Monday, April 02, 2007

Tired penguin

I spent all weekend putting in an Aussie Locker in the front Dana D30 axle of my Jeep. It all went pretty much according to the install write-up, except for one thing: my carrier wouldn't come out.

The carrier on a Dana D30 has a taper bearing pressed onto each end. Now, for those not in the know, these things need preload to operate properly. But there's no space in the teensy Dana D30 case for a preload adjuster. So they're shimmed to use the actual width of the carrier and bearing assembly as the "preload", i.e., the carrier assembly is actually wider than the case. Now, it's not a *lot* of preload. But these are new bearings, so it was enough preload that the carrier simply would not budge when I used the procedure on the install write-up. I spent hours tugging and prying and it wouldn't budge.

Solution: A trip to the hardware store the next morning to get a couple of bigger prybars and an 11/16" closed-end wrench to use as a chock on the ring gear (by putting it on one of the ring gear bolts then rotating until it hit the case, I didn't have an 11/16" closed-end wrench because this is the first car I've had in ten years that wasn't all-metric and 10 years ago I had access to my Dad's toolbox which is now in my brother's possession). Only problem is that my Jeep is up on jackstands with its innards hanging out (the brake disks drooping from where I'd pulled the axles out sure looked hilarious!). Did you know that you can carry a 4' prybar on a KLR650 motorcycle by pushing the seat foam down and shoving it under the luggage rack handles? When the seat foam rebounds, it then locks the prybar in place! As a bonus, cars that try to crowd you get a new paint job (heh!).

Anyhow, the longer prybars did the trick, I put the locker in place of the spider gears and reassembled everything with the help of a 4 pound hammer and a piece of 2x4, I tested the ratcheting and lock-up actions all of which work fine, and all that's left to do now is jack the Jeep back up, kick the jackstands out from underneath it, set it down, torque the lugs (I tightened them but not to 100ft/lbs because doing that while the Jeep is up on jackstands is difficult, that's a lot of torque) and take it for a spin. The only real problem I ran into other than the carrier one is that when I cleaned off the ring gear and carrier to reassemble them (this thing must be meticulously clean, even a spec of sand can throw off the backlash), the brake cleaner and compressed air combined to wash off the marks I'd made for how they're supposed to mate. Ooops! Shoulda used my punch and made a couple of scratches instead! But this is a *heavy* ring gear, and the machining looks very good on both the ring gear and the carrier, so putting it back into the same place isn't quite as critical as with a thinner ring gear though undoubtedly this is going to cause additional wear as the ring and pinion get re-acquainted. Oh well. Can't be helped. I'm going to pop the cover off in a few hundred miles and check the ring gear torques again as well as inspect the locker just to make sure everything looks good, but honestly I don't expect a problem here.

This is a nice tight little differential, excellent workmanship, excellent assembly quality, the bearing preload is just what it needs to be to get the best bearing life, least backlash I've ever encountered from a Detroit differential, before I mucked with it I probably would have gotten 250K+ miles out of it, I probably reduced that to 150K+ miles by moving the ring gear and scuffing the mating surface of the bearing races pulling the carrier out and pushing it back in, oh well... still, I'm quite impressed. Yes, this is primitive 1960's Dana-Spicer technology, but it's done with modern tooling so it's primitive technology done *right* with the best tolerances that modern technology is capable of providing. If only the rest of the Jeep was done to such high standards. As for the Aussie locker... eh. It is what it is, a cheap way to lock the front wheels together while allowing limited differentiation for turns. The only good thing about it is that when the wheels are not being driven, it freely ratchets so it functions as a full differential in that case, making it largely invisible (other than a little noise) in 2 wheel drive mode. But I certainly wouldn't put one in the back of my Jeep. The Trak-Lock limited-slip back there has *much* better pavement manners...

- Badtux the Greasy-flippered Penguin


  1. Geeze - I love technobabble! If I understood half of that I'd feel a lot smarter, but I'm glad you're improving that OEM error.

  2. Not an OEM error, just an option error, as in, I didn't get the Rubicon option (which option adds lockers front and rear) since I was buying a leftover 2006 Jeep and thus was limited to what was actually on the lot.

    I'm sure Da Fixer will be laugh if you call his argot "technobabble", heh! Can it be technobabble if it's coming out of the mouths of grease-stained mechanics with their hands deep in an engine (or differential, in this case)? BTW, by the time I got everything reassembled, my clothes were so filthy that when I leaned against my bed, I left smudges on the sheets. Eep! Need to run another washerload of clothes when I get home!

