BMW E46 Project: Rear Differential Swap (from an X3)

[@michaelblacktree]

Since my E46 has an automatic transmission, the rear differential has the 3.38:1 gear ratio. I wanted something a little more aggressive, so I looked for a BMW differential with slightly shorter gearing. The rear differential in the X3 3.0 has the 3.64:1 gear ratio. If you want the 3.91:1 ratio, you'll need to find an X3 with the 2.5 liter engine. Just FYI.

[@FlashTwoSix]

I could of swear the e46 auto gear ratio is 3.46

[@michaelblacktree]

I think the different engines had slightly different gear ratios. But the 3.0 is definitely 3.38. It's written on the diff case.

[@PM_DRIFTING]

@@FlashTwoSix my 323i has 3.07 on automatic tran and 3.23 on 316i

[@lukevmh]

Does this work on m3? would it be possible too swap the ring and pinion only from the e90 or the x3 diff into a m3 diff? does it matter what year x3 we use?

[@MaxMinstats]

I have 2 of the 168k 3.91 x3 diffs if you want one. Idk if its worth it with shipping costs but all I'd want is $80. Your wiring video helped me out. If you get a diff from a zhp auto or 2.5l z4 you can get a 3.64 ratio that is the same type as the 188k e46. The main difference is they use needle bearings instead of ball bearings which are weaker. They make a 3.91 188k in an extremely rare model x3 but it's literally the rarest bmw diff out there. The owner of diffs online has never had a single one pass through his shop the entire time they've been in business. Keep the content coming! There's always something new to learn and I love learning!

[@michaelblacktree]

I didn't know the 3.91 rear diff was a 168k unit. In that case, I'm glad I got the 3.64 rear diff, because it's a 188k unit. I plan to upgrade the engine, and the 188k unit can handle more power.

[@brettkrehling8738]

Thank you for making a quick thorough video, I was going back and forth on if I should remove my subframe, but I’ll definitely use this method

[@michaelblacktree]

No problem. No need to remove the subframe, if you just want to swap rear diffs. Although it would be a good idea to check for cracks where the subframe attaches to the chassis, while you're in there. It's a common problem.

[@driven_nation]

Man I feel like I'm just copying your vehicle choice! Forever ago in college I found your fiero tuft test. Shortly there after got my first fiero. Now I'm looking to change gear ratio in my e46 and here I am again.

[@michaelblacktree]

LOL, so how do you feel about the E46? Personally, I feel like it was a good choice.

[@driven_nation]

@@michaelblacktree it's been pretty low drama. Not the most exciting car I have owned but also not boring. I wish it was like 500lbs lighter but also heated leather seats are too nice to give up for such a small gain. I threw on coilovers, swaybars and 200tw 245/40/17s and it hung mid pack at autocross. With a shorter gear, lsd and subframe refresh I'm looking to make it a bit more competitive. Not as visceral as the fiero but that's fine.

[@michaelblacktree]

That's cool. Mine is about 500 lb lighter than stock, and it made a big difference at the drag strip. Haven't had a chance to autocross it yet. But the gutted interior will probably put me in a different class.

[@tylerpage-howell8116]

Great information

[@michaelblacktree]

Glad you liked it 👍

[@andresvillanueva2291]

Thanks for make this video it help alot. Keep up the good work.

[@michaelblacktree]

thanks! 👍

[@mry82]

Nice! I have never researched what rear diffs would work in the e46. Mine is a 2.5 AWD manual and I don't recall what the ratio is off hand (I imagine you can't just swap the rear diff in an AWD since it has a front diff too...?). When I was having my subframe mounts replaced with powerflex poly I went ahead and got ECS poly diff mounts too. With 62% of power headed to the back that (and other suspension work) really makes the car tight and willing to rotate nicely!

[@michaelblacktree]

That's a good point about the bushings. The Basket Case BMW is going to get lots of new bushings very soon. But I want to take it to the drag strip one more time, before I tear everything apart.

