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Go Back   E46Fanatics > Tuning & Tech > Driveline, Engine & DME Tuning

Driveline, Engine & DME Tuning
Talk about driveline improvements, NA tuning and DME tuning your E46 BMW here. This includes diffs, intakes, exhausts, chips, software and OBD tuning.

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Old 02-03-2012, 04:30 PM   #1
SoloII///M
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Fun with E46 Differentials: Gear swap

Preface

This is not intended to be a DIY. I've done a lot of work on cars over the years, but I am not a mechanic. I'm not that experienced with differentials. I do, however, like learning new things and had an opportunity. I'm not an expert. If you choose to use this as a guide, don't hold me responsible when you have to go crawling to Dan@Diffsonline to fix your stuff.

Purpose

I recently bought an E46 330Ci. This car was built several years ago by Bob Tunnell at BimmerHaus in Colorado. When they built it, they were limited to the gear sets that came in the 330, ZHP (both auto and manual). Off the top of my head, that's a 2.93, 3.07 and 3.38. Originally, Bob had Metric Mechanic build them a custom limited-slip differential for the car. The diff works great, but the 3.38 gears they chose are too short. Because the M54 can't rev like the iron block S52, S50 and S54, I need taller gears.

Rules have changed since then, and we can use any E46 non-M ratio. That adds the 3.15 and 3.23 to the options. After some research my co-driver and I decided a 3.23 out of a 325Xi 5-speed would be a good compromise. Dan@Diffsonline hooked me up with a set of gears and gave me a good price to set it up for me. Still, I wanted to give it a shot.

Tools needed
You'll need a few special tools for this (beyond sockets, wrenches, etc)

1) inch-pound dial-type torque wrench. Range 0-50 in-lb is desired. Mine is 0-75 which is fine as well
2) Two-jaw or three-jaw puller
3) Big-ass snap-ring pliers. Snap-on, Mac, Cornwell all sell these. Get a 16" set with .100-.120 straight or 15 degree tips
4) lb-ft torque wrench (click-type is OK here)
5) Hydraulic press
6) 30mm thin-wall socket (Sears or Gearwrench)
7) Dial indicator and magnetic base
8) Gear marking compound
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Old 02-03-2012, 04:31 PM   #2
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Disassembly

Here's where you start. Okay, you have to get the diff out of the car first, but bokchoys.com has a great write-up on that, so follow it.

Start by pulling the stub axles out. They just pull out, or you can use a pry bar.



Next, use your puller and a socket to pull the oil seals. You'll destroy them - that's ok. New ones are cheap. Repeat on the other side. You did drain the oil, right? If not, it's draining on your floor / table. Even if you did drain it, some will come out.



Next, you need to remove the snap rings holding the bearing races in, and providing preload to the diff unit. This is important and we'll discuss it later. To remove the snap rings, use your big-ass pliers. Don't try this with regular old wimpy pliers. Use a good set with a ratcheting mechanism, and wear eye protection just in case one lets go.



Here's what the shims look like. Note that this has a number printed on it. That's the thickness in millimeters (or should be. Measure!). Record what shim came from which side of the diff for later reference.



Badass snap ring pliers.



Now that you have the snap rings out, you can remove the bearing races. They might be a little stubborn, but no force should be required to get them out. At this point you can take the rear cover of the diff off and push them out with your fingers. (I don't have a pic of this, but it's just 8 bolts with a 16mm head. Easy.

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Old 02-03-2012, 04:31 PM   #3
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Now go ahead and remove the diff unit from the case and set it aside. It will slip out easily. You'll be left with the housing and the pinion gear, which is held in with a nut. Use an impact gun to take the 30mm head nut off the pinion. Once this is done, take the unit to your hydraulic press and press the pinion out. Once the pinion is out, remove the pinion seal from the housing.
You'll be left with this:



Note that the pinion still has its inside bearing on it. This is OK - you will be putting a new bearing on your new pinion (or using the one that came with it).

Now on the pinion there's a crush sleeve. The sleeve is used to set the pinion preload. You can get a new one from Dan@Diffsonline. I think it's 20 or 30 bucks. My advice? Get two. Just in case you screw up and overtorque your first one.



