[BB_cuda]

Notes for Swapping the BMW 215 size differential: 2/11/17

I had a spare 2.81 ratio differential sent to HP Autosport in Santa Barbara, CA. Work was done on my welded diff to convert it over to bolted type ring gear and a Wavetrac LSD was bolted on and proper backlash set to retain same backlash prior to the machining work. thanks Harold and thanks Autotech.

Differential swaps have been covered many times in the suspension/chassis/brakes section of E90post. I will list the basics for getting to the point of directly working on the diff and then provide more details at that point.

NOTE: I cover switching over to a finned differential cover but factory exhaust may have interference with the lower driver's side fins. The 1addicts thread that I attach in post 2 shows how some 1 series and 3 series gassers had to trim the lower left fins some. Post #87 in that 1addicts thread shows an excellent picture of that trimmed cover. My aftermarket exhaust cleared by about 5/8" to 3/4" (I'll go do a final measurement and edit it in), so no trimming was necessary on my part.
torque specs:
• Driveshaft nut, Spec 26 11 1AZ, 85 N-m, 62.7 lb-ft (modify for using crows foot, covered later)
• 1/2 shaft screws, Spec 33 21 1AZ, 70 N-m, 51.6 lb-ft
• Front diff bushings, Spec 33 17 1AZ (12 mm), 100 N-m, 73.8 lb-ft
• Rear diff bushing, Spec 33 17 1AZ (14 mm), 165 nm-m, 121.7 lb-ft
• Diff cover bolts, Spec 33 11 1AZ (10 mm), 90 N-m, 66.4 lb-ft
• M22 fill screw, Spec 33 11 2AZ (22 mm with o-ring), 60 N-m, 44.3 lb-ft
Special tools:
• 27 mm wrench or 1-1/6” box end wrench (for rear side of rear diff bushing)
• 21 mm socket for front side of rear diff bolt head (21 is not a normal size that comes in a socket set)
• 50 mm thin crow’s foot wrench, available from a couple vendors, I borrowed one from generous forum member and will be passing it on per his instructions to next diff installer.
• Transmission jack
• A lift would be quite helpful but I did the job on jack stands (as usual)

PARTS LIST:
• (3) Liters, Motul Gear 300, 75W-90 gear oil(break-in and change after 1000 miles), bought this on ebay, $59 for 3 Liters, free shipping
• 33-32-6-770-288 rear diff bushing nut (M14x1.5 ZNS3). I call this the 0288 nut below, bought from local dealer, Husker has them for a hair less than dealer
• (12) half shaft screws- p/n 33-20-7-572-716 (M10x43 mm long), bought from Husker
• Blue Loctite for the ½ shaft screws, purchased from local parts store
• Insert nut for driveshaft to diff connection- p/n 26-11-7-567-770 (M39x1.5x16.5 mm), bought from Husker
o This comes with a new seal and plastic retainer clip
• Sealant for cover, p/n 83-19-0-404-517, Loctite 5970 liquid sealant, bought from Husker, Typo corrected on 3-14-17
• The following are only needed if you are switching to the finned cover shown in photos
• Finned rear differential cover p/n 33-11-7-519-661 ($128 at Husker site, https://www.bmwdirectparts.com/ )
• Bellmetric 14x1.5X140 mm bolt (10.9 grade)
https://www.belmetric.com/14x15-fine...4jv5u14r9ohop0
• 9/16” ID hardened washer OR 14 mm ID hardened washer (used on 14 mm bolt since it doesn’t have a flanged head), use Bellmetric link above and hunt for it
• 1-1/4” OD x 9/16” ID X 5/8” thick aluminum spacer, machined by local shop, I paid $75
• (1) M10x 25mm, P/N 33-11-7-521-292 (cover bolt, deleting 75 mm for a 25 mm one) see photo, bought at Husker
PREP THE NEW DIFF:
• Built unit was shipped back with cover off
• Check that unit does or does not have stub axle seals and retainers
clips installed. OmahaDZL, Whitbread, and I learned that Autotech as
a default doesn't replace these. Omaha will elaborate in a post below on
his experience and resolution. If no seals and clips installed, STOP and do this BEFORE adding lube and/or installing the new diff.
• Install either original cover or finned cover
• Apply Loctite 5970 sealant on lip of cover, I spread it out sort of thin with finger tip
-original uses (6) 25 mm and (2) 75 mm long screws
-finned uses (7) 25 mm and (1) 75 mm long screws
-torque to 66.4 lb-ft
-I let it cure over night
-load diff with gear oil through fill hole and torque to 44.3 lb-ft with 14 mm male hex.

GET THE STUFF OUT OF THE WAY:
• Supported car on 4 jack stands at normal rocker panel located jack points
• Removed fore to aft support bar of uhaul receiver hitch [Doesn’t apply to stock car]
• Removed under trunk stored compact spare tire [Doesn’t apply to stock car]
• Removed the plate that spans across “floor hump”
• Removed the exhaust’s mid pipe and rear pipes
• My exhaust is very easy to remove because it is 3 piece design.
OmahaDZL still had OEM big motha 1 piece in. He was able to remove
diff without removing exhaust. He sort of rotated it down and it came
down between the pipes. He did have "fun" with the midpipe exhaust
rubber isolators being in his way. These are the ones that are
connected adjacent to the 2 front diff bushing screws. He said after the
fact that he should have pulled those off the welded on exhaust hanger
rods for more clearance. WD40 and channel locks may be your friends
here.. If you do take Omaha's simpler route, be advised this
may possibly run you into trouble for pushing diff back up in there if
you go with the finned diff cover. MEASURE carefully if you 1)don't pull
exhaust and 2) use finned cover.
• Removed the heat shield that spans from back of floor hump plate to
close to aft end of drive shaft
• Per OmahaDZL install experience, the DEF tanks are in the way and
make it more difficult to do the work on the back side of the subframe.
Maybe this isn't a big deal if you're working on a lift. Omaha and i did
this job on jack stands though. Again, I benefited having the DEF tank
"ectamy" already behind me.
ONTO THE DIFF ITSELF:
I used old belts that don’t fit me anymore but you get the idea. Use wire, rope, whatever you have that will support the ½ shafts and driveshaft from falling down after unbolting. I allowed more of a droop for the driveshaft for when I was doing the final pull to achieve an angle to slide out the splines of the diff to driveshaft. There are a couple pictures showing all three shafts being tied up.

I borrowed a transmission jack locally and a 50 mm crow’s foot wrench from a forum member. It is advised to loosen the driveshaft’s 50 mm nut while the half shafts are still connected and the emergency brake is applied. There have been several discussions on the boards about which way to turn the nut to loosen the connection. The nut is threaded onto the driveshaft and it is a normal right handed thread. Thus, if you are looking aftward, the nut will need to be turned clockwise. If you know what right hand rule is, the nut is turned in the direction of your curved fingers and your thumb points in the direction that the nut’s axis advances towards. I have a graphic pasted into the pictures that comes from the online workshop manual. I really struggled here but will spare you and explain what needs to be done to more easily free up the nut.
• CLARIFICATION: Turn the nut from the driver's side to passenger side
when looking from the bottom. This is equivalent to my wordy, techno-
geeko explanation above. To my defense, the graphic below is showing this same thing. Picture is looking aft ward.
• DON’T BRACE WITH THE BI-HEXAGONAL NUT WHEN WORKING ON THE 50 mm NUT! LEAVE IT ALONE!
• Slide the crow’s foot up onto the 50 mm nut with a breaker bar inserted into the ½” drive’s square hole. Skinny guys like me slide a cheater bar onto the breaker bar too.
• Turn the nut as shown in the graphic. You will have to move the crow’s foot many times. I was only able to turn it about 2 revolutions before encountering SIGNIFICANT resistance.
• Turn the nut in the opposite direction about same 2 revolutions. This helps to break up the Loctite that is inside the nut. It turned fairly easy in comparison to previous step.
• Go back to turning in the clockwise direction per the graphic. OMG, it was so much easier to turn in comparison to 2 steps earlier. Eventually, whitish powder started falling from inside the nut and this was great news that the Loctite had been broken up. Continue turning until it’s pretty much freewheeling.

