Damaged Birfield joint. Usable?

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Oct 21, 2015
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Grove Hill, Al
I just tore down my left knuckle on 1980 HJ45, and came across this damage on the Birfield joint. This is my first time doing this. Found that bearing that you see sitting on the top of birfield, buried in the grease in the bottom of the knuckle housing. The strange thing is,,,Where did it come from? None of the bearings that I remove are missing any pieces. Its bigger bearing than the upper and lower knuckle bearings. Is it what caused that scoring on the unit? Just left in the grease by PO when he replaced bearings? Was this damage from 30 years ago?
I guess my main question is,,,,If I tear down the birfield, and dont see any inner damage, does that scoring on the outside matter? For a newbie,,,at what point do you buy a new birfield? What am I looking for?

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3_puppies

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what does the inside of the axle ball look like?

I'd find a good used one, any birf from late 1979 up to 1990 FJ40, 55 60 or 62
or solid axle mini truck from 1979 up thru 1985
 
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I've pretty much decided to just buy a new (or used) joint. I was a little confused about something. I keep seeing them advertised as 27 or 30 spline. I decided to count my splines to make sure I was getting the right one. My old one has 30 splines on the shaft at the outer end, but where the long shaft goes into the birfield is 27 splines? Excuse my ignorance on this. It's my first time tearing into one. When they advertise as 27 or 30 spline,,,,,are they talking about where the axle goes into birfield, or other?
 
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Although there is surface damage there doesn't appear to be any damage that would cause the birfield to fail. It may not look pretty but I don't believe anything critical. Smooth off any rough edges, clean it and put back together with fresh bearings.
 
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what does the inside of the axle ball look like?

I'd find a good used one, any birf from late 1979 up to 1990 FJ40, 55 60 or 62
or solid axle mini truck from 1979 up thru 1985
The inside of axle ball is perfect. No damage. I assume at some point this birfield was put in there already beat up.
 

FJ40Jim

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Although there is surface damage there doesn't appear to be any damage that would cause the birfield to fail. It may not look pretty but I don't believe anything critical. Smooth off any rough edges, clean it and put back together with fresh bearings.
The surface damage is exactly where the failure crack will start.
 

pb4ugo

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I've broken my fair share of birfields in the past, back B4 Longfields and Marlin was experimenting with the Marfields. In the last year that ran bifields, I had broken 4, and looked at my inventory of stk birf's and realized I had less than a year of wheeling left. I used to buy frt ends and rusted out 40's and 55's just for the the frt ends and birf's and part out the rest of the vehicle. You could buy frt ends for $50 to $100. I found the difference between a good birf and a bad one was looking at the open bell end and look for cracks where the bell was machined and thinned out for the balls. They start to crack where the open red arrow is in the pic. That's where the crack usually would originate and indicate it was going to break in the future. I would keep the birf in the OP's pic as a spare or maybe run it, because a stk birf at some point is going to break anyways if the frt end is locked, and if there are no cracks at these locations.
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