If you get your gears from Dan, he'll be happy to throw a new bearing on the pinion for you. It's still up to you to fit new outer races to your housing. Not hard if you have a bearing installer, but I don't have a pic of it.

Next, slide your new crush sleeve on the new pinion and put the pinion inside the housing. You will need to press the pinion in because the bearing on the outside of the case is a press fit (just like the one on the pinion). The easiest way to do this that I've found is to put the housing on your press so the press is acting on the face of the pinion. Then put an appropriately sized deep impact socket (I think I used a 30mm) under the pinion's outer bearing. Only press enough to get the bearing on! Don't go nuts and crush the sleeve. When you feel resistance, stop!



You'll be left with this:



Go ahead and slide the companion flange on. (Notice that I didn't put a new seal on yet!)



Go ahead and wind the nut on until it stops.

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Old 02-03-2012, 04:32 PM   #4
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At this point, you'll notice that the pinion is very loose. That is because the bearings need to be preloaded. You'll do this by winding down that nut gradually, until the correct preload is achieved. That little crush sleeve is getting crushed as you do this.

I made a special tool to hold the flange while I spun the nut. It's just a piece of angle iron drilled so I can bolt it to the flange. Mine is four feet long. Works fine. you'll also need a 1/2" drive ratchet and a piece of pipe or a jack handle. You need to be able to generate 300-400ft-lbs of torque to crush that sleeve.

Special tool:



Use your assisted ratchet and special tool and crank the nut down until the pinion is no longer loose. Now you need to go more slowly. Take the special tool off and use your inch-pounds torque wrench to check the ROLLING torque of the pinion. You want it to be 12 - 23 in-lbs. I shot for 12 with no seal installed.



Initially you'll probably have about zero. That's fine - repeat the process, turning the nut just a smidge each time. Go slowly and get a feel for how the torque ramps up with each twist. If you crush the sleeve too much you'll need to start over!

Once you're done, MARK the nut relative to the flange. Also mark the pinion shaft, so you can put the flange on in the same place.

Once you've done that, remove the nut, remove the flange (it'll just pop off - use a rubber hammer) and install a new pinion seal.



Install until it's flush. I used a 2 1/8" socket (rotary engine flywheel socket)

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Old 02-03-2012, 04:32 PM   #5
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Then put the flange on (again, exactly where it was) and spin the nut down (again, exactly where it was). Check the torque one last time - should be about 2-5 inch pounds greater (due to seal drag).

Success! Now flip the case over and install your LSD unit with new ring gear. Note I didn't take any pics of this, but it's very easy. Use an impact to get the ring gear bolts off. Discard them. Get new ones from the dealer. The ring gear will come off using a press or a few hits from a brass hammer.

The new ring gear gets heated to 230F (thoroughly - in an oven, not with a torch) and it will basically drop on. Use loctite red on each bolt and torque evenly to 110ft-lbs.

Here's your case with your LSD in it.



Flip the unit on its side so you can see one of the output shaft sides of the diff. Install the bearing race that came off that side. It will slip in.



Install the original shim that came out of this spot. IMPORTANT: This write-up assumes the diff was set up properly to begin with. If you swap bearings, LSD units, etc you need to set the rolling torque of the housing. I didn't swap any of that stuff so the only thing I need to be concerned with is BACKLASH.

We're going to start by using the shims that properly set up the previous gear set, just as a baseline. We'll probably have to adjust this (and in my case, this was true).

Here you're installing the original shim.



Make sure it fully snaps into the groove. Note that there's a huge gap between the shim and the bearing. That's because I've only done one side. When we put the shim on the other side it will preload the diff.



Repeat on the other side.

Now, check the backlash. There are plenty of pics online for how to set backlash, or you can read the E36 TIS. Backlash should be .003" to .004", with good gear mesh.

Now, here's why E46 diffs suck. BMW considers them "non servicable" meaning they don't sell the shims / snap rings! The only way to get more is to buy used diffs and scavenge. I have a pretty good selection, but I still didn't have what I needed.