    - Badtux the Wrenchin' Penguin

  3. It sounds like you put an awful lot of pre-load on the bearings if you needed a pry bar to move it. How did you measure it?

    A rule of thumb is about one pound of friction per inch of the bearing's outside diameter. The way I do it is to set the thing with the play just taken out, no pre-load. Then use a fisherman's scale, attach it to a convenient point, and take note of the reading when the whatever starts to move. Then pre-load by the appropriate means until the increased pound reading is where you want it.

    I hope the thing didn't come with all the shims you would ever be likely to need already in place behind the bearing and you were supposed to remove them as necessary.

  4. Yeah, every idiot needs a Jeep to drive to the grocery store.

    Fuck, I can plow snow with a two wheel drive. Enjoy pissing your money away and thanks for supporting the economy. LOL

    Dana is a little tricky if you want the right bearing preload and gear pattern but on the other hand it is pretty forgiving if it isn't perfect.

    Most drag cars use an Eaton or some other after market if they want something tough.

    Just saying. Hugs from an old race car builder and driver.

  5. Gordon, the preload is actually just fine for big bearings this size, the reason I had trouble getting it started is because of the way the case is shaped. You're really supposed to use a case spreader on this thing, but a) I don't have a lift so I wouldn't have room to use one, and b) I don't have a case spreader anyhow nor any desire to have one.

    I did not actually take the bearings off the carrier. They're pressed on there with a hydraulic press, and you need a hydraulic press to get them off (believe me, many Jeepers have tried to get them off without a hydraulic press, and failed!). So the preload on the bearings is exactly what the Jeep factory intended, and in my experience (admittedly less than yours) appropriate for these bearings. They have enough preload to keep them from being sloppy, but they still move easily and are not in any way flat-spotted or showing signs of stress. All in all, I was quite impressed with the build quality here, especially compared with other parts of the Jeep where the build quality obviously sucked (such as the exhaust system they had to tweak by hand to make it only barely clear the front of the oil pan).

  6. Yeah, BBC, I wouldn't want to actually try to set the preload and pinion depth on this differential. I looked at the procedure in the factory service manual, and checked some other sources who do it for a living and don't live where I live (i.e., they aren't gonna bullshit me just to get my business), and all agree that Dana axles are a pain in the ass to set bearing preload, pinion depth, etc. on. That said, the Dana factory did a damn fine job here. I've seen some Detroit differentials that were just sloppy. This is a tight little differential that was put together right by whoever did it.

    I took the Aussie locker for a little spin. So far so good. It behaved just like it was supposed to behave, quiet and locked up when going straight, clucking quietly to itself when turning as the ratcheting feature allowed it to differentiate. It was literally unnoticable in 2 wheel drive mode. It'll be interesting to see what happens in 4 wheel drive mode...

    BTW, BBC, I had a 2 wheel drive pickup truck and yeah I drove it plenty of places it probably shouldn't have gone. But forest service roads that I could only barely make it over with the pickup are child's play with the Jeep, and there are some things -- such as sand washes -- where I would have never taken the pickup there, and the Jeep has no trouble. And unfortunately many of the roads in our Southwestern deserts require you to go through this deep sand to get where you're going...

  7. This sounds very impressive, and I have no idea what most of it means.

  8. It definitely sounds like more of a chore than setting up wheel bearings or a Sportster swingarm!

    'Technobabble' is fun and cam be used to "baffle 'em with bullshit when you can't dazzle 'em with brilliance". Using terms like 'stoichiometry' instead of 'fuel-air ratio' and 'internal hex lobular fastener' instead of 'Torx' makes folks' eyes glaze over! :)

  9. Also, I spent many years prowling around and racing in the SoCal desert and never needed 4WD, but I was careful where I went and always carried a shovel in my truck. I still do, but it's for snow now.

    I've prowled around our NorCal Forest Service Roads for the last 25 years. I live in the Tahoe NF and the Toiyabe NF is right next door. It's my back yard. I wouldn't go off the main Forest Service roads without 4WD. There are 'designated Jeep trails' I wouldn't attempt with a dirt bike, but the Jeepers love 'em. They'll also hang their buddies' Jeeps from a tree with the winch cable after they've had a coupla drinks! A fun-lovin' bunch!

    Using 4WD is a good environmental practice when driving on any dirt roads. It helps hold down erosion by keeping the wheels from spinning.

    I'd like to see a picture of your Jeep and KLR. Can you get 'em to hold still long enough to get a photo?


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