Ttalk Tech

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.  They are of top quality design and material and are now available from Dave Clark at very reasonable prices. Dave can be contacted by clicking here on his name Dave Clark.

 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) 746-6735
Rev. 12/7/2015