DIY: How To Swap a Differential (plenty of pics)

**clumpymold** · 10-26-2005, 04:16 PM

Originally Posted by hellrot325

I posted the proper spec's above. And they are not stretch bolts, they can be reused. Way earller in this thread I indicated where to position them for easier access.

So which is it? Are they M8 or M10?

**ccblanket** · 10-28-2005, 05:39 PM

I guess M10, take a look at :
http://www.realoem.com/bmw/showparts...68&hg=33&fg=25

**ccblanket** · 10-30-2005, 02:45 AM

I did the swap tonight, and only thing left id putting in the fluid. How many qts diff fluid should I buy?

**leedawg** · 10-30-2005, 02:52 AM

2 qts takes 1.8

**M52 POWER!** · 10-30-2005, 03:14 AM

.2 goes on the ground

**ccblanket** · 10-30-2005, 10:46 PM

ok, filled in w/ the fluid and test drove the car. Either my prev diff was a 3.46 as well, or it will get better after the break-in period. I didn't feel a huge difference (at least for the 1st gear). I am scared to push the car before break-in.

frankly, how do you know if a diff is 3.15 or 3.46 or whatever?

**Tommy R** · 10-30-2005, 10:57 PM

Jack it up. Count the number of driveshaft revolutions per one wheel revoltion. Also, you could check your rpm at a certain speed in a certain gear. A 3:15 ratio in a BMW with a 1:1 high gear turns right around 3000 rpm at 70 mph.

Tommy

**clumpymold** · 10-31-2005, 07:25 AM

Originally Posted by ccblanket

ok, filled in w/ the fluid and test drove the car. Either my prev diff was a 3.46 as well, or it will get better after the break-in period. I didn't feel a huge difference (at least for the 1st gear). I am scared to push the car before break-in.

frankly, how do you know if a diff is 3.15 or 3.46 or whatever?

Where did you get the 14mm allen socket? I bought one off eBay but I noticed it's too long to even fit in that small space (let alone get a ratchet in there). I really don't want to take my differential out to add more fluid. Any suggestions?

**Tommy R** · 10-31-2005, 08:30 AM

Autozone sells a three pack of these allen sockets and they're made for a 1/2" ratchet. Put the socket in a vise and punch out the allen key portion of the socket. It takes very little effort. Insert it into the drain/fill plug and use a wrench to turn it. Very easy.

Another option is to get a 14mm allen ley and cut it to taste.

Tommy

**ccblanket** · 10-31-2005, 10:52 AM

another option is -what I did- buy it at zdmak.com

They sent me a FACOM brand socket (3/8 drive), and it fitted perfectly. (They ship pretty fast as well)

-h

**clumpymold** · 10-31-2005, 05:05 PM

Originally Posted by Tommy R

Autozone sells a three pack of these allen sockets and they're made for a 1/2" ratchet. Put the socket in a vise and punch out the allen key portion of the socket. It takes very little effort. Insert it into the drain/fill plug and use a wrench to turn it. Very easy.

Another option is to get a 14mm allen ley and cut it to taste.

Tommy

I'll try taking that piece out. Or maybe cut the tool to fit? Is that going to be too hard?

ccblanket: Wow, they're pretty expensive. $20 unshipped. I paid $14 shipped for my one. And I'd prefer to not spend any more money. Besides, those look just as long as mine.

Oh, what's interesting is that, on the 10mm and 14mm page link, the two tools are identical. They just resized one to make it look larger. That's pretty shady instead of taking actual pictures of the item.

**ccblanket** · 10-31-2005, 05:18 PM

it's a bit pricey. I paid a lot for all the little tools etc to do the swap. I was wondering if I should have spent more and get it done at a shop to save my arms and chest from the pain of lifting that heavy block up.

I think the cheapest (low quality) part of all I bought for this thing was the fluid pumps. I bought two, one of them didn't pump anything at all, and the other one was leaking from top or bottom. What a lousy workmanship.

**5speed300** · 11-23-2005, 11:42 AM

Bumping this because I'm doign the swap in 2 days. Can anyone tell me if I am missing a lockring or washer or something on output flanges? Heres a pic of the diff I am installing, it didnt come with the m3 output flanges becuase they wouldnt fit my 325 anyways. So does it look like anything mising from this pic?

**Tommy R** · 11-23-2005, 01:08 PM

Yes, you're missing the diff output flanges. You should be able to pop the ones out of the current diff and put them in.

Tommy

**leedawg** · 11-23-2005, 01:18 PM

It should look like this. See how your missing the output flange all together. But luckfully you can just use the ones off your old diff so your in luck.

**Jeffrie** · 11-23-2005, 02:28 PM

Your ok they just press in & out no lock washer.

**5speed300** · 11-23-2005, 04:24 PM

Ok great thanks guys. I know I was missing the output flanges themselves, just wanted to make sure there was nothing in between that I didnt have. Thanks alot!

**Spahrman5** · 11-23-2005, 04:30 PM

I bookmarked your thread a while back and just did the swap today. Very good write up, thanks

**Tommy R** · 11-24-2005, 11:24 AM

Originally Posted by Spahrman5

I bookmarked your thread a while back and just did the swap today. Very good write up, thanks

Glad it helped.

Tommy

**5speed300** · 11-26-2005, 11:14 AM

Well I just did the swap last night and took the car out for a drive and am incredibly pleased. I do notice 1 thing though. When I take really sharp turns at low speeds the diff seems to make a very low hum sound. Is this normal? The differential is a 3.23 with 55k miles on it so I dont think its going bad, I hope not anyway. Its running some heavy duty shockproof oil right now and I think that switching over to some redline may help smooth it out a little. The diff was also sitting for about 4 months without being used and my garage gets pretty cold, maybe it just needs to be driven a bit? Thanks

**leedawg** · 11-26-2005, 01:57 PM

You dident put new oil in before you installed it? Why not ? Change the oil put some new oil in and put the addative in for positraction rear ends. Or get the redline that is made for the posi rear ends.

**5speed300** · 11-26-2005, 02:01 PM

I didnt change it becuase the guy I bought it from changed it right before he sold it to me. He also opened it up and tightened everything back down to spec. I need to change the tranny and engine oil anyway so I'm probably just gonna put some new redline in the diff at the same time.

**leedawg** · 11-26-2005, 02:06 PM

Um well sounds good to me. I dont trust anybodys work except for mine. Id change that oil asap. ITs cheap and is peace of mind knowing that its done right .

**Tommy R** · 11-26-2005, 03:52 PM

I don't know why he'd put a shockproof oil in there since it's a clutch pack diff. Of course, I'm assuming it's the OEM diff. I use Redline 75W90 NS. Yes, the diff may occasionally make a moaning noise when making tight turns. That's not very uncommon.

Tommy

**5speed300** · 11-26-2005, 03:59 PM

Great thanks for the help!

Thread: DIY: How To Swap a Differential (plenty of pics)

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