Disconnect the 2 half shafts from the sides of the diff. You will need an E-torx socket here. If memory serves, it is an E-14. I found it easier to put car in neutral with e-brake off. I would turn either wheel to get optimal position on each of the 6 half shaft screws. The optimal spot seems to be with screw at half way point between bottom and top to be able to get the socket on. I held the wheel with one arm while un-torqueing with the other. The passenger side was easier as I was able to hold arm (very large spoke) of wheel to resist the torque. On the driver’s side, I got help from someone to intermittently apply and remove the e-brake as I un-torqued that side. It is sort of weird to try to finesse the half shafts out of the diff’s output flanges. I then tightened the belts to have the half shafts above the diff’s side flanges. This is so they don’t hang it up when it’s brought downward on the transmission jack.

Bring transmission jack under and properly support the differential. I used the ratchet strap to hold it onto the jack as an insurance measure.

Disconnect front differential bushings and remove the long 12 mm bolts. Disconnect the rear bushing that uses a 14 mm bolt. It takes a 21 mm socket for front bolt side and I measured the back “0288” nut (that’s the last 4 digits of the part number) and it’s a 27 mm. I don’t have that size socket but a 1-1/16” wrench fits it well. 27mm=1.06299” and 1-1/16”=1.0625”. I have giant wrenches to work on my old Plymouth.

At this point, your diff is only still connected by the splines of the driveshaft. I next lowered the diff down some by easing the jack’s height down. I then started steadily pulling on the diff/trans jack combination and slowly it started showing splines. Eventually, it was free. See picture of diff on trans jack out in driveway.

You need to clean the external threading on the driveshaft. I used an old tooth brush and some WD-40. Whatever you think will get the majority of the old Loctite out of the threads. A new 50 mm nut, gasket, and retaining plastic clip is needed on the new diff. Note that the new nut has Loctite inside it as well.

The cup that the insert nut goes into on the diff needs to be cleaned out and re-greased. I used normal lithium grease. I asked dealer techs if there was anything special and was told normal grease was fine. The nut has an elliptical flange on it and it enters into the cup that is also slightly elliptical. Put seal on first, then insert nut’s flange, and then snap the clip over the seal. Also, the internal splines on the driveshaft need to be re-lubed with same grease. I added a small amount. You don’t fill up the internal spline cavity or won’t be able to push the diff and driveshaft together as the grease will be pressuring up and not allow the diff’s splines to fully seat. You’re lubing, not loading a canon.

I sort of learned as I went along and putting it back together was actually easier. I recall reading that I only had 5 minutes to get the driveshaft nut on and torqued back to 85 N-m (62.7 lb-ft). I took longer than 5 minutes and was fine. Torquing with a crow’s foot induces an error. You are using a longer lever arm than the torque wrench knows about. In my case, the torque wrench was 15” long from center of wrench to center of hand grip. Crow’s foot has an extra 2.25”.

Here is a link that explains it. http://www.engineersedge.com/manufac...e_wrench_1.htm
In my case, T=62.7 lb-ft, L=15, E=2.25, Y=(TxL)/(L=E)=(62.7x15)/(15+2.25)=54.52. For those that don’t want to mess with it, using my L and E values, the torque will be 15% high or 72.1 lb-ft. The point of the formula is I set the torque wrench at 54 lb-ft to get an actual of 62 lb-ft.

I stabbed the diff’s splines into the driveshaft, seated it as far as I could, and turned the nut a little bit (2 turns, approx) to get it engaged. I then jacked the diff up into position. I undid the ½ shaft belt supports and finagled the shafts into place. It was a little bit of a left and right push of the diff to get both shafts into the flanges. I then put the (2) 12 mm front bushing bolts in and threaded them in about ¾ the way up. I didn’t torque them but wanted to keep diff from twisting while I torqued the driveshaft nut as discussed above.

Next up was the rear bushing bolt. I stray from the OEM path here. If you have the standard cover, reuse your 14 mm bolt that is approx 112 mm long. I still think BMW spec’d it too short but it will obviously hold with the 33326770288 nut. I used an aftermarket bolt from Bell metric that is 140 mm long x 1.5 mm pitch. You need a hardened washer with it. I got a 14 mm washer from Bellmetric but a 9/16” hardened washer will work too. The Bellmetric bolt doesn’t have a flanged head like the OEM 112 mm long bolt does. Thus, the need for the washer under the bolt head.

