3rd member compatibility?

[Big Sexy]

Gentlemen,

I just completed the 3rd member swap (3:73 to 4:11) on the front on my '79 piggy and now moving to swapping out the rear.

During this work, I noted that the 3rd member appears the same as front vs rear - makes sense from a production standpoint...

I have a pre '76 coarse / 6 spine axle parts from a trade taking up garage space that I thought were of no use to me. However, as I broke down the axle, I noted that the 3rd member end of the axle is 30 / fine spine - maybe useful after all....

So it appears to me that:

1.) I could use 3rd member from any year?
2.) I could use 3rd member in front or rear?

Am I right or wrong here?

Jeff

 

[Delancy]

Jeff,

You're correct.

Any third in any year, from any platform, straight across the board.

 

[Napster]

I know this is off topic but what tire size are you running? Looks like your axels are wider than stock, are those fj60 axels? Looks like a lift too?

 

[Big Sexy]

I know this is off topic but what tire size are you running? Looks like your axels are wider than stock, are those fj60 axels? Looks like a lift too?

Running 33" mudders. Stock axles. Lift was there when I bought it.

 

[PabloCruise]

I believe there are a few differences:
Flanges: three speed, four speed and Fj60s
Spider gear: early coarse vs fine spine
Diff mounting holes: early were 9mm while newer are 10mm

You are correct, there are some differences...
There are a variety of flanges used, and changes within 3 spd and 4 spd.
I do not recall when they went to fine spline axles.
Factory switched from coarse pinion to fine spline pinion for 1978. My 9/77 built 40 has coarse pinion.
Once the 80 series came out, the front diff is different, smaller, and reverse rotation.

 

[PabloCruise]

Pinion Flanges: