Putting '73 3rd members with 4.88s into my 86 FJ60. The 3rds are just rebuilt with no miles on them. Can I just pull my 3rds and swap the pinion flanges? The '73 3rds should use seals not crush sleeves so I don't have to pull the entire pinion, right? Then just torque it down to spec. Sorry for all the questions on this topic but I've never done this before and I ain't payin' the shop the $450 they quoted me to put these 3rds in.

It all depends on wether the 4.88 pinions are coarse or fine splines. If they are fine (which I am not sure but I do not think that any aftermarket pinions came with the coarse splines) which they should be it is fine taking them off and swapping them.

IIRC, ALL aftermarket gearsets use fine spline pinions. 77-older Cruisers all use the same coarse spline pinion flange. 78+ Cruisers "all" use fine spline pinion flanges.

Most aftermarket shops also carry replacement flanges...some are also un-drilled so you can pick-choose your driveshaft bolt pattern.

ANY shop should be able to offer you a decent price to check preloads and lash measurements, especially since you've gone thru all the effort to remove the center section.

In regard to the preload, all the aftermarket cruiser R&Ps I have seen can be set with shims, but they may also be set using a crush sleeve at the choice of who did the work. (I could be wrong, since I have only seen a few). If it is set up with shims, then you can just swap the flanges and torque them back down and stake them. You are done. If they have crush sleeves, then swapping flanges is more complicated. The best thing would have been to give the shop that set up the 3rd members the correct pinion flanges, since they are going to be guarantying the work. If this is already a done deal, then the second best would be to swap them and use a new crush sleeve. This is a PITA as you will need to remove the seal and the outer bearing race. You can still swap them if you are careful: Measure the overall preload with an inch pound torque wrench. Then change flanges and tighten a new nut just enough to give you the same original preload and stake the nut. A few degrees either way can make a big difference in the preload.

Well thanks for the input guys. I think I will pull the diffs on my 60, take those and the new diffs in to a shop, have them swap the flanges and verify setup (got quoted $40-$50 for this) and then put the new ones in. Anyone need some 3.70s setup for FJ40 drivelines?