Is the flange ( the one on the third member) on a 3spd the same as on a 4spd except for the bolt pattern? Can I put a 3spd flange on a 4spd pinion?

What I have is a 3spd setup that I have no choice but to change the third member over to one from a 4spd. My 3spd rear end is destroyed and my spare is from a 4spd setup. I took the flange from the 3spd and eyeballed it over the 4spd and it looks like the same spline count and everything besides the 4 bolt pattern.

Since I have your attention what is the difference between the 4spd and 3spd setups? My lockright went in both and was the same part number for 3 or 4 spd.

When I change the flanges is there anything else that I must do? How tight do I tighten the pinion nut? Keep in mind that the third member and lockright is installed in the axle already and I just have to remove the flange and hopefully just swap over to the 3spd flange.

If the 4-spd setup is pre-1978, your 3-spd flange will bolt right up. In '78, all pinion flanges were fine splined, so a 3-spd flange would not work for these applications.

There is no difference in post '68 third members, whether they are 3 or 4-spd. The third members are the same from 1968-1989 or whenever the last FJ62 rolled off the line.

Just re-tighten the pinion nut to where it was before. I've had to switch flanges a few times and the only real problem I encountered was the fact that a 4-spd flange didn't fully seal when I put it on in place of a 3-spd flange. It just leaked a little, no big deal.

And not to mention the fact that if you have a 67 or older third member you can just replace the side gears for the fine spline ones and run them. I took my Dad's 67 third and just put in fine spline side gears, I'm currently running it up front in my Cruiser d44 hybrid. If you have a fine spine pinion you can just take a mini truck flange turn it 180 and redrill for your app. If you have a coarse spline pinion then you can get undrilled flanges or drilled flanges from CCOT or Downey.