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differential help

Old 11-24-2016, 10:05 AM
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Unhappy differential help

hello I have a 97 jeep grand Cherokee limited. has dana 30 front. the AXLE YOKE that holds the ball joint went outta-round thus the WHOLE ball joint assembly was moving up and down, not safe. so I found a replacement used dana 30. (we will call the replacement axle B) the differential in my original axle (A) is good so I want to put it into (axle B) my issue is that axle (A) differential has NO SHIMS. axle (B) differential HAS shims. so where iam using differential (A) and putting it into axle (B) do I use shims or not? and should I use the complete assembly from axle (A) because the bearings are all good same with races etc. I know this sounds a bit confussing and iam sorry for that ill add pictures
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Old 11-24-2016, 10:49 AM
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first off, you cannot just pull the carrier with ring gear out of one axle and put it into another. you need to set up the gears properly or you will just burn them up.

your best bet is to swap complete axle housing with original internals into the jeep, as long as the gear ratio is the same as your original axle assembly.
there are some differences between 89/90 and 99/00 that you may need to be aware of. 89/90 has different brake caliper mounting and 99/00 went from high pinion to low pinion.
then it's not as important, but 94/95 went from smaller 260 u-joints to larger 297 joints.

as for "ball joint", i'm not quite sure what you are referring to. a ball joint is what the outer knuckle turns on where it is attached to the axle housing.
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Old 11-24-2016, 02:49 PM
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Welcome to CF!

Also, The 99-04 has a wider thread width, axle flange to axle flange. The wheel bolt pattern is 5x5 rather than your 5x4.5, and even the spring seats may be farther apart, IDK. SO, the newest axle you'll be able to put under that is a 98. The main difference between the high and low pinion axles is the high pinion is a tiny bit stronger and adds more ground clearance to the driveshaft. It was mainly used in XJs and TJs.

Setting up the proper pinion preload and ring gear backlash is something best left to the professionals. A differential is the most important part of any vehicle and least understood by the average owner. If you don't have a dedicated 4x4 shop in your neighborhood, a heavy truck shop can usually do it for you, OR you can get your wallet cleaned out by the dealer.

If it were mine, I'd get axle "B" checked out by a shop to make sure it's okay, then swap it in. It goes without saying, the axle ratio MUST MATCH the one you already have in the jeep! If axle "B" isn't the same ratio, you're going to have to have the pinion and carrier assembly from axle "A" installed and set-up in axle "B" or at least used the ring&pinion.

If they are different pinion heights, that limits your options.

Last edited by dave1123; 11-24-2016 at 02:59 PM.
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Old 11-25-2016, 10:19 AM
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allow me to try to clarify this axle A's ring/pinion/bearings are all GOOD. they are gonna go INTO the replacement axle called axle B. which is ALSO from a 97 zj. the differential that was in the replacement axle is shot, however it has shims. axle A's differential (the good one) didn't have any shims. and when I put the good differential in the replacement axle I have only 0.001" of backlash if I try putting in shims I have 0.000 backlash. I know jeep calls for between 0.005-0.007 of backlash. how can I increase backlash if shims wont fit??? should I use the bearings (which have shims) from the SHOT differential???
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Old 11-25-2016, 03:22 PM
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You see? This is where you need professional help. The pinion may need to be set deeper into the case to give you more leeway in setting the backlash. The specified backlash is to allow for thermal expansion of the gears when under power. Zero backlash will overload the pinion bearing in short order. IMHO, even .001 is too tight.
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Old 11-25-2016, 10:01 PM
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Have you checked the contact pattern first ?That alone will let you know if you got a pinion right or not.And take a look at https://www.powernationtv.com/episod...diy-axle-setup
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Old 11-27-2016, 01:24 PM
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reply to dave1123 ; I went to community college for automotive and completed the program, so I do have some training in doing this, in a "school environment" as we all know its WAYYYY different from the real world. so I do understand the process. I have the pinion able to rotate at the(what I believe is spec 35 IN LBS, from what jeep told me) and the cap bolts are torqued to 60 FT LBS per spec. I haven't done the contact pattern YET, because I don't have ANY backlash. which I know is NOOOOO good. I tried using shims and I know they go in tight. but I CANNOT get the differential to fit in the housing (case) if I put even one shim in. and I know to increase backlash it needs to go on the right. so I am wondering are all the bearing races (the round piece that goes over the carrier bearings) are those all the same dimentions for the dana 30? or are the different sized like the shims would be. I aske because the shot differential that was originally in this good salvaged dana 30 housing HAD shims. but my stock dana 30 DIDN'T have shims. I am trying to do this myself to save money. I havee dumbed soooo much into this jeep just trying to do this whole project already that I cant afford to spend more. I have the tools and specialty tools needed to do this job, so that's also why I am trying to do it myself.
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Old 11-27-2016, 04:28 PM
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I am, by no means, an engineer or driveline specialist, but I AM a toolmaker and I know all bearings are manufactured to pretty strictly held tolerances but DO have differences in dimensions when assembled. I also know that the aluminum case D44a must be "spread" to properly preload the carrier bearings. I don't think the steel D30 or D35 can be spread or need to be, but there is a free rotational torque limit that must be held just as the pinion has.

What I AM saying is setting the pinion .005 or .010 deeper may give you the backlash you need without changing the contact pattern too much. This is where experience becomes necessary.

My only actually differential experience is with a heavy-duty GM 12-bolt Posi unit in my 67 Camaro when I blew the carrier cross-shaft. That had heavy shims on both sides of the carrier. When I put it back together, I switched the two shims, bringing the backlash back to where it should be from wear caused by drag racing it. I don't remember the sizes, but these were factory ground spacers rather than shims.
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Old 11-28-2016, 07:57 AM
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To Wobbles. You'll probably find the shims UNDER the carrier bearings. I recently replaced my D30 carrier bearings and the shims were under the bearings on mine.
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