[Fot] Spitfire MKIV Diff

[Scott Janzen]

Hi, Shawn:
 Have done this on my GT6 and yours will be similar.
If you are just replacing the output stub shaft bearings and seals, you don't
need any special tools.  On the GT6, you can disconnect the halfshafts and
pull the stub s with the diff in the car, though its certainly easier on the
bench.

Noises - I like to do things once, so I would pull the whole unit out and
figure out where the noise is coming from - it may be the pinion bearings, the
stub shaft bearings or likely the ring and pinion gears.

If your pinion seal is leaking, replacing it is a project.  I think you need
to pull the diff and totally disassemble it, though if someone has a shortcut
I'm all ears.  I've never been able to pry one out from the front with the
pinion shaft in place, so the following instructions apply to total
disassembly.
You need a factory manual for instructions and tolerances, but it is easy to
follow.
You will need a dial indicator, a micrometer (to measure shim thicknesses
accurately), a good torque wrench, and I suggest a differential housing
spreader.  The last item is because the differential carrier with bearings is
several thousandths of an inch wider than the housing (3/1000 on a TR4) to put
a pre-load on the bearings.
I asked questions about removing the differential carrier recently for the TR4
- some said I could remove the carrier without a spreader - you might want to
read those emails about two weeks ago - but I found it easy to make one out of
two pieces of 2" angle iron and some 5/8" all-thread rod and the same thing
will work for a Spit diff.

If you do have to make adjustments to the shims/re-load, etc, the spreader
makes things much easier.

Have fun - it's pretty simple in there!

Scott

On Oct 4, 2013, at 4:03 PM, Shawn Frank wrote:

After the 1000 miles on the Spitfire to and from Road America for the Kastner
Cup, my differential started making some noises and leaking more than I would
like. It did get my wife and I back home safely with no problems other than
that. We even got cheese! A success in my book. This rebuild will be the very
last thing I need to rebuild to make this a completed restoration. Not
completely done, just completed (for now).

I have purchased all the bearings
and seals to refurbish this 42 year old diff (Spitfire MKIV), but have never
dug into a differential of any kind before. Do I need a special tool or two?
Can I get to the inner and outer carrier bearings and output shafts without
taking the gear assembly out?

I am missing a Rally Cross and an Auto Cross
event and it is killing me! I still haven't track tested my new suspension,
aside from touring laps and parade lap on the 4 miles of black magic that is
Road America (Joe Alexander). Any advice or help would be greatly
appreciated.
I plan to look in a Kastner Prep handbook tonight and a couple other repair
manuals, but the workshop manual (Haynes or Chiltons, I can't recall) says
that someone qualified should disassemble. Who listens to that?! I hope to
get
to it tomorrow...

Shawn Frank
Spitfire & GT6 Magazine
Continued Legacy
Friends of Triumph/NASS#746/BCCI

71 Triumph Spitfire MKIV
80 Triumph
Spitfire 1500
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