Rear Differential Pt. 1

Alright. Time to put in some more work on the rebuild. I came across the Trailerfitter youtube videos some time ago and watched his series on rebuilding some newer-style (Disco) LR differentials. Since I now own 4 (5?) Series Land Rover diffs, I figured I would start working on cleaning one up to go in the rear axle. I'd gotten a start earlier this year when I cleaned up a diff by degreasing it a little. It was in relatively good shape, but needed a thorough cleaning. In retrospect, I probably should have pressure washed it first (usually good advice) instead of tackling it by hand. It was a fair lot of labor and a not inconsiderable amount of degreaser. 

Oh well, lesson learned. 

Anyway, on to the diff:

As you can see, it's in pretty good shape overall, at least looking from the exterior. You might wonder why I'm disassembling it at all, given it looks to be pretty decent. Well, I wasn't 100% convinced it was as good as it looked. I figured, since it was already apart, it might be worth pulling apart a bit further, just to check. I did this knowing that I left the diff carrier unbolted from the axle,  in a corner of the garage for spiders and dust and sh*t to get in there all over the summer. Which was probably not great for the bearings. If you're thinking of storing your machined parts out in the open, don't do what I did! 

Guys, you know when you get that feeling by reading the signs that you're not the first person to get inside of her? We all know those moments, right?

Everything looks pretty nice as you start to unbutton it, only... wait, is that an 18mil bolt on the bearing caps? Hmm. That'd make the pinion nut a 26mm, wouldn't it? Yeah. Did they use metric fasteners on pre 1980 rear differential housings? And those witness marks nicely punched into the bearing caps to match up each side, along with punched marks on the cage nuts? Looks like someone did a good job on a rebuild at one point. 

Alright, well, onward. 

Crown wheel looks mostly OK. Pinion looks pretty OK. Wait. Is that a big chu--

--nk? Chunk. Gouged out of the housing. Yeah, yeah it is. Now we know why someone was in here before. Should have known from the big cut in the housing at the top of the picture, above. Oh well, doesn't look too bad. Taking a closer look at the crownwheel, though, there's damage to at least one of the teeth:

... but that actually doesn't look too bad. It's not on any of the mating surfaces and it's on the heel of the crown wheel. But now that I look at it, I'm glad I decided to pull the whole thing apart. Lets me check some other stuff. 

... like the little bit of wobble on the sun gear here. It's... not great, I think, though I'm not an expert on Rover diff centers. This will merit further investigation for sure. I think it's probably out of spec / unserviceable, but perhaps someone more knowledgeable than me can take a look. I don't believe these older diff centers have thrust washers in them, so if it's wobbly it's probably kaput.

I am glad I am taking it apart, actually. There's some schmoo on the bearings as I disassemble it. You can see in the races that there's some stuff which looks a little metal flaky to me, so it probably needs at least a good cleaning. Race surfaces all look really good. Bearings feel really good. 

And really, everything looks pretty alright. The pinion, flange, and shims all look to be good. The pinion bearings were replaced by SKF units, and they feel pretty good. 

Job done for now! I don't think I'll take it down any further, as I don't have a press or a bearing puller OR a dial gauge (and expertise) to measure the pinion depth, etc. I'll probably have to figure out what to do with the differential centre, too. Anyone have a 4-pin diff center kicking around that's in great shape? 

I'm starting something new with my posts where each time I do one, I'm going to feature a "tool of the day." I've spent a lot of money on tools, basically having started from mostly nothing (a socket set, crescent wrench, and a hammer) to where I am now with a bunch of stuff I have used some of the time. This won't be about making tool recommendations necessarily, but will rather show you what I used to accomplish the job along with some notes about it so newcomers can learn from my mistakes.

First up is a set of punches.

You need a set. There are special tools you can buy to ratchet off the cage nuts (bolts?) holding the diff center in place. But, I hate buying special tools I may only use once or twice for a job. So, I went caveman-style, and used my 8-mil punch to spin the cage inserts out. Worked well enough and I didn't mangle anything, so that's a success. 

You can buy these from any big-box hardware store and you will need them. I've used almost all the punches and have absolutely used the cold chisels. Whether it's for acting as a heavy wedge to split or pry something, or to drill and split nuts that won't come off (looking at you, Whitworth fasteners holding on the stub axles.) You can use them to mark metal objects (like bearing caps!) or drive out split pins that are stuck (like on all the pinion nuts!) 

Well worth having.