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RE: MG-TD Rear Axle Gear Ratio

To: mgs@autox.team.net
Subject: RE: MG-TD Rear Axle Gear Ratio
From: "A. B. Bonds" <ab@vuse.vanderbilt.edu>
Date: 25 Sep 1995 11:10:55 -0500
In <3066CEF5@msgate.reston.unisysgsg.com>, Unger, Larry @ RES wrote:

>Is the 'pumpkin' on the TD the same as on the A?  If so you could substitute 
>a
>used A/B pumpkin  (Moss Catalog Part #s for the A/B banjo rear parts are the
>same) ... you may have to change the wheel gears to match the axle splines.

Oh, nonnononono.  The TD rear end is yet another version of how not to
build a rear end.  It has neither a back plate (like the tube-type B
axles) nor a punkin' (chunk) like the banjo-type A and B axles.
Intead, it splits apart in a plane parallel to the driveshaft
(fore-and-aft), with the ring in one half and the pinion in the other
half.  The irony is that the ring and pinion from MGA's (among other
breeds) fit into this kludge.

> -> It's not a difficult conversion, but takes a lot of fiddly
> ->effort in setting the thing up correctly. I've been planning on doing this 
>
> ->for years, but have never found the occasion to take the car off the road.
> ->
>Thought that it took special tools to fit a new ring/pinion ....
>

In this case it takes a lot of machinist's blue.  You take a guess at
the pinion shimming on the basis of some calculations and paint the
ring and pinion surfaces.  Put the rear end together, work it a bit,
then take it apart and see where the blue is scraped off.  The contact
surfaces have to be made more or less symmetrical and centered (there
are a number of references showing what proper ring-and-pinion contact
is supposed to look like and how to get there).

I've got a lower-rear-end-ratio kit in my workshop but have not
installed it because I still don't have the patience for that kind of
fiddling.  Sound familiar?
                        A. B. Bonds


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