Half Shaft Replacement
Among the most frustrating of the Tcar's
catastrophic failures occurs when when the clutch is released and
the car doesn't move, even though you know it's in gear! Ah yes!
the infamous half shaft breakage. One can't really be surprised at
this happening. The original half shafts are at least 50 years old
and have had an awful lot of twists applied through them. It
doesn't seem to be the case that the half shaft will decide to give
up the ghost as you begin to back your car out of your garage.
Instead, the is some gremlin whose job it is to assure the said half
shaft will break at a most inopportune moment and location. We then
find ourselves in three situations -- Case One, where we can very
simply pull the car into our garage and proceed to begin the
replacement process; Case Two, where we can have the car delivered
to a competent shop so that they can begin the process; and Case
Three, where the job has to be done in situ. In this section I'll
try to see if I can't give some help and information to cover all
three of these cases.
Common to the entire thread is the presence of a
useable replacement half shaft. This is an area in which it's
worthwhile giving some serious forethought. New half shafts are
available through the usual suppliers of parts for our cars (bless
them), e.g., Abingdon Spares and Moss Motors. IMHO, the best bet
out there now are axles developed by the late Jerry Austin and
continued by Dave Clark. They are of top quality design and
material and are now available from Tom Lange at very reasonable prices.
Tom can be contacted by
clicking here on his name
Tom Lange.
Information about the axles:
********
The material and hardness
specifications for you metallurgists out there are as follows:
Old Material: 1340 New material: 1541.
Heat treating is by high-temperature induction.
The shaft was originally surface-hardened to #50 ~ #55, whereas it
is now done to #62 (which penetrates further--to about 1/3 of the
diameter).
Also, the shaft itself, where it used to be 15/16” in diameter from
the splines at the end that fits into the differential is reduced to
7/8” from there to where it tapers upward to the bearing stop
surface. This makes that area a good deal more resistant to
snapping, as it provides more twist with the strain of starting out
or snapping the clutch, thus reducing that breaking-off malady in
the typical spot at the end of those splines.
Because breaking an axle has been a steady problem for over 50
years, I decided to see what I could do to try to help T owners by
getting this extra-duty shaft made by a company that has produced
axles for many, many decades.
Price, as of 12/7/2015 is US$150/ea.
More from Dave on installation:
At TD12285
(Dec 10, 1951): The wheel studs and nuts and all threaded fittings
in the drive shaft and rear axle were changed from British Standard
Fine (BSF) to Unified (UNF or SAE) threads. Most people will be able
to use their old nuts. I have new SAE nuts available for $12 each.
These are not available off the shelf in the thickness we need so I
have to machine them to size. It is a 7/8x14 slotted nut Grade 5.
The
suggested torque is 150 ft. Lbs with threads lubricated. Anti-Seize
compound makes a good lube. The WSM suggests tightening the nut to
85 lbs per foot and then to the next slot for the cotter pin if
necessary. By using the WSM procedure it could reach the 150 Ft. Lbs
but it is unlikely. One slot of turn will increase the torque
quickly at that point, especially with the BSF threads which are
coarser than the SAE. If you have excellent splines on your hubs you
could get by with 85 but that might accelerate the wear. If you have
marginal splines on the hubs you need to get the torque high enough
to try to keep them from wearing further. I suggest trying for as
close to 150 as you can get by swapping the washers and or nuts from
side to side to give you some options. Try not to go over 170 and
200 is absolute maximum. My new half shafts manufactured September
2012 and later have two cotter pin holes to choose from which makes
it easier to get the right torque. Some people have shimmed the hub
splines. Locktite makes a product to take up small amounts of wear
in the splines and it is recommended you use this if your splines
are worn. The drawback is that removal will take some heat to loosen
the Locktite.
Most bearings
are probably re-usable. In case yours are not the bearing numbers
are 7207 (unsealed) and I believe the sealed bearing is MJ1-1/4 2RS
which crosses over to the RMS 10 2RS. I am not recommending sealed
or unsealed, that is for you to decide. I do believe that if your
tapered collar is good and you install a new seal then the
non-sealed bearing will be fine for many miles. There is a spacer
washer under the bearing so you will need to have access to a press
to pull your old bearings off and press them back on the new shafts.
Rev. 3/31/2014
*******
An excellent description of the benefits from the
design and material of the new shaft has been proposed by Gord
Clark. He writes:"" ... by making the shaft of smaller diameter and
of a steel that is designed to absorb mechanical stress, the effects
of sudden torque on clutch let-out, allows the energy to be
distributed over the length of the shaft, ...." Dave Clark
adds: "I've torn down three axle cores now that had broken shaft and
all were at the spline on the inside end at the differential like
Günter's image. "
If you're in the Case One or Case Two situation you
can sit back, open up an
OSH, and
refer to Section H of the Workshop Manual for instructions on how to
replace your broken half shaft. However, if you're a Case Three'er
you might want to click on this link and let's see about
replacing a broken half shaft.
Let me add a personal note on this subject. The broken
halfshaft problem has long been an item of concern for T-car folks
who are inclined to do any serious driving. As a result, one
of the things in the back of the car on a trip is usually a half
shaft with an attached bearing, ready to be installed. I was
in that group. However, since I've updated to the new
halfshafts I've been able to leave my spare at home. I don't
know of anyone who has had a failure of one of the new halfshafts.
Next to converting to a 4.3 rear end I don't think there's a better
gift to give your T-car. Bud Krueger
(508) 317-9412
email to:Bud@Ttalk.info