1976 280Z Restoration Project

[ConVerTT]

4 hours ago, wheee! said:

Time for a mythbusters episode!

The half shafts are absolutely identical. No one side longer or shorter than the other. 

@zKars

Mind blown!  I would not ‘have believed it without pics.

[wheee!]

How much grease was in those half shafts? They look like they have gotten a little warm at some time

Ughhhh. A ton....

[zKars]

We 'know' the distance from the flange faces inner/outer on each side of the diff are different, as the Rxxx diffs are intrinsically wider on one side. The modern world (1980 and later) knows only of CV style joints that have very little in/out slop and have to be carefully sized to fit. Thus it was natural to assume that our lowly old school shafts would 'have to' be different lengths to 'work' in our unbalanced ancient hot rods. Wrong. Even when directed to the Z parts manual, where never the words 'left and right' could be found in the listings, they still disbelieved.  

What was never properly understood was the massive (by comparison) length variance our marvelous half shafts are able to supply. They do gum up, and often true that you can't compress them by hand all to the same length, or perhaps expand them to maximum for the same reason, which only added to the 'they are different' myth.

And I've never heard of one breaking anywhere but at the u-joints themselves. Marvelous engineering indeed.

Edited February 3, 2019 by zKars

[grannyknot]

If I hadn't seen those pics I wouldn't have believed either, the measurements that I have done always showed the P/S was longer than the D/S.

I guess the grease inside packed up and hardened into the limits of travel and that's what gave the different lengths, anyway it's nice to see that settled once and for all, at least for all of us non believers.

[wheee!]

I’m glad this post has enlightened more than just myself. Thanks to Jim for suggesting I report my findings.

[wheee!]

Well, that’s one restored! I added the 10g of grease to each of the ball tracks and another 30g in the top section beneath the snap ring. The manual has no info on adding grease to the boot itself so I assume that is left dry? Catches the oversling later?

[Namerow]

The 280Z FSM is pretty explicit about the places where grease should be applied... and the dust boots are not one of those places.  I guess it's tempting to think of the boots as grease reservoirs that will help to replenish the spline and roller regions over time, but centrifugal force will keep that 'reserve' grease trapped up in the outer boot folds, well away from places where it might do any good.  Maybe just a light smear to lubricate the boot surfaces in case they rub against each other at extreme axle deflections?

[zKars]

It's a week for dispelling myths I see. First half shaft length difference, and now how grease works.

I once believed that wheel bearings need to be filled with grease, including the dust cap. Have to keep grease around to replace what gets flung and maybe moved with heat and motion, right? Fill the bearings of course, and stuff as much in the cavities as you can. Tough to put in too much! 

At the same time I was doing more R&R's on rear bearings as well as fronts, and what struck me was the lack of grease in especially the rear housings. The bearings them selves were packed full of grease, quite often quite clean grease which I found surprising given that these were original bearings (spline nuts still had perfect factor peening). Maybe a light coat on the distance piec, but the cavity spaces are bone dry. 

But finally the light came on. Why in the world would you want grease that leaves the bearings with heat or centrifugal force and needs to be replentished by what's around? I cannot imagine a scenario that enables grease to move around in there and properly keep the bearings greased unless the entire cavity was packed full.  Grease is actually designed to stay exactly where it is put and NOT to leave the bearing races at all under any but the most extremes of heat, up where metal starts to glow. 

The enemy of grease is moisture and dirt/grit/brake dust. If your seals are bad, that crap can get in there and destroy the bearing. I had a front failure due to a bad (ok, absent o-ring on the dust cap) and no wheel center caps that allowed crap to get in the bearing space and eventually lead to lock up and failure. My fault 100% as I was only putting grease on the bearings by this point,. So there IS a reason to put lots of grease in front of the spindle nut inside the cap, but it's mostly about a barrier to crap getting to the bearings.

So there is no need to put grease anywhere but directly on the parts that touch and move. Once there, it does not move or migrate away. Any grease you put in that axle boot will stay right there and never contribute to the sliding joint. Might keep the boot soft and snuggly, but that's it. 

[wheee!]

That's what I was thinking! But the boots both came apart full of the cruddy yellow goop that was also inside the shafts themselves. There is no o-ring or seal between the boot and the shaft, just the snap ring and collar. There is a small amount of "residual" grease in the boot from sliding it onto the shaft and being handled with greasy gloves, but nothing excessive. I will seal up the boots with the cv bands when they arrive and be done.

[wheee!]

[grannyknot]

Where did you find the U joints with grease nipples? I didn't think they were making those anymore.

[7tooZ]

Spicer 5-1505x fits



72 body and block, everything else 71, Tokico springs, Illumina, R180 CLSD, 83 close ratio, 3.90 gears, Ztherapy SUs, BRE 15X7 Libre wheels and BRE front spoiler.