[@mry82]

@@michaelblacktree You may already know, but (I think it is the uppers...) you can replace 2 of the outer bushings in the rear control arms with ball joints (same that go in the bottom outer) instead, and that will also stiffen things up a bit more. I have powerflex lower control arms with poly and poly trailing arm bushings... poly everywhere I could (including FCAs)... with H&R springs and Bilstein sports it is not overly plush, but I don't mind the ride and it really sticks to the road (and some of our western NC roads are a little bumpy)! Take care!

[@michaelblacktree]

I wasn't aware of that bushing trick. Thanks!

[@MaxMinstats]

@@michaelblacktree Moog ball joins from a 91 Toyota camry make perfect spherical metal rtabs for only $40.

[@MaxMinstats]

@@mry82 you have a 3.46 front and rear ratio in your car. Changing diff ration in an xi can get... complicated. If you wanted a 3.64 for instance, you would need a 1st gen pre lci x5 3.0 auto front diff, and a 1st gen pre-lci 2.5l z4 auto rear diff. You can do 3.91 as well, which is what I have, but you need the 6sp manual or it's horrible on the highway. You can also get 4.44 gears, but it's so low it just makes 1st gear useless.

[@Mike-ve3vb]

Great video I’m about to replace front differential flange

[@michaelblacktree]

You need to be very careful with that. The torque on the flange nut sets the preload for the pinion bearing. BMW TIS has a procedure which involves checking the drag on the pinion bearing with a special tool. Or you can mark the nut before removal, and line up the marks when you reinstall it.

[@Mike-ve3vb]

@@michaelblacktree yea ima mark it! you didn’t really use special tools lol, I got 2.93 diff but the flang on mine has a grove indent and the one I bought has a flat flange

[@Mike-ve3vb]

@@michaelblacktree what you torque your nut too !!?? How’s the x3 diff holding up

[@michaelblacktree]

When I made this video I wasn't sure how to correctly install the input flange. So I left out that part, because I don't want to put out bad info. The main point of the video was to show that you can use a rear diff from an X3. (but not from an E90, LOL)

[@Mike-ve3vb]

@@michaelblacktree I’ll just install in the same force it took to get out

[@AxionUK]

So what's with the whole driveshaft confusion on the forums then, one person says you need a 323 shaft, another says 325 is fine and then this 330 works just fine? How come some of the people doing the swap on 330 had to get a different shaft to reach the diff?

[@michaelblacktree]

They're trying to do the swap without changing the diff input flange. Because the nut on that flange has a very specific torque procedure. And if you get it wrong, you could potentially destroy the differential. I left that part out of the video, because I torqued it by feel, and don't want people trying to copy that.

[@AxionUK]

@@michaelblacktree But on the forum the guy said that he originally tried just swapping the flange over but said it still wasn't long enough (which didn't add up in my head to be fair as the CV flange is way longer) and that's why he ended up getting a different shaft and pulling it out

[@michaelblacktree]

I'm not sure what's going on there. Maybe he swapped in a small case diff?

[@AxionUK]

Didn't look like it, it's the kpeng thread I'm talking about

[@dwightfortner2720]

Did you need a specific thin wall 30mm socket? What brand? Great channel.

[@michaelblacktree]

I couldn't find one, so I modified a socket on the bench grinder.

[@WannabeRacer]

Nice! I wouldnt take that on, I'm more of the "I'll just buy aftermarket" kind of guy

[@michaelblacktree]

I'm the kind of person who likes to take something apart, just to see what's in it. So even though the E90 differential didn't work out, it was still a learning experience.

[@WannabeRacer]

@@michaelblacktree I just dont have the space to do it, nor the confidence. If its meant to be destroyed, I love to take it apart to learn about it, but if its meant to be used, I get cautious of breaking it.

[@michaelblacktree]

That's understandable.

