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Differential Rebuild - to do or not to do

To: <6pack@autox.team.net>
Subject: Differential Rebuild - to do or not to do
From: "Michael Corbitt" <michael_corbitt@ous.edu>
Date: Mon, 31 May 2004 11:46:32 -0700
I bought my 69 TR6 late last summer and am now in the process of going through 
all the components in the rear end to make sure it is road ready for driving 
more than a few miles away from home.  This weekend a fellow TR6 enthusiast 
drilled and tapped my differential housing for a drain plug.  While having the 
cover off I inspected the internals and found a tooth broken from each of the 
10 teeth pinion gears in the differential carrier, and a small chip (eighth 
inch) in the outside of a ring gear tooth.  Not exactly what I wanted to see, 
but something to expect from a 35-year-old car.  The 2 teeth were in the bottom 
of the differential in what appeared to be about a half pint of gear lube.  

Money is an issue.  I don't have a $1000 to spend on a rebuilt unit, and the 
risk of getting a used differential with similar problems feels too great to 
buy one off the web. So I'm considering rebuilding the differential myself 
following the Haynes manual.  I have both Bentley and Haynes manuals, however 
the Haynes seems to provide more thorough descriptions of the steps to take.  
It looks a bit overwhelming, but I'm pretty good at following instructions, and 
I take lots of notes and pictures to document what I'm doing.  

I looked at my collection of archives on this subject but didn't really find 
much regarding the process of doing a rebuild in one's garage.  I do plan to 
check with a local transmission shop to get their opinion on everything, but I 
wanted to tap the collective wisdom of the list serve to get your opinions, of 
which I value more.  

I have a few questions I would like to ask.  

Am I crazy to think that I can rebuild this unit, and have a comfort level to 
drive it more than a few miles from home?

Should I just call my banker and buy a rebuilt?

Should I leave it up to a local transmission shop - I hear there is a fairly 
reputable one close by?

If rebuilding myself, should I replace the ring gear because of the small chip 
in the tooth?  TRF wants $300+ for the ring and pinion set. Ouch.

Is it a big gamble to just replace the 10 teeth pinion gears in the carrier and 
all the seals (assuming the bearing look and sound okay), or should the 
bearings be replaced while I have it opened up (since they're probably the 
originals)?

The Haynes manual indicates that the average garage does not have the special 
tools to enable a very accurate mesh of the crownwheel to the pinion and thus 
ensure that noise is kept to a minimum.  It says if you can't tolerate the 
additional noise, go to a Triumph garage.  Is noise the only issue?  Won't a 
less-than-accurate mesh of these gears cause them to wear prematurely?

When I took the cover off, there didn't appear to be a gasket.  It was more 
like there was a thin film for a gasket.  I didn't have any leaks, but this 
seemed a little unusual to me.  Is this how it comes from the factory?

Any and all opinions and additional information to help me make the a good 
decision would be appreciated.

Mike
Corvallis, OR





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