Dimension Specifications or Allowable Wear

[Duckfarmer27]

I'm currently rebuilding a differential / rear axle. I've searched on this board, the net in general as well as my reference books. Might be I am missing something, but it seems finding a consolidated listing of allowable wear for various parts. Although I'm searching primarily for rear end data, I'm not tripping over other data either. Hence the question.

I did find a thread that listed allowable hub wear at the rear axle hub - https://www.fordbarn.com/forum/showt...ension+bearing - and my housings are within spec. The answer refers to "according to Model A Specs by Bob Rentz.". A search for such a book turns up nothing.

As a retired mechanical engineer who has been turning wrenches since he was a kid I do remember the days of going to a junkyard, getting the part and just throwing it in. Things ran fine. As much as anything, for my own curiosity, is such data out there somewhere?

Thanks.

Dale

[Kurt in NJ]

I have some spec from V8 book, 39,40 engine&chassis repair, publication "V15"
backlash between diff pinion gear and axle gear - .010
clearance between diff pinnion gear and spyder shaft -- .005-.008
axle shaft endplay -- .003-.006

when you use NOS parts it ends up in those ranges of clearances for the A too

[BRENT in 10-uh-C]

Originally Posted by Duckfarmer27

I'm currently rebuilding a differential / rear axle. I've searched on this board, the net in general as well as my reference books. Might be I am missing something, but it seems finding a consolidated listing of allowable wear for various parts. Although I'm searching primarily for rear end data, I'm not tripping over other data either. Hence the question.

I did find a thread that listed allowable hub wear at the rear axle hub - https://www.fordbarn.com/forum/showt...ension+bearing - and my housings are within spec. The answer refers to "according to Model A Specs by Bob Rentz.". A search for such a book turns up nothing.

As a retired mechanical engineer who has been turning wrenches since he was a kid I do remember the days of going to a junkyard, getting the part and just throwing it in. Things ran fine. As much as anything, for my own curiosity, is such data out there somewhere?

Thanks.

Dale

Dale, two thoughts apply to your question. The first one is that often times it is the original drawings of a particular part (-or assembly drawing), -or the Service Bulletins that lists acceptable tolerances and specifications. Those are somewhat troublesome to find at times however they are available.


The second side of your question is seemingly harder to find these days, and that is something that is call common sense, --or common feel. Back in the day, a good mechanic applied somewhat of a common feel or common sense to his craft, and he really did not need a torque wrench or even a micrometer to determine the serviceable life left in a part or component. Unfortunately in modern-day mechanic work, the mechanic often needs a torque specification along with a specialized tool to determine when a fastener is adequately tightened, ...or they just replace a component in lieu of repairing/restoring the component.

[Duckfarmer27]

Kurt -

Thanks for those - think I saw at least the backlash number in a thread somewhere.

Dale

[Duckfarmer27]

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Brent -

Thanks. I have to laugh - I'm used to having the prints around from my working life but of course do not have a set for a 90 year old machine. I actually am waiting for a set of service bulletins coming in the mail that I got off Ebay a week or so ago. Figure that will be a bunch of reading when they show up.

I have to agree with your second paragraph. That was the way I was raised - did not own a torque wrench for a very long time and things seemed to work out fine. Kind of goes along with making your own pullers, etc when needed.

Then I have to contrast it with where I am at and with my life's experiences - working on aerospace 'stuff'. Here I have two complete rear axle assemblies and want to end up with one good one. The one that was in my truck failed - you saw that in an earlier post. One axle housing is definitely in trouble where the wheel bearing fits, the classic ridge on the bottom from wear. Without prints and never having been into a Ford rear end before my head scratching was how good are the two housings that show no noticeable wear. Hence my search for what would be an OK dimension - as I would prefer to rebuild this rear end once, do it right, and not have to revisit it because I failed to check something out.

You are very correct as to skills and knowledge. And there is a definite difference. Most of my work life was getting things built, not doing the design. Ended up being a battle at times with design engineers who had never had to actually work on or repair anything in their life - and I had a reputation of fighting for maintainability/assembly common sense. I often tell one story - short version the responsible design engineer offered to help this one time. Here we are talking (if my memory is right) a 1/2 inch NC bolt going into some armor plate - program late due to design changes, pressure is on, normal life. I'm busy with my own problem two feet away and suddenly my one technician is jumping over me screaming at the engineer. He had reached torque, the wrench clicked and he kept right on pulling. Turns out he had never used a torque wrench in his life and had no idea what the click meant. Had other skills but mechanical assembly was not one of them. The tech was very particular - but then in an earlier life he had worked on nuke weapons. There were reasons why some of us saw things different than others!

Thanks for the reply.

Dale