Hi,
Rebuilding a differential is quite easy with normal shop tools. I can
provide exact details if you need them.
The "play" you refer to with your differential is called "backlash" or
sometimes "freeplay" and it can be tightened up by playing with shims. Our
club (New England Triumphs) just did this operation for a member. We had
to take the unit completely down and then figure out what shims we needed
- we ordered them and then waited, but eventually got everything to put it
back together.
To figure out what parts you need, you have to take the center section out
of the differential. Contrary to the manual, you do not need a case
spreader. The center section is an "interference fit" (+.003, I think), so
with a soft drift and a hammer you can rock the pumkin out of the case.
I've done this many times. But once you get the pumpkin out, your backlash
_could_ be from the thrust washers to the "sun gears" and/or the "planet
gears". The sun gears all use fiber washers, old units have brass... The
planet gears have precise-sized brass "cups". If either of these thrust
washers is worn or missing, you will get a lot of freeplay. The cup
washers are marked with the size (e.g. 56) which is the size of the thrust
washer in "thousandths", (e.g. .056"). The new cups are in size ranges, so
the "56" replacement is the one labelled ".055/.057".
Now - if the unit was noisey, then you probably need to check the
bearings, particularly the pinion head bearing. If you determine that this
need to be replaced and you are not a really competent mechanic, you would
be best served by having a professional take over with the overhaul.
Replacing the pinion head bearing is easy, but once it's replaced, you
have to set the pinion head height - and this requires either a special
tool or real patience and determination (as you will never get it right by
guessing and you have to completely assemble/disassemble the unit to
change the height).
Regarding your leaky seals, the pinion seal is easy to replace, but you
need to be aware that some TR6's used a collapsible steel sleeve to set
the bearing preload on the two pinion shaft bearings. If you overtighten
the pinion flange nut on one of these diffs, you will change the bearing
preload and you will likely smoke a bearing soon after doing the job.
Unfortunately, there is no way to ID whether you have the old style or the
new style (pinion bearing preload adjustment) by visual inspection. The
early style diffs used a slotted nut and cotter pin and the later style
used a nyloc nut, but over the years it is very likely that the seal has
been replaced and that the nut was replaced with the "other" style.
That said - if you have time and patience, you can do this job, but you
need to be aware up front that there are operations that require lots of
"fussing" and if you get into changing bearings etc, then you need to
consider getting lots of shims so you can set pre-load, side-to-side
clearance, pinion head height etc. All these dimensions are _critical_, so
you must get them "right". The job is doable, but it really weighs out as
a job that is "advanced" as opposed to "intermediate" or "novice" in terms
of mechanical aptitude.
The three-month turnaround sounds a bit long, but I'll bet TRF uses that
to set expectations as opposed to how long the job will actually take. On
the other hand, rebuild shops get the most busy just before the driving
season and extending into the driving season because _everybody_ waits
'till the last minute to do this sort of work on the car. Ask me - I'm an
expert on it! I still have 20 or 30 small projects including a complete
brake overhaul on my "driver"!
Regards,
rml
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