Posted by Slopp

But does this fit our cars? Doesn't say its a e9X?

No it doesn't fit, but its an example of how it fixes the problem on the X3 which looks prone to fail more from what it looks like searching a bit... Most of the failed transfer case I've seen reported in various bmw forums are those plastic worm gear that gets worn out over time from moving from the exact same path over and over until all the plastic is consumed... Some think that it it a bad idea to replace these by a metal part as if for some reason the transfer case refuses to move internally (the scissor action) then that plastic part is the weak point of failure and it would fail much nicely than forcing the transfer case mechanics... But is this really a concern? I dunno...

[Jack M.]

I'm sure it would be very easy to manipulate the motor which controls the LSD action in the t-case, but the problem is the ECU will very likely freak out if it was unable to control the LSD in they way it wants to. Is there a way to shut that OFF, so the ECU is not monitoring the unit? If so, I can very likely design and build a circuit which will allow the driver to control the LSD manually by either going full ON or full OFF.

Full ON would be nice for drag race use. Full OFF may be a bit tricky and I'll have to take a closer look at the clutches to be sure they will not be damaged if you were to run the car in a way where the front or rear wheels would move independently for extended periods.

I know the ACD unit in the EVOs will burn up the clutches if you have the wheels turn at a different rate for too long, even if the system is OFF and no pressure is applied to the clutches.

Originally Posted by Carl Morris

Hey Jack, thanks for all the info. I'll see what I can do about breaking one :-).

One additional thing that's been talked about in regard to these is that supposedly the ECU can control the locking action you describe above but so far nobody has found the control in the code. Even if they do I'm not sure what they plan to do with it besides maybe make a special mode that disables AWD for dyno and drift purposes.

You know me, I'd like a little more. In your fooling around if you see an obvious way to create a 3-way switch so that a person could choose RWD, stock, or locked that might be a popular thing...not sure if there'd be a way to sell it, though. I know I'd love to be able to just lock the thing at the dragstrip.

[Carl Morris]

All I know is that people have played with pulling the fuse that controls the transfer case (and other things) and they have gotten the RWD behavior that they wanted but there are a lot of undesirable side effects due to other systems that have also lost power. I didn't think that the ECU was sensing the results of the TC control, but you might be right. I don't think anyone has done it for long enough to know if there is an issue like you describe with the EVO.

[Jack M.]

Found the salvage yard forgot to ship my 2nd t-case I ordered, so I should see that one in a couple of weeks now.

Ok, I'll buy a cog unit and see what it looks like and if I can make anything to give manual control over it without pulling a fuse. I'll also see if we can design and build a better gear for it if it is in fact a weak link which can wear out and break. If you are willing to try it, Carl, we can. If we end up burning the t-case clutches, it won't matter as I have 2 more in perfect shape anyway now...

[Carl Morris]

Cool. I'm definitely willing to try it, but I don't want to hack up my interior for a switch like I would have with the Galant. If you can think of a good way to hide a 3 way switch in my interior I'll give it a try. Maybe the glove box...

I need to figure out which clutch I'm going to use first, though. I need a new one by spring. I don't know if you got my email regarding dual mass flywheel questions?

[X.X.I.V]

I'll be willing to test on my car too..(got to do something with my warranty)
I can find a way to make a 3-way switch to go in one of the blank areas by the heated seat switch

[pinky_and_me]

Originally Posted by Carl Morris

I'm definitely willing to try it, but I don't want to hack up my interior for a switch like I would have with the Galant

I put the 3 way switch and an LED for my lazer jammer right below the cigarette lighter under the radio. It fits perfect and you can always replace that plastic part with a stock one if you want to remove it.
Plus the switch is hidden if you close the lid.

[nailer335]

Originally Posted by mario0573

I'll be willing to test on my car too..(got to do something with my warranty)
I can find a way to make a 3-way switch to go in one of the blank areas by the heated seat switch

I like the idea of using one of the blanks between the heated seats for this, that would be subtle and functional, utilizing something thats already there and available.

[Jack M.]

Carl, no I didn't get your email. I'll try to give you a call.

OK, so it sounds like we have some things to work on here. I'll update as the parts come in and what I can do. I am just waiting for the parts to show up at this point...

[Quebequer]

Originally Posted by Jack M.

Carl, no I didn't get your email. I'll try to give you a call.

OK, so it sounds like we have some things to work on here. I'll update as the parts come in and what I can do. I am just waiting for the parts to show up at this point...

Which parts?!

[Kalud]

Early report, I've got a defective 2008 335xi transfer case motor in my hand and I checked it out. I will make a better set of pictures, but most importantly the worm gear is made of metal. It differs from the report of plastic worm gear on the X3.

[Slops]

this is very interesting...

[pits200]

The more I see, the solider the transfer case looks.

[Jack M.]

Wow, I wonder what a metal analysis would find for that. I would be willing to bet it's not very well treated.

Looks like a lot of the grease flung away from the worm gear. Is it dry around the worm gear area as if the grease went away? I'm surprised that they didn't allow the gear oil from the t-case to splash into the unit and use that as lubrication instead.

It will be interesting to see what the used one looks like that I ordered too. Sounds like that is your t-case issue which needs to be addressed. Luckily that is something which can be easily removed if a modification were to be made.

Jack