The finned cover has a boss on it for the rear bushing. It is offset further forward that the OEM cover by a little more than 15 mm. This is where the aluminum spacer comes into play. The spacer goes between the back of cover’s boss and front of rear diff bushing. It took a bunch of fiddling around to get alignment here to be able to push the 14 mm bolt through. I got bolt through the bushing and slid the dog bone (p/n 33-17-6-773-193) back onto the bolt. Lastly, thread the new 0288 nut onto the 14 mm bolt. I went back and snugged up the (2) forward bushing bolts . Returning to rear bushing bolt, I torqued to 121.7 lb-ft (per list at top of this writeup). Specifically,I used a 1-1/16” socket and put this onto torque wrench. The bellmetric bolt has a 22 mm head on it (OEM has a 21 mm head). I braced front with a breaker bar and torqued on nut side as torque wrench wouldn’t fit not did I have good angle to apply 121 lb-ft to it. So, I cheated and torqued the nut side and not the bolt head side. Next torque the front bushing bolts to 73.8 lb-ft. I recall they use an 18mm socket.

Now angularly align each half shaft to its flange. I had car in neutral (with key on to be able to shift gear to N). I ran battery low doing this so I should have plugged in battery tender I suppose. I plugged it in after instead when I got low battery message. Use blue Loctite on new screws and make sure to use the arc shaped clip per 2 screws. Keep spinning the wheel to get a good angle to insert each pair of screws with clip. Here is where is good to have a helper with the e brake. Spin wheel to optimal access angle for torquing the half shaft screws and have helper apply e-brake. Then torque to 51.6 lb-ft. yell to helper for remove e-brake and repeat for all 12 screws.

Put all of the stuff back on that I covered in the “Get the stuff out of the way section”. I was lucky that I discovered that my compact spare was completely flat. The valve stem had gotten a leak and I would have been in a pickle had I needed the spare. NTB put new stem on and rebalanced for free.

[BB_cuda]

Here is where I learned about the use of the finned cover and what changes needed to happen.

http://www.1addicts.com/forums/showthread.php?t=1057536

[BB_cuda]

One last thing. I wanted to add a drain hole to either the cover or have a hole drilled and tapped into the bottom of diff itself. I feel the direct hole in diff method would more completely drain. Here is picture of a diff that has my style of finned cover and a rather large drain plug in bottom. I don't know what size that it is. I was wanting to pursue getting a 1/4" NPT put in but the thought came to me sort of late in the process.

Mentioning this so others can get this put into their diff work plan up front.

[TDIwyse]

Excellent writeup! Hope you enjoy your new mod :-)

[HP Autosport]

This has to be one of the most detailed final drive R&R I have ever read! It deserves to be a sticky on this forum.

[dmanb2b]

Originally Posted by HP Autosport

This has to be one of the most detailed final drive R&R I have ever read! It deserves to be a sticky on this forum.

PM sent to moderator

[Yozh]

Cuda, you may wish to add a disclosure that the finned cover may or may not fit with the factory exhaust, and may need trimming.

[BB_cuda]

Originally Posted by Yozh

Cuda, you may wish to add a disclosure that the finned cover may or may not fit with the factory exhaust, and may need trimming.

Yes sir. That is correct. Thanks Yozh. I will go put that up near top. The 1addicts thread I attached also says this. But of course, folks may not necessarily read that.

[BB_cuda]

My other diff shown in the pictures is headed west to same place that built my LSD. Another forum member bought it and had me direct ship it to Autotech. They are the manufacturer of Wavetrac. I snapped a couple pictures of the inside of it after removing fluid and cover. I even used the same Wavetrac shipping container. Some of you may ask "Why did I remove the cover?". The box and packaging is made for diff to fit without the cover.

EDIT: I need to be clear here. The shipment was done under the direction of the Wavetrac dealer who is doing business with Autotech. This dealer is working with forum member I sold unit to. Cautioning forum members that they can't just "up and ship to Autotech" without working deal with an authorized Wavetrac dealer.

[BB_cuda]

I have put 500 miles on new unit without issue. Time to test it beyond normal driving. I've been taking it easy in terms of wheel spins.

