E30 Diff. Swap/Speedo Sender Question

[Scott Ruffner <jpr9c@xxxxxxxxxxxxxxx>]

So I just completed a differential swap on my '86 325e.  Wow, what a
difference!  The old diff was an open 2.93, which was pretty shot -
moreso than I realized.  It was noisy, but I hadn't realized how much of
the take-off shuddering an jerkiness was the result of the differential
not turning freely or binding up.

I got a 3.25lsd from an '87 535i in the junkyard, replaced all the seals,
and used the rear cover from the original.  The smoothness of the takeoffs
and the extra bit of zip is just awesome.  The highway revs seem to be
just fine, although I can't say for certain quite yet, since I don't have
a speedo now, which brings me to my current question:

Are there differences in the pickups?  I just left the old pickup on the
old rear cover - I believe it was working just fine.  I'm not positive,
since the speedo itself quit several months ago, but I believe that was
just the result of a solder joint/trace on the back of the display cluster
failing.   The reasons I believe the pickup was working are:

1. The cruise control still worked.

2. The "econometer" still worked.

Since the swap, I haven't tested the cruise, but the econometer is pegged
on either 0mpg (engine under load), or 40+mpg (engine under braking) - I
suspect it's not getting a signal from the sender any longer.  I've
double-ckecked the connector, and it's firmly seated.  Same sender as was
working earlier in the day.  Is there an incompatibility with the 5 series
senders and the 3 series?  They looked physically identical.

There was a layer of metalic sludge attracted to the magnet on it (from
the old diff eating itself), and I cleaned that off, but I can't imagine
that did it.  Is there a simple test?


Scott



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Scott Ruffner
Computer Systems Senior Engineer       Computer Science Department
ruffner@domain.elided                University of Virginia
(434)982-2219                    http://www.cs.virginia.edu/~jpr9c

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