[@NeeoDroid]

What year x3 diff are compatible with E46 please ?

[@cbinc24]

07-10

[@NeeoDroid]

@@cbinc24 I actually ended up getting one from a 06 X3 3.91 ratio. Just had to use the output shaft from my e46

[@sosikcodriftingakagaffa_ma2711]

Is this a large case diff ? Are the drive shafts the same length both sides 👌✌

[@michaelblacktree]

It's a medium case diff (188K), just like the E46.

[@imartynenko]

That new diff all covered in oil, could be gaskets leaking, I would’ve replaced those and cleaned a bit, but that’s just my ocd

[@michaelblacktree]

Yeah, the seals are leaking. I held off replacing them, because I wasn't sure if the diff was damaged. But now I know it's good. So when the diff comes back out (for new bushings), I can also replace the seals.

[@JohnFaire]

How's the backlash from putting the drive shaft flange on? Got clunks?

[@michaelblacktree]

I was careful not to crush the crush sleeve any further during assembly. So it's all good.

[@JohnFaire]

Great news! This is one of, if not the main, problem area of swapping differentials. Lots of people, even pro mechanics, do not understand how to transfer a flange from a different unit since they can not rely on counting treads. Usually by feel, like you did, but how do you tell an audience about that. Hard to find on KZbin as well. I go by the break away torque, somewhere around 30 ft/lbs. Rotating torque is small, like 5-10 inch/lbs for the 188m bmw diffs. Glad it worked out for you

[@mattbadley1896]

Hi, how did you get the drive shafts off the X3, I'm trying to do a rear diff poly bush replacement because the rubbers on are shot but can't get decent access to the inverted torque heads 😢

[@michaelblacktree]

I just used a breaker bar. Clearance is tight. I had to put the transmission in neutral, and rotate the wheels by hand to access each bolt. And I used the parking brake to hold it while I loosen the bolt. Then release the parking brake, rotate to the next bolt, etc. It was pretty tedious.

[@mattbadley1896]

@@michaelblacktree thanks, did you need to remove the anti roll bar or load the suspension up to help with the clearance?

[@michaelblacktree]

The sway bar has to be removed. I didn't load the suspension, but you could do that if you want.

[@CheSoZH]

Yee yee

[@michaelblacktree]

hehe

[@mannabatth4092]

How was the result did it make noticeable difference in gearing?

[@michaelblacktree]

In normal driving, the difference between 3.38 and 3.64 gear ratio is pretty minor. But it made the car a couple tenths faster in the quarter mile.

[@tomasbauer816]

And why not differencial from E46 316ti automat? It has the same sizes and ration 3.73 I try it on my e46 320i. Lets see.

[@tomasbauer816]

Oh, you have big differential. Ok. How its works on bmw xi?

[@michaelblacktree]

The salvage yard didn't have any of those. But they had a few X3s.

[@MrJamesshipman]

The 316ti never came to America... Although I guess you could ship one over for Europe.

[@thebattleduddie6180]

I got my mind split are the Differential Output Shaft internal the part that meets the rest of the diff the same on all bmw e46's?

[@michaelblacktree]

Sorry, youtube never notified me of this comment. But yes, I think they're the same. Or at least, all the 188K diffs should be the same. The small case (168) and large case (210) might be different.

[@cheefnap4276]

is there a difference between the 2006 (gen 1) vs 2007 (gen 2) x3 rear diff?

[@michaelblacktree]

I'm not very familiar with the X3. Is the Gen 2 based on the E90 chassis? If so, then it probably has an E90 style differential (i.e. with roller bearings).

[@MaxMinstats]

Yes. They changed diffs to the e9x and e6x style with the n52 engine

[@rondellfortune4311]

Are the x3 differential lsd ?

[@michaelblacktree]

Nope, just a different gear ratio.

