RE: E28 Diff swap... and how to do it!

[Thi VanAusdal <tvanausdal@xxxxxxxxxxxxx>]

Uh, GGray suggests no shorter than 3.45:1 for the 'e' car.

... .... .. -   (who knows morse code here?)

I am transposing information here.

Diff swaps:
325is (3.73) to 533/535i (3.25) to 325e (2.91/2.79).

So, yes, since you have a '88 528e super eta, go with
the 3.25 or 3.45 (and I'm not sure, as I said below,
where to get the 3.45).  The 3.73 will be a shock.

People with a 2.79 (early 325e):
 Drive in 4th gear.  Do you like it?  That's what a
3.45:1 feels like in 5th gear!

> > I would rather have a quick car than a fast car, [it does 125
> > pretty easy] so what ratios should I look at? The ole' 
> > 4:11's? AND, can 'I'
> > do this? Or is it something that a 'trained professional' 
> > needs to do...
> > 
> > Oh, I have an 1988 528e 5 speed, 143hp?
> > 
> > >I did the swap from 3.25 to 3.73 on my '87 535is and love it.
> 
> The torque curve of the super eta motor will make highway driving a
> breeze with the 3.73; just point and squirt, as they say.  No more
> 4th gear downshifts!
> 

Boy, did I say a mouthful.  Yes, it will be QUICK in 5th gear.

Installation?

1. Pull flanges off the (I'll assume a 3.73 E30 diff) new diff.
2. Replace flange oil seals.   C'mon, they're cheap, and easy to get
   to RIGHT NOW.
3. Loosen the four nuts on the input flange of the differential on the
   car.  They are big, using a 17 or 19mm wrench.  Good luck, this may
   may be a tight space.  The driveshaft will move out of the way if
   you loosen the driveshaft center bearing nuts (8mm, use 13mm tool).
4. Remove the six 8mm socket head cap screws (allen bolts, okay?) on
   each halfshaft where it attaches to the flange on your diff in your 
   car.  The halfshafts are now free and will hang down.
5. Remove the speedometer wires from the sensor in the rear of the
   diff in car.  It snaps in, 2 wires, with a rubber boot over it.
6. Support the weight of the differential with a jack, blocks of wood,
   or tranny jack (I use lots of 4x4 pieces of wood! I'm jealous if
   you really have one!).  This is important unless you want your hand,
   chest, or skull to catch the diff for you.  I recommend against that.
7. Loosen the four bolts attaching diff in car to subframe.  Remove
after
   loosening all four.  SLOWLY lower the differential down and out of
car.
   Some maneuvering will be necessary to clear the subframe with the
nose
   of the differential.
8. Installation is the reverse of removal.  Check your oil level in new
   differential BEFORE driving vehicle, and recheck socket head cap
screws
   on halfshafts after 50 miles.  It is recommended you use new ones.
   Steve D'G, Phil Marx, Ron Stygar, or Michel Potheau may provide the
   appropriate part numbers.

One last note: Get a 10mm Allen key and attempt to remove the new diff's
fill plug BEFORE you install the unit.  If you strip it in place later,
you will not be happy!  They are notoriously tight but will come off 
with a good Allen socket on a long lever arm.   Notice I said Allen
socket.
I have had good success with a *socket* with an Allen bit in it - these
are
stronger than an Allen KEY, which has a right angle bend in it and can
vary
in quality more.  Yes, it can be THAT tight.

 - thi v.

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