[Ohiodiesel]

Originally Posted by BB_cuda

I have put 500 miles on new unit without issue. Time to test it beyond normal driving. I've been taking it easy in terms of wheel spins.

Where on earth do you get this spacer?! I cannot find ANYTHING online this size. Through reading for the past 3 hours see that some other 1er's have made theirs or taken them to machine shops to be made..........

.....awesome write up btw.........

[BB_cuda]

Originally Posted by Rlemp

Where on earth do you get this spacer?! I cannot find ANYTHING online this size. Through reading for the past 3 hours see that some other 1er's have made theirs or taken them to machine shops to be made..........

.....awesome write up btw.........

I had a local machine shop turn it for me. After speaking with another forum member, I could have got it done for almost 1/3 the cost I paid ($75). I drew up the spacer by hand as it was very simple. I can privately ask the other member if he will make it for you. I'm pretty sure he will be migrating over to this same finned cover so it may be a matter of him turning an extra piece on his lathe.

On that other thread, I saw where a guy got a 1.25" diameter threaded SS piece and just punched the inside diameter out to 9/16" (0.563"). You are trying to have clearance for a 14 mm bolt to pass through. Some on the other 1addicts thread went with 14.5 mm (0.570").

I used to have access to a lathe at my old job and could have easily knocked this out during lunch.

[Diesel_Mike]

I'm an "aspiring amateur machinist" and this would be a really easy job. If you can't find a local source I could turn them out for anybody who wants one.

[Ohiodiesel]

Originally Posted by Diesel_Mike

I'm an "aspiring amateur machinist" and this would be a really easy job. If you can't find a local source I could turn them out for anybody who wants one.

Awesome, yes I for sure want one. I figure while I'm at it - I am going to replace and upgrade the Diff bushings as well. I see you can swap the front 2 bushings with the M3 spec ones but for the larger, carrier bushing - don't see anyone swapping for the beefier M3 unit. I researched the specifications and it looks like it will fit fine - it's also half the cost of original factory one for our 335D's so even if it doesn't work for some unknown reason, I'll just return it. For anyone interested in this see below for the part numbers....

Front M3 Spec. (2x required) - 33312284019
Rear M3 Spec. Carrier Bushing (In Subframe) - 33176770866

[Whitbread]

Ask and ye shall receive

[BB_cuda]

Way to go, Whitbread! Thanks for stepping up to support the 335D (and really the E90 328i, 335i guys too) community.

This spacer isn't specific to the 2.81 ratio diff. The folks with DCT transmission (E90 335is, 2.56 ratio) have the same 215 housing as we do and would use same spacer. I would have to go back to the 1addicts thread but guessing the smaller 188 diff case could use the same spacer. That is where i got the sizing specs from.

[Ohiodiesel]

Originally Posted by Whitbread

Ask and ye shall receive

Awesome

[Yozh]

Originally Posted by Whitbread

Ask and ye shall receive

How do we get one of those?

[OmahaDZL]

Im the lucky guy that is next up on the LSD train. I got Cuda's old one and its now being given the treatment with the new Wavetrac

Does anyone have experience with those M3 (or other) diff bushings?

Im tempted because, well.....bushings are kinda made to wear out and if Im there, why not upgrade?

Has anyone done this?

Thanks.

[BB_cuda]

Along with Omaha's question, this is the other aspect of supporting the differential and preventing wheel hop (if you have it). This is sold on another forum but here is the teaser picture. I will have to cut a notch into side of finned cover for this to fit BUT IT'S A DIRECT BOLT ON THE STANDARD COVER. You need to ask for the one to fit the large 215 diff.

I'm just amassing up parts for the eventual M3 conversion of my suspension. Likely this summer though. This kit is sold by VWetish over on n54tech.com.
http://www.n54tech.com/forums/showth...=38313&page=10

[BB_cuda]

Here is a shot of the clearance dimension of the finned cover. The angle of the picture is not quite right. The distance is 5". In addition, if the normal cover were on, the clearance to it would be 6". The VAC cover is a little bit lower but i don't have a dimension. I know that 335dFan has this cover. I will ask him for his clearance. His number may need a qualifier though as he had the M3 arms and stuff installed front and rear. His basis of comparison isn't standard 335D stance is my point.

[Yozh]

Nice photos. That finned cover looks great.