[@zacksmith5332]

For the nut at 7:52 How tight do I go? There’s not a torque spec that I can find and if I go too tight, it stops spinning the flange altogether

[@michaelblacktree]

There is some debate on how to do that. Some people say to tighten the nut until the preload on the pinion bearing reaches a certain amount. But that requires removing the ring gear from the differential, to get an accurate reading. It also requires special tools to measure the preload. Another method is to mark the nut before you remove it, and return it to the same spot when you reinstall it. In either case, you have to be careful not to over-tighten the nut, because it'll crush the crush sleeve for the pinion bearing. That will cause excessive play in the diff gears, resulting in gear noise, and eventually diff failure. Over-tightening that nut may also shorten the life of the pinion bearing. I decided not to put any of that info in the video because I didn't want people trying to "torque by feel" like I did, and end up destroying their rear diff. I also didn't want to deal with people arguing on which method is best. People actually do that. There are heated debates on the forums regarding the best method to install the diff input flange. No kidding.

[@zacksmith5332]

Yeah I’ve actually been doing a lot of looking around on them and yeah you pretty much just summed it all up. Right now I’m trying to figure out if the x3 diff uses a crush sleeve or shims for pinion bearing preloaded. I believe you mentioned in the video that your original diff for the swap was shimmed. So Is the x3 diff shims as well?

[@michaelblacktree]

Both rear diffs use a crush sleeve on the pinion bearing. And the snap rings on the side also double as shims for the ring gear. So for example, the snap ring on the left may be a different thickness than the right, depending on how the ring gear needed to be shimmed.

[@zacksmith5332]

Alright that’s really helpful stuff man thank you so much!

[@zacksmith5332]

Also one last question, do you know what the correct turning torque spec would be? Something like 15 inch pounds? I know that’s what it if for some ford diffs

[@johnsmith-gm4kf]

The 3.91 is 168k comes on x3 2.5i auto

[@gravey07]

How do the driveshaft cups come out of the diff?

[@michaelblacktree]

Are you referring to the input flange? I had to use a 2-jaw puller.

[@gravey07]

@@michaelblacktree output flanges. Just popped them out 👍🏼

[@hamzehalnawaiseh1114]

Differential x3 racing ???

[@znaive8563]

How did you take the driveshaft flange off so easily? Mine won’t pull off with all my weight….

[@michaelblacktree]

For some reason, that one wasn't very tight. The other ones needed a gear puller.

[@88-MM]

Can I use x3 prop shaft on e46 330i

[@michaelblacktree]

Not sure. But it probably won't fit.

[@McMarschmellow]

4:07 what kind of boil is that?!

[@michaelblacktree]

Are you talking about the wasp nest? There were lots of wasp nests in the undercarriage. I think it sat in someone's backyard for a long time before I bought it.

[@McMarschmellow]

@@michaelblacktree ah alright, it just looks super weird when you expect a normal case

[@330itis]

You realize you can't just replace the input flange like that right? There is a crush sleve that is a one time use and the nut is torqued up to the right amount of load on the bearings. If you're not a mechanic you shouldn't make videos like this.

[@michaelblacktree]

Yes, I understand that. I also have enough experience to know what I can get away with and what I can't (for the most part). But I encourage you to do things by the book, if you have any doubts.

[@dironizareyes596]

He looks mechanically inclined to me besides great video he used the same nut on the same pinion so torque the nut to where it was will suffice. Yea the book says use a new nut too blah blah blah He wasn’t using a new crush sleeve so he didn’t have to use the crush sleeve torquing procedure. Just mark the pinion and nut relation and don’t go beyond or before that point when tightening. Keep making great vids they’re awesome !!!!

[@michaelblacktree]

thanks!

[@ronanmcgrath1983]

@@michaelblacktree out of curiosity can the crush sleeve be removed from the front of the diff by removing the front seal and sliding it out?

[@HolyShitAccess]

hey, go frak yourself. this video is priceless for some ppl like me.