The differential rebuild has been quiet, since I didn’t realise how important one of the special tools was. Typically I can just make them, or make do with something else, but the tool for setting the pinion height is important. There’s plenty of advice floating around on forums saying “just use the old shims even if the bearing is a different height”, but these inevitably come with the warning that the rebuilt differential will be noisy. And besides, someone else has been through my differential before, so there’s no guarantee the existing shims are at all correct.

So I needed this tool. And there aren’t many left.

There was one for sale on eBay, but it’s unusably rusty:

Rusty gauge block

That gauge block fastened to the top of the cylinder needs to be accurate to +/- 0.02mm, so clearly that’s not going to work.

After quite a lot of time looking, I sourced another, and figured I’d post the dimensions on this blog so that anyone else looking for this tool can save a bunch of time and money and simply make one (or get one made). It’s a simple thing - just a cylinder and a block. The original one has some fancy end caps and a long threaded rod to keep both of those bits together, but it’s not necessary.

Anyway, here’s some pictures of what I sourced. (That’s not rust on the cylinder, just some protective wax from storage.)

Profile view of cylinder

Overhead shot of cylinder installed on differential, with gauge block underneath

Profile shot of cylinder installed on differential, with gauge block underneath

Far shot of differential with tool installed

As you can see, this thing is in great shape, so I feel pretty good about posting the dimensions here.

Cylinder:

  • Length 187mm +/- 1mm
  • Outermost sections: OD 73.32mm +/- 0.02mm, width 15mm +/- 1mm
  • “Shoulder” sections: OD 76.28mm +/- 0.02mm, width 24mm +/- 1mm
  • Centre section: OD 76.28mm +/- 0.02mm, width 53mm +/- 1mm

The un-machined gaps between centre and middle sections are about 25mm.

The gauge block is 63.54mm x 12.26mm x 37.00mm, all +/- 0.02mm.

With this, I’ve been able to progress the differential rebuild - I have the pinion height set perfectly, albeit with a lot of faffing about since I don’t have the special tool for removing the inner pinion bearing that the shims go under.

I’m currently waiting for parts again - this time some shims for the flange end of the pinion, where I need a bit more distance to get the preload correct.