Worm drive axle Reassembly

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    Through the help of Bob Jacobsen, the axle he had on the floor for 40 years,his pals on the west coast, Greg Long, David Coco and Fastenal and Ebay/Amazon bearing searches. I now have the pieces to put my ’33 Timken Worm drive differential together.

    After taking off the axle trumpets at Fastenal, I was able to fit it in to the trunk of my car, which is really small. I was able to dismantlement the center diff in about 1/2 hour (amazing what experience and parts that are not rusted together do to speed things up.

    Since everything moved in this axle, I was better able to determine how it goes apart. From left to right in the picture below are the items to disassemble. The left ring is held on the case with a dog with two drilled and wired bolts. It unscrews counter clockwise, I used a punch on the ears.

    The next ring screws inside the first ring and then screws into the base plate on the right. You turn the middle ring to move the bearing cup to the left or right to adjust tooth mesh. Repeat for the other side. Then remove the base plate. There is only one that is removable and it just taps off the studs. This gives you access to the carrier bearing.

    Pull the carrier bearing towards you (you might have to lever it). Your objective is to dislodge the opposite carrier bearing from its cup. Imagine you are trying to pull the bull gear out of the side. Once clear of the cup, carefully drive it towards the center until it drops. This will give you enough clearance to remove the bull gear and carrier out the side.

    I will get the new stuff cleaned up, layout all the parts and start reassembly later.


    This task is a perfect example of never say never. I’m impressed with your persistence Bill-Bravo!

    And like the song goes ‘a little help from your friends’


    Here are the spider gear parts exploded. You basically have a 4 axis cross piece with 4 (small)spider gears and concave brass washers on the outside and a pair of (larger)splined gears that the axle shafts slide into. These have brass thrust washers that fit between the gear and the carrier housing


    Here is the assembled cross piece. Notice the dished brass washer on the 6 o’clock gear. Each gear has one.


    These are the 2 carrier halves (R&L). They are not handed as they have the same part number cast in them along with the Timken name. The carrier on the left has the Timken #3984 bearing installed on the hub and the right one is before installation.

    I mic’ed the ID of the bearing and the OD of the hub and there was .002″ of interference. I got a plastic freezer bag and put the hub carrier in it in the freezer for about 6 hours. It shrank .002″. The bag helps hide it from the wife. I hate explaining, “What is this and why is it in my freezer.

    Similarly, I hide the bearing in aluminum foil and put it in a 250 degree oven for 30 minutes. Take the bearing out first then the carrier. The bearing dropped in place with a slight tap.

    Warning, this is best done when the wife is out as she may object to the use of her kitchen appliances as shop tools.


    Next the splined axle gear is inserted into the carrier (flat brass washer goes between them). The carrier splines are aligned with the splines in the bull gear and the carrier tapped in. The carrier won’t just drop in, it takes force. This is completed with the sequential tightening of the through bolts later. Be sure there are no burs along the edges of the seating area for the carrier.

    Photo shows gear in carrier and carrier in bull gear


    Here is a side view of the half assembled bull gear.


    Here is the spider assembly inserted in the bull gear/carrier assembly.

    Be sure all surfaces are clean and have no burrs before assembling.


    Now insert splined gear in the other carrier and line up the 4, 1/2 round indentions where the spider carrier sits. There are 4 ways to line up the spider carrier indentions. The holes won’t line up in all cases.

    Be very sure you have them lined up because you can put the halves together and not have them aligned. I inserted 3 bolts to help with the alignment.


    The through bolts are 3/8 x 2 1″2 and are drilled for castle nuts. Grade 8 would be preferred, but with all the splines, nothing is going to move.

    I alternated the entry sides.


    Here is the completed assembly. I measured the distance with a straight edge and a caliper from the rim of the carrier (where the bearing went on) to the side of the bronze gear to ensure everything was centered. Took measurements a 12,3,6,& 9 o’clock on bot sides and they were within a .001″

    Just need to align the holes in the bolts and install the cotter pins and this part is done.

    On to the worm gear and the case assembly.”


    Here is the exploded worm gear components. The front of the car is to the left. The first bearing (from left to right) is a Federal 1307, the next cone is Timken 43312, the next two bearings are mounted back to back and they are both Timken 43131 followed by another 43312 cone.


    Here is the worm gear with the front 1307 bearing installed, the case with one of the43312 cone and the worm gear sleeve.


    Here are the case halves. Due to the amount of brass and casting grit I sprayed the inside of the case with Glyptal, which is a product GE developed to insulate electrical components, like armatures, and gear cases. GE sold the business and there are other manufacturers.


    One of the odd parts is this shield that the worm gear rides in. There is a tab that fits in a groove in front of the rear bearing cone. To install you have to squeeze the the body, insert it from the front of the case, with the end with the tab leading. When compressed it just slides in and locks when you release it.

    This shield also prevents you from being able to just slide the Bull gear in or out if the carrier bearing cones are in place. More on this later.


    I compressed the end with a pair of slip joint pliers, slid it in as far as possible then reached inside, squeezed it with my hand, slipped it in place and then released it which locked it in place.


    Here it is in place. Worm gear is in the freezer, I will try assembly tomorrow.


    Great post. I wish we would see more like this. Thank you, Ed.


    Ok, here is the complicated part. Freeze the worm gear with the front bearing and the 43312 cone. Heat the 2, 43131 bearings to 250 degrees.

    Quickly, drop the worm gear in the front of the case opening, it should drop in with little force. Take the bearings out of the heat source and place on the shaft of the worm gear at the other end. Bearings go on back to back. You will have to drive them on (put case and shaft vertical and drive the bearings on from the top. Next, install the other frozen race at the rear of the case. Install the “D”” washer and castle nut.”


    I was unable to drive the bearings all the way home, so I temporarily attached the front flange and bolted a flat bar to 2 of the flange holes.

    I then got out my favorite Pierce tool, the 3/4″ drive 38″ breaker bar, and tightened the rear castle nut until the cotter pin holes lined up and there was minimal end play.

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