Rear Differential Pt. 4

I know I've talked about differentials a lot, but -- for me, at least -- there's good reason to do so. I'm not sure if I mentioned this in a previous post, but when I acquired the truck in the first place it was in decent-ish shape. Through the process of disassembly and inspection I have learnt that there are a few things I would like to change and / or refresh. 

Normally you wouldn't really dig into the differential unit at all during a rebuild.

I'm obviously not normal so I reckoned, not without hubris, that I could mix 'n match some parts to make things better. Initially, I wanted to replace the original axle case because of the deep channels worn into it by the u-bolts. Replacing that necessitated pulling the whole axle apart to re-use the differential I had. Then, naturally, I thought that since I had it opened up I'd check it over and make sure all was tickety-boo before mounting it to a replacement axle case. 

Dear Reader, don't do what I did. Just find another axle, paint it, and go. 

The Haynes manual famously suggests that you not even attempt any work on the diff, diff carrier, or ring & pinion. It can be quite complicated and it is arguably one of the most precision-y things on a Land Rover. There are preloads, backlashes, and heights to set. Some of these operations require special tools. It's a hassle to do yourself which is why diff work is generally quite expensive. 

Whatever. 

A while back I bought a dial gauge with magnetic mount from KMS Tools on sale. Throughout the workshop manual you'll see various references to using one of these tools so, I thought, it seems prudent to get one.

As is so often the case however, buying tools is a slippery slope where capability and reasonableness trade blows in an endless tilt. Once I had a dial gauge, there really wasn't any excuse to check the crownwheel (ring & pinion) backlash, was there? 

This is not, on its surface, all that hard to do. You know from my previous posts that I had already removed the bearing cap bolts to clean and inspect the differential unit. So it wasn't too hard to loosen them off, then move the cage nuts to get the backlash more-or-less where it should be. 

And d'you know what? It worked. 

Please excuse my overfull workbench.

Interestingly, the dial gauge doesn't come with instructions. Of course not! This is one of those things that in the Real World would be demonstrated by a greybeard to an apprentice. No one tells you how to use one or indeed what the marks on the gauge represent. You sort of have to intuit it if you've never done it before. 

And before the entire Internet (or the two of you that are reading this, Hi Mom!) come down on me telling me that there is a scale printed on the face of the dial indicator, there is a skill in connecting that to what you see in a shop manual. One needs to convert hundreds to thousandths and check one's results against common sense. It's actually kind of an intimidating problem to solve if you've no one around to say, "that's right." 

Carry on, then. Just one more of those 'how hard can it be' Clarkson moments and it feels sort of correct. After setting the backlash -- it only took about 15 minutes of fiddling to get right -- I safety wired the cap bolts and the, uh, penis thing that keeps the cage nuts from unwinding, then hit the whole innards with a good spray of Honey Goo to preserve the diff as it's not clear when it'll be running and / or bathed in oil properly again. 

Job done.

Except now that I set the backlash correctly, the whole differential feels... tight. My memory flashed back to a previous day when I pulled out the razor-thin remains of one of the pinion preload shims and chucked it in the bin. 

Maybe I should have bought a fish scale and shim kit and set the pinion preload according to the directions in the shop manual?

More tools, more problems.