720 Diff Stub Axle Advice

[71Nissan240Z]

I've researched alot. And it seems you can swap the buttons on the 720 diff to accept a bolt in stub axle.

What do u think I'd the best approach. Should I just let the stub axles from my z float inside the diff. As a few have done that.

Should I get the stubs machined to accept the snap ring.

Should I swap the buttons. I don't have the proper tools to check backlash and pre load if I disassemble the diff.

Thanks.

[Zed Head]

I wouldn't let the stubs float.  They could get jammed if they get far enough out and cocked.  You're not really saying if you have a 720 diff that uses snap-in axles but I'd guess that's what you have.  The snap-in axles are fairly common.  I'd find a set of those, if that's what you have.

 

I've seen where people used a cutoff disc to grind a groove for the circlip.  It doesn't see any repetitive work, it only holds the axle in one spot.  If you get it in there, with a circlip on it, it shouldn't be a problem.  All you need is the dimension to grind the groove.

[71Nissan240Z]

The 720 is snap in style. You say I can find snap in style z stubs? I've never seen them. If I can't find it I'll probably cut a Grove into the current z stubs I have.

[71Nissan240Z]

Gee whiz spare stub axles on ebay are the same price I paid for the whole diff. I just need some spares incase I mess up.

[John Coffey]

The splined length of the 240Z side axles is not long enough to engage the snap ring if a groove is cut.  You need to add length to the splined section.  I used to do that by using three 240Z side axles and two of the long side axle bolts that hold them in place:

 

1.  Cut the splined section off one side axle and then cut that section in half creating two splined "buttons.".  Bevel the ends of the buttons.  The material is very hard and I used a water jet to make the cuts.

2.  Put the bolt through the side axle from the flange to the splined end and add one button to the splined section.

3.  Weld the threaded end of the bolt to the outside end of the button.

4.  Put the assembly in an old R180 diff and push it all the way down so the splines line up on the button and the axle.

5.  Weld the bolt head to the center of the axle flange.

 

This assembly is strong enough to hold the axle in place.  The only caveat is lowered 510s which tend to pull the side axle out of a snap ring R180.  I probably made three dozen pairs of these for people over the years.  I don't make them now.

[Zed Head]

That's some good information.  Copied and saved.

 

I don't really have any experience with the R180's.  Interesting that the 720 is snap-in.  Can you swap yokes on the half-shaft?  Put the 720 snap-in yoke on the 240Z half-shaft by separating the two at at the u-joints?  Create a new hybrid half-shaft?  Just an idea.  if John C. was fabricating hybrid axles in the past, that's probably the best route.

[71Nissan240Z]

John in theory I can swap the buttons inside the diff to a threaded version and should work right? I don't have a water jet. I know I'll have to verify pre load once i out it back together which may not be a bad idea anyways. I've only assembled one diff in my life. But I know how the measurements work. I just don't have a dial indicated right now. It was stolen from me and now my tools are always locked up. Thanks for all your help.

[John Coffey]

Yes.  Most folks just pull the threaded button out of their 240Z diff and put it in their snap ring style diff.  Instructions are on Hybridz.org.