If you have trouble with the Differential nut, readme for ideas

[Aaron]

I just finished putting an LSD in my 44,000 mile 335is. Overall went pretty smoothly, but you guys have no idea how much toruble the diff nut caused me. I borred a 50mm fan clutch wrench from an N5X guy who had used it on his car. When laying beside the car using my foot to kick it/apply stead pressure, the wrench bent around the nut.

I had a 48mm wrench that's about double the width of the fan clutch wrench, so I milled it out to 50. It was too loose, I milled a hair too far. And the nut actually dug into the flats on the wrench.

I was at a loss. Nothing I did could break this damn thing loose. I tried the butane torch on it, tried using my legs, using both arms while bracing myself against the car, NOTHING.

I bought a 50mm wrench from Harbor Freight, and it held the nut closest out of the 3, and was also the widest, and the longest wrench. To my surprise it fit, albeit it barely, without any grinding. With 2ft of leverage I still could not get that nut to budge. Then I had an idea.

You all have no idea the amount of torque I put on this wrench before that nut budged. I was easily over 1,000 lb-ft. I had to crank on that ratchet strap.

 

[doublespaces]

My question is, how did you lift the diff up into place? Did you have a tranny jack or something? That SOB is heavy

 

[Aaron]

I used a floor jack, just balanced it on the floor jack, and lifted while another person gets it lined up and the bolts started. It didn't really give us much of an issue, but ya, it's not light.

 

[Bmwfixerguy1]

You gotta heat the nut bud. They have a loctite type agent that is insanely strong and has a lot of surface area to bond too.

Even with the BMW tool that has a collar that goes over the open end with locking pins to make it a closed 50mm and a telescoping handle it still takes three of the biggest guys in the shop to bear hug it in a big 70s gay porn looking kinda scene!!

 

[Aaron]

I tried the butane torch on it,

I tried heat!

But it's nice to know I'm not the only one who has issues with it, I was concerned when every post I read didn't say much about the big gay porn it took to get it off!

 

[Aaron]

On a side note, drove it today. Now this is a used unit, but has very low miles. It turns great, accelerates good, and overall seems good.

My only issue is a whine when decelerating. Completely off the throttle, between 30-60mph, it whines while it slows down. Not a loud whine, but enough to notice. Anyone know if this is normal or not? MFactory 3.08.

 

[Bmwfixerguy1]

I've never driven one with an lsd..

Bump for your answer

 

[doublespaces]

I'm auto with the 3.46 mfactory 'big' (215mm) differential. I've never noticed any whine at all. Completely silent as far as I'm concenred, and this was built by syncrotech themsleves, with new bearings.

 

[dyezak]

Shouldn't be whine...

And I used a 4' long cheater bar last time I did that. I still had to tug quite a bit, but it worked.

 

[Aaron]

The whine is more accurately described as a howl, but only occurred on decel/coasting. Extensive Googling showed this situation is consistent with low preload, so in my case either an incorrect assembly or a loose pinion nut. The unit was assembled by Jordan with RK Tunes, a specialty shop that shouldn't have a problem doing so (Especially since the pumpkin is identical in design to every other pumpkin ever). So that leaves me with a loose pinion nut. How TF?

I had a friend help me with install. The friend decided he didn't want to tighten the diff nut manually, since it takes all day turning the wrench one increment at a time. So he convinced me to put the wrench on, lock it against the body of the car, turn the motor on, and "drive" the car on jackstands to tighten the nut for us. This worked incredibly well, fast too!

Well at some point in this adventure the diff nut got too tight. We didn't know this, and kept going. The diff nut got too tight, pulling too hard against the pinion nut. Eventually the diff nut locked itself to the pinion nut, so with each turn tightening the diff nut, the pinion nut loosened a turn.

As I was tearing it back apart, loosening the diff nut would move the pinion nut, tightening that. Bad sign. The problem now is how does one set prelod? The pinion nut doesn't have a torque spec, it's torqued to proper preload. Well I can't set prelod with the diff in, and I wasn't about to disassemble it.

BMW will not loan out the pinion nut tool, and there wasn't another in this city. It's a 12 point, about 65mm. A 2.5" wrench from Harbor Freight is a tight fit, but works well. The 2.5" socket from HF is too tight, it won't fit, and the 2 5/8" socket will work, but it's very loose. I decided to tighten the pinion nut until the unit turned with the same amount of force as the OEM pumpkin, which luckily I still had with me.

This was a pain in the ass, but it's the right way to do it. In order to tighten pinion nut, I had to connect the half shafts. To test preload against the bench OEM unit, I had to disconnect half shafts. So tighten nut a hair, remove axles, test force and compare to OEM, and redo. Took me about 6 times before I got it perfect. Reassembled and took the car for a drive, diff is silent!

 

[dyezak]

Jesus man...what a mess. Glad it's back to normal though!