Rear Axle Problem

[Woody Willy]

What started as a attempt to replace the axle seals on my rear end has mushroomed into something more. It is a "donor" rear end that I traded some parts for with 48K miles on it of unknown condition. After I removed the driver's side axle half, I discovered the driver's side differential housing bearing had broken off at the hub. The good news is that all the teeth and gears appear intact and show little sign of wear or damage. My question is when I replace the housing with a good hub, both sides will be changed, how far on the hub should the bearing be mounted? Both of the housing assemblies I have have the passenger side bearing mounted almost flush with the end of the hub, However the one driver's side has the bearing that broke was mounted about 3/16" onto the hub. I surmise that the bearings should be mounted the same on both sides of the housing but wonder why and if the broken hub was the result of mounting the bearing too far onto the hub. Would not this cause the bearing surface to not ride in the race of the axle half inproperly? Could or did that cause the breaking of the hub? It should be noted that the assembly was put together with the nuts on the bolts mounted differently from what I have seen on other cars, that is the bolt heads went in from the driver's side ring gear side and nuts were safety wired on the passenger side. Does it make a difference?

[Jim Kellett]

If I understand your post correctly you want to know how far the carrier bearings get positioned onto the carrier assembly. When you say "hub" I assume you referring to the outer ends of the carrier assembly. I have attached a photo showing the assembly. The bearings are mounted on the differential case with no spacing between the backside of the bearing and the shoulder on the case.

On occasion it may be necessary to place a thin (.005 to .010") shim between the back of a bearing and the carrier shoulder to get the proper value of pre-load on the carrier bearings or in some case to set the proper value of backlash with the ring and pinion gears. Normally this is not necessary so to answer your question: mount both bearings completely against the shoulder putting them on the carrier as far as they will go. You will most likely want to place the new bearings on a lit 100 watt bulb for about 15 minutes before attempting to place them on the carrier. The heat expands the ID just enough to allow the bearing to slide onto the housing. Without the heat it is nearly impossible to get the bearing in place.
Hope this helps

[Tom Endy]

Woody Willy:

When mounting new bearings on the carrier hubs it is important that they mount with an interference fit. Nine out of ten carriers I encounter have had the bearings "spun" on the hubs due to improper carrier pre-load adjustment sometine in their history. This not only machines metal off directly under the bearing, it also machines metal off the bearing stops.

If the hubs you are going to use do not accept the new bearings with an interference fit it is adviseable to have the hubs knurled. How far the bearings fit onto the hub before it is up against the stop is only important when it comes to setting the carrier pre-load. If you are not able to achieve the proper pre-load with the banjo gaskets alone, you then can remove the bearings and add shims under them. Bratton's carry the shims. They are .005 thick. It is best to purchase a number of them because you may have to add more than one on each side.

Almost every differential I overhaul I have to replace the carrier with one I have had knurled. I exchange them and send the carriers out in a batch for knurling. Very often I have to add shims under the bearings. I have the machinist doing the knurling write on the carrier how much he took off the stops on each side in order to clean it up. This gives me some idea how much to shim. The whole process is however, is trial and error task.

If you are not familiar with the differential re-building process I invite you to use a disertation I put together a few years ago.

Go to the web site of the Orange County Model A Ford Club (Southern California) at www.ocmafc.com. At the home page there is a menu at left. Scroll down to tech articles and click. It will bring up a new menu. At the top is my name, click on it. It will bring up another menu of technical articles. Scroll down to the one on differential rebuilding and click on it. The file is an adobe file and it will take a while to load. You can down load it and print it out. It is free to use. It should answer all your questions. It includes 42 photos.

Good luck with your project.
Tom Endy

[Brentwood Bob]

Refer to tom Endy's writeup. It will systematically walk you thru the entire differential rebuild. Make sure you throughly clean everything , housings, torque tube prior to rebuild. Also inspect the tapered ends of the axles for cracks and a worn keyway. Bob

[Woody Willy]

Thank you to all that answered by request. After reading the tech article it appears to me that, 1. I am way over my head. and 2. That I do not have the tooling required to do the work. I am going to either find someone local for help with the tooling or locate another rear end to use instead. One last question, how can I check out another rear end, that is removed from a car, to determine it's usability? Again thanks for the information, you have been more then kind in offering your knowledge of the Model A. Regards, Bill Huminski

[Tom Endy]

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There is no absolute sure way to determine the health of a rear end assembly removed from a car without taking it apart. You can crank over the drive shaft using a ratchet wrench and a six-point 1& 1\16" deep socket, which will fit the spline. If it appears to crank over smoothly it will probably work. Beware of rear ends that have been removed from a car for sometime. People have a habit of leaning them up against a fence with the open mouth of the torque tube facing the sky waiting for it to rain. Also there is probably a reason why it was removed.

Rebuilding a differential appears to be a daunting task. However, it is not that difficult. It is more tedious than anything else because to do it right you have to partially put it together and take it apart a number of times. Most of the special tools can be improvised. As far as measuring pre-loads, this can be done by feel and be fairly accurate.

Tom Endy

[Brentwood Bob]

Depending on your location contact a local club. the members have probably done this job and can walk you thru it. For years I avoided this area of the chassis. Once I went thru it it was not complicated, or undoable. Just takes patience, and tenacity. I believe I could teach a 12 year old. Bob

[Brentwood Bob]

Willy, That didn't come out quite right. If you managed to take the rear end apart, you are able to reassemble it. Tom's dissertation will do the job. It would go easier with someone looking over your shoulder. The same goes for evaluating other rearends for replacement 2 pairs of eyes will work better than one. Bob

[Woody Willy]

No offense taken, you're right I got it apart, I should be able to put it together. I am located on the East coast of Florida, the nearest club I know about is about 75 miles from me. There are a couple of Model A 'ers nearby and I lean on them for help. As you say not many people have gone into this level of teardown and rebuild, I'll try to complete it by trial and error method. Education will result from that effort at least.
Again thanks for your advice an encouragement.
Bill H.

[Brentwood Bob]

Carry on. The rules Tom brings out will get you thru it. The differential seems to be forgiving. If it is noisey when reassembled, take it apart and redo. I have done several now and learn from each. Bob