Swapping to a LSD from an open diff..... Complicated or straight forward?

ASO544 · #1 (**permalink**) 09-20-2015, 04:33 PM

How hard is this to do, mechanical wise? Once an LSD is sourced ( eBay or built) , is the actual mechanical part to swap it pretty straight forward or better to take to BMW or local mechanic. I have ok mechanical skills and swapped out Ford 9" before but the BMW is foreign ( &#128521

to me!!! Lol

Any suggestions or guidance will be greatly appreciated.

Grey 65 · #2 (**permalink**) 09-21-2015, 07:55 AM

Quote:

Originally Posted by ASO544

How hard is this to do, mechanical wise? Once an LSD is sourced ( eBay or built) , is the actual mechanical part to swap it pretty straight forward or better to take to BMW or local mechanic. I have ok mechanical skills and swapped out Ford 9" before but the BMW is foreign ( &#128521

to me!!! Lol

Any suggestions or guidance will be greatly appreciated.

Drain diff
Pull diff cover
Support diff
Disconnect diff
Remove diff

Reverse process

Make sure you used lactate on bolts when putting it back in.

I do it with my car on jack stands, but it would be much easier if done on a lift.

Kevin.....

cycleguy55 · #3 (**permalink**) 09-21-2015, 12:08 PM

Quote:

Originally Posted by ASO544

How hard is this to do, mechanical wise? Once an LSD is sourced ( eBay or built) , is the actual mechanical part to swap it pretty straight forward or better to take to BMW or local mechanic. I have ok mechanical skills and swapped out Ford 9" before but the BMW is foreign ( ��) to me!!! Lol

Any suggestions or guidance will be greatly appreciated.

If you're re-using your gear set and not touching the pinion gear, the biggest challenge is getting the correct lash when you install the new differential. Find the specs and use a dial indicator to ensure you get it right.

Edit: My experience is NOT with BMW differentials, obviously. I did some poking around yesterday and discovered BMW 'differentials' are sold complete. The closest description of something comparable for a Ford 9" rear end would include the differential assembly, ring & pinion gear set and the carrier / third member. When I changed my 'differential', all I had to do was buy the Torsen-type differential, transfer my ring gear from the old differential housing and install it in my carrier / third member. The differential unit was <$500, plus new bearings and the cost of having them pressed on.

Mark IV · #4 (**permalink**) 09-21-2015, 05:11 PM

Quote:

Originally Posted by Grey 65

Drain diff
Pull diff cover
Support diff
Disconnect diff
Remove diff

Reverse process

Make sure you used lactate on bolts when putting it back in.

I do it with my car on jack stands, but it would be much easier if done on a lift.

Kevin.....

What if you are lactate intolerant?

Mark Brye · #5 (**permalink**) 09-21-2015, 06:36 PM

When I swapped mine out, I noticed that the front mount bushing was bad. So I went to an aftermarket derlin bushing. It was not fun getting the stock bushing out or getting the new one in. I also upgraded to the larger front bolt which required drilling and taping.
I needed an extra set of hands to get the old diff out. Had to rotate it upside down as I remember. I also dropped the gas tank and unmounted the sway bar to get to the rear mounting points. When the diff is out is a good time to also install adjustable lower control arms.
I went with a 373 with 40% lockup. His seems to work good with the tall first gear of my tko600.

ASO544 · #6 (**permalink**) 09-21-2015, 08:09 PM

Lol.....nothing can be easy!!!! I'll probably find a lightly used one on eBay or have one built. Was hoping to just do the install myself but I've never worked on a BMW rear end or the bottom side of my Cobra. Peeking under there it's definitely cramped!!!!

I'm happy with my gear ratio but this thing needs a damn LSD......ASAP!!!!

Grey 65 · #7 (**permalink**) 09-22-2015, 07:39 AM

Quote:

Originally Posted by Mark IV

What if you are lactate intolerant?

Loctite... Sorry.... My iPhone thinks it knows what I meant to write.....

Kevin....

