3.25 LSD is in!!

[larryn]

Okay, after sourcing parts from all over the country (including some last minute diff output flanges form a e30 being parted semi-locally), I now can do 2 wheeled burnouts. :)

I replaced the 3.45 open diff with:
3.25 diff from a 1989 535is in San Diego w/45000 miles (it looked new)
diff cover from a 1988 325i in S Carolina
e30 half shafts from a 1990 325is north of Boston
e30 differential output shafts from a car being parted west of Boston

Install wasn't a snap, but it wasn't that bad either. The hardest part was aligning the diff mounting bolts, but it really helps to catch the drive shaft bolts, catch one diff mounting bolt, then jack the diff up at various angles to catch the rest of them. I figure I put about 8 hours into it, but I replaced the shocks and springs too.

All I can say is WOW. I used to be at 4000rpm @ 80mph on the highway in 5th gear. I shaved nearly 1000 rpm from that. Driving around town is no longer a 4th gear experience anymore. With the S52, first gear was a mere blink. Now I can ride it out a bit more.

There are no grinds, bumps, whirs. It is silent. I was so pumped I detailed it afterwards.

Tomorrow I test it at autocross! http://www.e90post.com/forums/images/smilies/burnrubber.gif

[PeteN95]

Sounds sweet and such an appropriate smillie!

[windnsea00]

What tranny is in your car...the Ti Getrag unit or the ZF M3/328i one or something else?

[larryn]

I have the M3 tranny.

I got put in a pretty steep class at autocross (highly modified M3s), obviously, but I did okay. I loved being able to power through entire slaloms with no inside rear spinning. I could rotate the car easily too. I had a blast.
http://jabber.tardcat.com/photos/photos.cgi?cache=yes&album=irc&res=1024&image=1182262753.jpg

[windnsea00]

I was wondering, you said it was at 4k rpms at 80mph? Because in the Ti with the standard tranny and 3.45 it's at 3.8k rpms at 80mph so is 5th gear actually lower in the ZF unit?

[larryn]

I think they both have a 1:1 final gear in the tranny. There is no overdrive. Maybe I was going 82mph or so to see the indicated 4k rpm?

[windnsea00]

I think they both have a 1:1 final gear in the tranny. There is no overdrive. Maybe I was going 82mph or so to see the indicated 4k rpm?
Ah ok, well if I do the swap in the near future I will ditch the idea of a cheap 3.73 from an E30 lol.

[DustenT]

Install wasn't a snap, but it wasn't that bad either. The hardest part was aligning the diff mounting bolts, but it really helps to catch the drive shaft bolts, catch one diff mounting bolt, then jack the diff up at various angles to catch the rest of them. I figure I put about 8 hours into it, but I replaced the shocks and springs too.

Larry -

Looking for tips here. I have the drive shaft bolts installed, and the two front "ears" bolts in, but the top 2 bolts are driving me NUTS. I tried loosening the ears and the diff mount to give it some wiggle room but it's not moving much. Do you remember where you put the jack to get the top 2 bolts in? Did you leave the two ear bolts tight the whole time. I did this once before when I installed the 3.45, but that thing was a little easier to move around.

Thanks man!
Dusten

EDIT: I Just read Panzer's suggestions, I'm going to go try this now. Man I want to drive it tonight!!!

Note Installing the Diff

Aligning it on the Subframe can be a pain in the arse. Do the ear bolt(On the diff cover last) and it is a tight fit, but it fits.

of the bolt bolt design

0---0
0-0 <---try to align and start these first(Top bolts of the diff), if you can't get them, pass on to the fronts which you can see, but the major trick is to bolt all 4 down at the same time alittle at the time. Then before they are completely taught do the ear bolt while you can still move the diff around.

[DustenT]

Ok, got it in. Here is the trick, I'll modify Panzer's info

Installing and Aligning the Diff

Aligning it on the Subframe can be a pain in the arse.

Do the ear bolts last.

Bolt Design

Front
0---0
0-0
Rear

Align the top (rear) bolts first. It's almost impossible to do this with a jack, you'll need to freehand it with a helper (thankfully I'm a big guy, did it myself :) ). Once you get one started, don't tighten it all the way, get the other one started. Only tighten them enough to hold them in there. Now move to the front, there should be enough play to move the diff around to get the front bolts lines up. Only tighten the front ones down a little bit too. Now move to the rear and insert the diff mount, you'll probably have to jack up the diff to get this one in. Tighten the diff mount bolt all the way down. Now tighten the other 4 bolts down, little by little so they snug up at the same time, otherwise it'll bind (not good).

Oh yeah, if you get to this point and realize that you can't get the axles in, don't panic. Disconnect the strut and let the trailing arm drop down, this will give you enough room to get the axles lines up. Yeah....I did that. :)


My line on e30 axles fell through so I just used the 318ti flanges and axles. While up in the air there was a little grinding noise, but once on the ground it worked great. I'm guessing that while in the air the axles sag out enough to cause a problem, but now while on the ground. The gas in the car is like 3 months old now, so tomorrow I'll get some new gas and really test it out. Still looking for a good deal on e30 axles. I anyone has some, PM me.

Hope this saves someone some frustration!!!!!!

[larryn]

Sorry I didn't see this sooner, Dusten. I had problems too, and just caught one bolt slightly, and then tried to align the other bolts. Sounds like you did the same thing.

At one point, I was almost positive that the there was no way I could get all 4 bolts installed, adn it was a different bolt configuration.

Congrats though!! Since you didn't replace the half shafts yet the grinding couldn't have been the ABS sensor, so keep an ear out for funky noises. Having a locking diff made a world of difference in the car though. You'll see. :D

[DustenT]

Having a locking diff made a world of difference in the car though. You'll see. :D

Yep I know, I had a small case diff in there before. When I did my transmission swap years ago I put in a club sport LSD, much better than the open diff!!

Going to give the car a good beat down today, the rear end feels VERY nice with the new subframe bushings and trailing arm bushings, feels like brand new!

[zboot]

Sorry, I didn't see this till today. For me, I did the ear bolt in, didn't tighten it, then got the two top, then two bottom. Just enough to get the threads started. Once those four were in, and aligned properly, I tightened them down. In order to get the alignment right, I needed to push/pull the diff from side to side while a friend threaded the last two in place.