Joe Curry asks...
>I have just received a reply from Quaife to my request for information
>and their reply was very enlightening. Apparently they sell a
>differential without the Crown Gear and Pinion. They said that the
>Spitfire gears will fit into their differential unit.
>
>I'd like feedback from anybody familiar with the unit as to how
>difficult it is to install and change these gears.
Joe:
I've never added a Qauife unit, but have removed and replaced several
differentials and rebuilt one (these for the 1500 cc Midget, probably
not much different from the 1500 cc Spitfire).
Anyway, this job was pretty hard. I took the parts to a much more knowledgable
hobbyist (professional machinist background), and his very well equipped shop.
By way of background, I've rebuilt engines, reassembling them myself after
machine shop work; I've rebuild transmissions--these are much easier than
the differential repair I completed.
First, I would never have been able to even get the thing apart without the
many versatile fixtures he had for the various presses we used.
He also had some technical information which complemented what I had, allowing
us to get the job done.
The differential we rebuilt had a crushable sleeve, which we surmised served to
provide a controlled preload (the details are fuzzy in my recollection after
a couple of years). We could not get a replacement crushable sleeve, so we
"recalibrated" the old sleeve by plastically deforming it in the opposite
direction
with a large hammer. This made it slightly longer, allowing it to once again
crush at the right point in the tightening process. We could also have
shimmed, we
think, but we tried this, and it seems to have been successful.
I would never have been able to finish this job without the many different
gages he
came up with also. We needed to measure endplay, needed several mikes bigger
than I had, etc.
We had to fabricate shims from shimstock (this was not tough, but deciding what
thickness was needed was the challenging part.)
We had to rig a torque application device (a weight on a long breaker bar)
calibrated
to apply the prescribed torque to test the preload specification. I can't
recall exactly
what this tested, but we could not use a torque wrench for some reason (maybe
not sensitive
enough?)
Even with all this tooling and his expertise, we worked from early evening
until after
2:00 am one night just rebuilding the unit; it was a tough job. (We put it
back in
the car the next day with much less work.)
In short, this was probably a job for a pro, or at least a very knowledgable
and well-
equipped home machinist. Our unit is still working fine after a couple of
years in a car
that has the reputation of eating differentials (this is the third or fourth
since
we've owned the car). The cost of the parts makes it foolish to attempt it
without
significant resources like I've described.
To add the Quaife unit, you have to dismantle and rebuild to the same extent
that I've
described, I think. It just replaces the conventional carrier, I believe, with
the ring
gear bolting to the new part. Maybe it doesn't require the same sophisticated
procedures
for reassembly as the old unit, which would be the only reason I might
encourage you to
tackle it--you should ask the manufacturer for complete instructions for
installation and
review before deciding how to handle it. If you still have to deal with that
crushable
sleeve, it will be challenging. (get a new sleeve, if possible.)
If you can get a complete differential unit, properly set up by a pro, it is
not hard
to install it, but to rebuild differentials like the one we tackled is pretty
challenging.
Let me know how you like the Quaife unit.
Regards,
Ray
-------------------------------------
Ray W. James, P.E., Ph.D.
Texas Transportation Institute
Civil Engineering Department
Texas A&M University
College Station, TX 77843
Phone (409)845-7436; Fax (409)845-3410
E-mail: r-james@tamu.edu
Date: 12/10/98 Time: 5:38:26 PM
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