My diff came with a 3.91 on the ring gear side and a 2.77 on the back of the ring gear side. That adds up to 6.68mm. That 6.68mm sets the PRELOAD of the diff. Unfortunately, with those shims my new gears had 0.0095" of backlash. Therefore, I need something smaller on the ring gear side and something equally thicker on the back side. Through trial and error I determined that I needed a 3.63 and a 3.05.

I have a 3.52 and a 3.66, which I'll just take to a machine shop and have them surface grind. Note that those two numbers add up to 6.68, meaning my preload doesn't change.

Unfortunately that's where I'm at for now. Once I get my shims ground I'll double check the backlash, gear wear pattern and button it back up.
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Old 02-03-2012, 06:57 PM   #6
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Very Awesome Write UP! Much more intense then American differentials.
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Old 02-03-2012, 07:03 PM   #7
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Quote:
Originally Posted by BimmerBrakes View Post
Very Awesome Write UP! Much more intense then American differentials.
Thanks.

Actually, it's about the same as a Ford 8.8. The thing that really sucks is not being able to buy those snap rings.
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Old 02-03-2012, 07:24 PM   #8
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Quote:
Originally Posted by SoloII///M View Post
Thanks.

Actually, it's about the same as a Ford 8.8. The thing that really sucks is not being able to buy those snap rings.
8.8 is much easier then this...

Edit: But yeah every similar...

Last edited by BimmerBrakes; 02-03-2012 at 07:36 PM.
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Old 02-03-2012, 07:41 PM   #9
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Smart man, nice tools Awesome write up! How many days did you smell like diff fluid after this Hate that smell!!! If it gets in your hair, you smell it for days.

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Old 02-03-2012, 08:17 PM   #10
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I got out unscathed but my garage reeks. I have four E46 diffs apart in there... not good.
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Old 02-04-2012, 04:41 PM   #11
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One thing I forgot to mention is pinion depth. Before torquing the pinion to achieve the correct preload, install the carrier and get the backlash as close as you can. Then mark the gears and check the engagement pattern. If it's not correct, you'll need to drive out the housing-side pinion bearing's outer race to get at the pinion depth shim.

In the case of my setup, even though I swapped the ring and pinion, the gear pattern was perfect, so I didn't need to change the shim. I did nab the shims out of my other diffs and lo and behold, they're all the same size. Odd, but I'll take it.

This thread has a great explanation of pinion depth, gear mesh and how to select the right shim:

http://forums.bimmerforums.com/forum....php?t=1650106
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Old 02-06-2012, 12:44 AM   #12
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I got out unscathed but my garage reeks. I have four E46 diffs apart in there... not good.
Lol, im complaining and i only have opened up two of them.
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Old 02-07-2012, 05:41 PM   #13
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great write up!

...sorry i never got back to you about the shims.
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Old 02-07-2012, 09:20 PM   #14
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A+ thread! Glad you're close! I'm looking to build a 3.23 LSD and will definitely hit you up for a job like this!...Just need the spare subframe to build the complete package and just do a complete plug and play swap to minimize downtime.
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Old 02-10-2012, 12:25 PM   #15
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You shouldn't need a spare subframe, unless you're doing something really exotic, it's a lot easier to swap the diff than the whole subframe. (ask me how I know!)
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Old 02-10-2012, 07:02 PM   #16
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What he said. No benefit to swapping the whole subframe. That's a lot more work.

After spending all the time doing this on my own I'm not sure I can recommend it. It has been a ton of work to get the gears set up properly.
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Old 02-11-2012, 12:54 PM   #17
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Spare subframe is for less downtime. I'm pressing in AKG bushings and diff mounts, plus RTABs. This is my DD, so the quicker I can have it on the road the better.

Literally only buying a spare frame, not the whole setup. I will swap all my stuff over when it's pulled, but the bushings take at least 2 days to pull when you don't have the proper tools LOL.

Thanks for the replies, fellas.
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Old 03-08-2012, 04:51 PM   #18
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awesome. thanks
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Old 05-28-2012, 08:54 AM   #19
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thanks for the write-up, and specifically the pictures. helped me with the break points for the input and output shafts.
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Old 06-15-2012, 10:03 PM   #20
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subbed - thanks
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