912 Axle

The cars came with Nadella or Löbro half shafts. Löbro have CV joints covered with rubber boots. The Nadella have an exposed universal joints. This discussion refers to the Löbro half shafts (Spare Part No. 901.223.026.10).

Mine have been converted to Löbro with CV joints. Nadella are no longer in the parts chain. It has been suggested that the CV joints should be re-packed every 60K miles. There are 6 bolts at each end of the half-shafts that are removed with 6 mm hex wrench. The factory manual suggests these be replaced after removal. They are torqued to high enough values to stretch the bolt by design. The factory supplied bolts are expensive - perhaps close to $2 each. After market or bolts used on later cars such as the 914 are available, but they have 12 point socket heads, similar to those holding on the door hinges. It takes a special wrench. The bolts on my car are 45 mm in length measured from the end to the bearing surface on the head. Swepco makes CV joint grease. It takes a couple of tubes - 2 1/2 oz per joint. The job is pretty messy. The boots are held on with inner and outer metal clamps. The boots on later model cars were crimped to a metal flange of some sort. The inner clamps are readily available, but the large diameter outer ones take a bit of searching. Some people (racing community) use heavy duty tie-wraps for these. I've tried this technique with success. The rubber boots are available. The joints should be cleaned and inspected. If there is any scoring on the sliding surfaces, the parts should be replaced.

New complete half shafts with both CV joints are about $290 each. 'Rebuilt' ones are cleaned inspected and re-packed. If the inspection shows any problem, they are often replaced with used parts. They do not have a good reliability history.

I've seen 'new' half shafts in boxes at swap meets for $100. This is worth a careful inspection. Buyer beware.

There is a company that re-manufactures CV joints and knows about early Porsche ones. See CV Source, Inc. in Norcross, Georgia.


The picture is one end of a Nadela shaft, but shows the Allen bolts.


021001-199 1. Set the hand brake to help 'breaking' the bolts loose. Raise the car and remove rear wheels. Place some newspaper under the car to catch the accumulated dirt and grease that will fall down.

2. Using a 6 mm Allen wrench, remove Allen bolts from half shaft flange, knock the half shaft from its seat and remove.
021001-202 3. Orientation was important in re-assembling if the parts are warn and is hard to discover. There were blue paint marks on the outer surfaces of the flange and inner race. Clean both enough to see these marks before they are taken apart.

4. Remove the original clamps around the boots and slide the large end off each of the flanges.

5. Remove the C-ring at each end with snap ring pliers.

6. With a hammer or mallet and a piece of wood, tap the spline away from the housing.

7. Slide the old boot off.


021001-208 1. Clean up the parts. The grease is messy, so work on newspapers and use paper towels to clean as much of the grease as possible. See the notes with this picture on hints to reassemble.

2. Check CV joints in half shaft for play or scoring on the sliding surfaces. If they are worn, replace.
021001-205 3. Here is the large flange showing wear marks in the groves where the balls ride.
021001-207 4. Similarly the inner race shows wear in the grooves as can be seen in this picture.


Re-assembly is tricky. The best technique is to use the painted blue marks across from each other as on one of my CV joints. Another way it so use a center punch and mark a point on both the inner and outer piece and to put them back together with the marks lined up.
021110-1446 Failing that here is a clue using the CV joints from Craig Norton's 1969 912. See the text with the picture.


021001-204 1. The picture shows the parts purchased so far. To facilitate installation of the new boot, wrap the spline and flange with aluminum foil. Slide the new boot on then remove the foil.

2. Re-pack the boots with new MoS_2 (molybdenum disulfide) grease. The manual says 2 1/2 oz. total for the boot and universal joint.

3. Install the new clamps, making sure that the worm gear screws don't obstruct the bolt holes.

4. Replace the housing over the spline and tap on far enough to receive the C-ring.


There is a washer on the inside of the universal housing. Be sure it is there and oriented properly.

Replace the C-ring.

5. Put some more grease on the joint faces just prior to assembly.

021001-201 6. Clean the old grease out of the receiving flanges on the car. Grease will be forced out of the boot through the cage and into this cavity from the repacked CV joint.

7. Release the hand brake, then install the half-shaft assembly.

8. Tighten Allen bolts in half shaft flange to prescribed torque: 4.3 mkp (33 lbs/ft); the Schnorr washer for the Allen bolt must face the base plate with the hollow side.


The Löbro half shafts may be fastened only with Allen bolts M 6 x 45 DIN 912 - 12 K. Spare part Nr. 900.067.073.01 (minimum tensile strength of 120 kp/mm2). These bolts bear markings 130 - 140 or 12 K, respectively, on the head or the side. There are 6 of these at each end.

Also the manual says the flange surface of the half shaft must be free of grease at time of installation - probably impossible to accomplish.

Last modified: Sat, 10 Feb 2001


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