Rear differential identification help

Joined
Aug 30, 2012
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44
Location
Southwest Colorado
I am trying to get a 1977 fj40 back on the road but have a broken differential for starters. I have a rear differential from an unknown year. Are the differentials over the years interchangeable? I understand driveline connections changed slightly and that could be an issue. Any advice is appreciated. Thank you.
EAE6A1D6-EC01-4CC8-8A03-DEF8BEB2F5D9.jpeg
A44BD4E1-6B48-4DB0-8461-7C25A4CFF746.jpeg
A63E0C3C-76C9-44F7-BA9A-EC691FD95C6E.jpeg
 

pb4ugo

SILVER Star
Joined
May 8, 2006
Messages
2,586
Location
spay-lay-wi-theepi, Ohio
Yes, 3rds members are interchageable, just be sure it has the same gear ratio as you are replacing and it also has to be the same ratio in the frt. The 3rd member in you last 3rd pic has some sort of aftermarket locker, it may have and aftermarket gear set. .
 
Joined
Apr 21, 2005
Messages
21,439
Just be sure the replacement has fine spline axles. Some time in 1968 the spline went from corse to fine. You could switch the side gears in the diff but that would require setting up the ring and pinion. Would be easier to replace the input flange. Diff with fine spline side gears will either have the three speed bolt pattern or four speed bolt pattern for the driveshaft if from a US market FJ40. 1/78 pinion went fine spline. 1/79 went from 4.11:1 to 3.70:1 ring and pinion.
 

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