Tips on Lunchbox Locker install

samedi 22 août 2015

I finished installing a Spartan locker in the Dana 30 at the front of my 99 TJ today, thanks in part to a lot of information gleaned from this site and others. A search will turn up many full descriptions of the installation process, so I thought I'd not post another long DIY tutorial, but instead just post a few things I learned along the way.

1. Use air tools whenever possible for disassembly - with an impact wrench and an air ratchet, I was able to pretty much take everything apart, from brake calipers to carrier bolts. It made the disassembly go really pretty fast. Taking out diff the top cover bolts required use of an extension and swivel joint.

2. I have 3.73 gears, so needed to pull the carrier to install the locker. The carrier was pretty tight, but I used the "shop towel in the pinion" method suggested here. That really pushed the carrier forward. The non-ring gear side was still a little stuck, so I wrapped a ratchet strap around it, hooked to a front tow hook, and it nudged right out. I had to do that again on reassembly, when I didn't line the carrier up right and had to pull it back out.

3. Upon inspecting the carrier on removal, I notices that one of the carrier bearings was bad, so decided to replace them both. I bought the Harbor Freight large bearing splitter, but really couldn't use it without messing up the shims, which I planned to reuse. It didn't really fit that well anyway.

So I used a cutoff wheel to cut the bearing cage off and used the larger splitter in the HF kit to grab the top of the inner race. Make sure the splitter is on really tight - I cranked on it a bit with regular wrenches, but it took my impact wrench to hold it on tight enough to be able to crank the race off with the kit.

I couldn't figure out how to use my hydraulic press to push out the bearings unless I welded up some new tooling for the press - but the kit worked okay. The threaded rods, etc. in the HF kit are really soft metal - bent them up pretty good. I'll eventually replace them with Grade 8 fasteners.

I used the discarded inner races to protect the new bearings when I pressed them on with the shop press.

4. Oddly enough the carrier pin supplied with the Spartan kit was a couple thousandths too big in diameter to fit my carrier. I reused the old one, which appeared to be in perfect shape.

5. When assembling everything (locker, bearings, etc.) I just lubed everything up with the same gear oil I will use in the differential. I've seen suggestions to use various types of grease to hold parts together, but this doesn't make a lot of sense to me: the grease will prevent the gear oil from getting into the surfaces it's supposed to lubricate.

6. It seems like there's a lot of conflicting info on the torque spec for the ring gear bolts. I went with the 70-90 spec. Bought new bolts, cleaned everything well with brake parts cleaner, and used red Loctite. I torqued then up in 10 ft./lb increments and stopped at 75 ft./lbs. I had no issues, no stretching, etc. Just took my time and tightened cautiously. This seems like a better torque value than the 55 ft./lbs I've seen elsewhere.

7. When placing the carrier back in the housing, just take the time to keep the outer races aligned, and make sure the carrier is aligned vertically. I got my carrier misaligned and tried to drive it into place - didn't work. I pulled it back out (ratchet strap and shop rag again) and got everything lined up and it pretty much fell into place with some convincing with a dead-blow hammer.

I've seen it mentioned that you shouldn't try to draw the carrier into place using the cap bolts, so I avoided that - tapped it mostly into place with the hammer.

BTW - I've seen instructions that tell you to cover the newly-installed carrier with a rag, and then clean off the RTV on the mating surfaces of the cover and diff casing. Made a lot more sense to me to clean everything up when the carrier was out. Less chance for crumbs of foreign stuff to fall into the diff and contaminate it.

8. I just reused my carrier bearing shims with the new bearings. I measured the total thickness of the assembly using my granite block and digital height gage, and with the new bearings it was maybe a thousandth thicker than original. After I put everything back together, I didn't actually measure backlash with a dial gage, but it appeared to me to be just slightly less backlash than before.

After buttoning it all up, testing, and refilling with oil (one of those cheap quart bottle pumps is definitely worth the tiny investment) I took it for a spin. I backed up, then had to make a tight left turn, which resulted in a loud bang. Turns out this is not unexpected - and it didn't repeat after quite a bit of driving on our paved and gravel roads. It was definitely different driving with the front end in gear - gripped the gravel with much more authority and, though it was a tiny bit more effort to steer, wasn't a big deal at all.

For anyone thinking about doing this, go for it! I hadn't poked around in a diff or gearbox before, but found this pretty straightforward - just read the tutorials here and watch some YouTube videos and you'll be good to go.


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Tips on Lunchbox Locker install

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