Does anyone here understand the speedometer drive system?

OK, I'll admit to having speedometer problems since the day I got my car.

First it was the trip odometer, then after that was fixed, the drive cable broke.

I replaced the cable with a new 'generic' insert, keeping the cable housing that was on the car. They are the proper length, and the cable works, so that isn't my problem.

Since the transmission was changed to an automatic and the mechanic used the cable that fits the new trans, the top end of the cable that attaches to the gauge housing didn't fit right. Large nipple, small nut.

To remedy this I got a later gauge cluster that uses the small nipple, so now everything connects together nicely.

(Be patient, we're getting there...)

I disassembled both speedometers to try to get the odometer(s) in the new one to work right, and after I fixed it, the roller 'speed indicater' doesn't move when the car does.

The cable is fine, I checked it.

The magnetic drive disk is the right one for the nipple fitting - the small and large drives don't interchange drive disks because the shafts are different sizes. With the roller indicater removed, I can see the disk rotating as it should.

The roller indicator aren't interchangeable either, having different length center pins, so the roller I re-installed is the one that came with the new nipple and drive disk.

I installed the little retainer socket on the left side of the roller, and adjusted it so there is no slop in the roller. The tiny brass stop is set to hold the roller very lightly, at the firt revolution.

I can spin the roller with just the barest touch of my finger, but I must have overlooked some piece in the drive end. The dang thing still won't register any speed.

Back to the magnetic drive: I noticed that the roller itself is aluminum, but there is a steel insert (like a large washer) built into the right end and covered with aluminum. After trying several other things, I re-adjusted the magnetic disk so it is now as close to the steel surface as possible without touching.

Still no movement.

Is there a steel ring or something that fits into the recess on the magnetic drive end of the roller, or does the magnet just act upon the steel washer thing?

This situation is driving me nuts. I may end up buying a whole digital dash with the appropriate sending units, although I'd really prefer to keep the stock set up, especially after putting so many hours and $$ into fixing it up!

HELP!

Steve
barongrey(at)mchsi.com