ASO544 · #8 (**permalink**) 09-30-2015, 04:08 PM

Can we remove the current open rear ends and have the rebuilt to LSD. Is there any difderence in the cases? What parts would be needed to accomplish this? Is it just the Clutch Type LSD Spool?

Grey 65 · #9 (**permalink**) 09-30-2015, 04:18 PM

Quote:

Originally Posted by ASO544

Can we remove the current open rear ends and have the rebuilt to LSD. Is there any difderence in the cases? What parts would be needed to accomplish this? Is it just the Clutch Type LSD Spool?

Yes you can reuse your carrier and gears if you want. You just need the posi unit and a rebuild kit....

Kevin....

ASO544 · #10 (**permalink**) 09-30-2015, 05:05 PM

Thanks... I may change my gears to a 3.64 or 3.73 from 3.46 while its out. Are our gears 168mm or 188mm? Also im guessing the rebuild kit are the seals and bearings?

Grey 65 · #11 (**permalink**) 09-30-2015, 05:44 PM

Quote:

Originally Posted by ASO544

Thanks... I may change my gears to a 3.64 or 3.73 from 3.46 while its out. Are our gears 168mm or 188mm? Also im guessing the rebuild kit are the seals and bearings?

188mm.... I had 3.46 in my open diff and have 3.46 in my 60% locked diff. What gear you use/need depends on the engine and trans you have. If I went to a 3.73 I wouldn't need first gear... With a 3.64 it would have been debatable if I would have used first gear.

Yes, since you have it all apart best to be safe and replace everything.

The oil you want to use is Amsoil 75w-140 severe gear oil. 3

http://bimmerdiffs.myshopify.com/col...products/188mm
Kevin

Kevin

ASO544 · #12 (**permalink**) 09-30-2015, 06:35 PM

I have a Roush 427R and TKO 600..... I'm turning 2000 rpms at 80 mph but it feels like it is almost lugging. I would prefer a little more rpms when running 70-80 in 5th gear.

ASO544 · #13 (**permalink**) 10-06-2015, 07:40 PM

I decided to just keep my current rearend and gears as they are new and less than 1k miles. I have plenty of local BMW mechanics for the work but is this the part i need and what is the exact difference? Which ones better.....

BMW E30 E23 E24 E28 E36 Clutch Type Limited Slip Differential LSD 188mm Spool | eBay

BMW E30 E23 E24 E28 E36 Clutch-type Limited Slip Differential LSD 188mm Spool

And......

OBX Helical Limited Slip Differential LSD BMW M3 E30 E36 Z3 6 Cyl Z3 M Roadster | eBay

OBX Helical Limited Slip Differential LSD BMW M3 E30 E36 Z3 6-cyl Z3 M Roadster

itstock · #14 (**permalink**) 10-07-2015, 05:55 AM

At a minimum, I was suggested Mfactory by the local guy for an aftermarket unit, with the preferred unit being OS Giken. I didn't even ask about OBX because all of the reviews that I had read stated they were complete junk. The used LSD wouldn't even be a consideration.

You are talking about $300-600 for what you are looking at, with the lower end being used and in unknown condition. The Mfactory is $900 for a brand new, warrantied for life helical.

It's the 188mm lsd unit, but I was told to get the one for the original gears/gears being used do to shims and what not (I don't know how true that is but I trust them as it's what they do). So you would want the E36 325 or 328 for your current open rear.

ASO544 · #15 (**permalink**) 10-12-2015, 05:08 AM

I emailed MFactory about their LSD spool advising them i was gonna install it in a BDR cobra with an E36 BMW rearend with 188mm diff. Their site advises the correct part number for an E36 (325 or 328) is

MF-TRS-05E36 BMW E36 ~1000whp $999.95 In Stock and Ready to Ship!
Description

Now they sent me this part number as the correct part for a 188mm Medium Spool

MF-TRS-05E46A BMW E39 ~1000whp $999.95 In Stock and Ready to Ship!
Description

That part number of course comes back to an E39, E46, E60. I emailed backand was again told thats the correct part numver for a 188mm Medium Spoolwith 3.46 gears

sort of confused as ido t wanna order the wrong part and find out when it torn open at the shop!!!!