Jump to content

Diff inspection


Recommended Posts

Just had the diff out and apart.
Crown wheel and pinion look fine, no obvious wear or marking. Looks like a perfectly good gear set.

Meshing looks ok too to me.

Baklash is just enough to feel, not a huge amount.

The carrier came out ok, felt like a firm fit but not overly tight with the shims in it at the mo. It certainly wasn't loose.

Bearings look and feel ok.

Only thing I think is not ok is the pinion preload. It turns dead easy also with a finger. Should be tighter than this shouldn't it?

12-16 lb should be about 1-1.5m which is about as low as my torque wrench will go but it is nowhere near as stiff as this to turn.

So is it going to be new shims for pinion?

Am I right in thinking the shims on the inside of the diff bearing adjust the pinion position/meshing and the shims on the outside between the outer bearing and the spacer adjust the preload?

If that's right I'll probably leave the inner shims and carrier shims as they are so the meshing and backlash should stay the same, and I'll just go for adjusting the pinion preload.

Haven't had the pinion out yet as the castellated nut is crushed onto the thread so I'll probably have to split it.

It's a 4:11 MkII spit diff, was starting to get a bit noisy at high speeds on acceleration, no noise when backing off.

Thanks for any advice, and best wishes to everyone.

Link to comment
Share on other sites

I'm just swapping diffs at the moment & changing output bearings & seals on the newer one but I'm not going to touch the pinion preload/meshing.

Just re-reading some advise from Dave Pearson, what do the teeth look like? My old noisy one the teeth are so shiny I can see my face in them! On the newer one they're dull & you can still see machine marks.

Link to comment
Share on other sites


'Pre'load is just what it says and is at least partly an allowance for running in and subsequent wear to the bearings.  Therefore you should not expect a preloaded bearing set that has run for even a short time to hold the same preload torque.

Provided you have not got to the point where preload is replaced by more than a hint of free play I would leave well alone.  Certainly re-shimming the bearings to eliminate play is a risky business and really the bearings should be renewed.  If you must reshim, then you should only shim sufficiently to just remove free-play and definitely not try to re-instate the new bearing pre-load figure which would cause rapid failure!

I have know diffs with considerable pinion bearing free-play to go on for ages without a problem.


Link to comment
Share on other sites

Hi Charlie,
Yep teeth are shiney.

You mean this thread

Dave was saying shiney teeth are scrap, Garreth seemed not to agree.

Think I'm gonna have a go anyway because there's no scuffing or pitting or uneven wear.

Look pretty much like the teeth in this

Hi Nick,
Yeah was gonna go for less than with new bearings. Probably about 5-8 lb instead of 12-16.

That link above on rebuilding a Nissan diff sez
The preload limit for new bearings is 16.5 - 22.6 inch lbs.  For used bearings, the preload limits are 7.8 to 11.3 inch lbs.
So sounds like for old bearings you should about half the preload for new ones.

Just really thinking of adding a very thin shim, there are 5 thin ones on at the mo, just to get  the pinion so it's just stiff to turn.

Thinking about this, adding a thin shim between spacer and outer bearing will also move pinion in by same amount, so the meshing will be closer. Or no?

Anyway after geetting the preload right on the pinion I'll check the meshing with engineers blue then think about changing the meshing by adjusting the carrier shims, maybe trying for closer meshing.

Link to comment
Share on other sites


This topic is now archived and is closed to further replies.

  • Create New...