Replace bearing or re gear?

Not sure if this should be OEM or Modified... but here goes nothing.

I have a '91 XJ on a 6" homebuilt lift with 33" M/Ts (4.0 and NP231). I also have the coveted (so I've heard) High Pinion Dana 30. F/R gears are only 3.55. I have an Aussie locker in the front and have already exploded the short shaft once, had to fix that with the spare on the trail.

Well, I have a lot of play in the pinion up front, i mean A LOT, leading me to believe that a pinion bearing replacement is needed. What should I do?

Option 1: Replace the bearing... How hard is that? Can I do it on my own with air tools and a few other cool things (I've replaced input shaft on 231 myself and installed the Aussie...)?

Or, option 2: I bite the bullet and re-gear... This would most likely render my Aussie useless since I'll need a new carrier (i think) and I would also have to find an 8.8 or other axle to replace the d35, then i need to do SYE (yea, I haven't done that yet... and it would be necessary with the slightly off center 8.8" pumpkin) because there is no way I would spend money to regear the garbage d35 out back.

So it really comes down to this question: Is it difficult to fix the pinion slop for a few bucks and some elbow grease? Or should I go ahead and do the rest (stuff that I plan on doing, just not right at the moment)?

Thanks for the input!

I am pretty sure that replacing the pinion bearing will require setting gears all over, so either way is the same amount of work, just different money

If the diff has been run for any significant period of time with a bad pinion bearing it may have worn the gears strangely anyways (the worse the bearing gets, the shorter a time it takes), at which point you may as well just regear.

If you catch it early and especially if it's just the outer bearing that went bad, you can slap another in it and run it for a bit longer. Expect to need a new seal and a new pinion nut (a few bucks online) as well. Don't expect it to have a perfect contact pattern or pinion preload unless you really know what you're doing and dig into it, and if it needs a new inner bearing as well, you're going to be in there pretty damn deep.

I'd probably slap a new bearing/seal/pinion nut on it for now, grab another d30 (any 80s through 99 XJ has a high pinion, not that coveted, any 95 through 99 has one of the best-optioned ones with larger shafts) and whatever rearend you want, regear them, then swap them in. Zero downtime!

If you go over 3.55 gears in a d30 you do need a new carrier, but the aussie will fit it, so you can just swap that into the new carrier. The only difference between the 3.55/down and 3.73/up carriers is the position of the ring gear mounting flange on it, the inside dimensions and carrier bearing dimensions are all the same.

Junkyard shopping list - 95-99 dana 30 from an XJ, diff carrier only from a ZJ with 3.73 gears (probably any V8, but double check ratio tag before buying), and either a 95+ 8.8 or 97+ 8.25 depending on your personal preference. What gears are you thinking? 4.10 I'd aim for an 8.8 since they can be found with them from the factory, anything past that, it's 100% your call.

The reason to get the diff carrier from a ZJ d30 is that they often have 3.73 gearing in the V8 vehicles - it's a low pinion d30, but the carrier is the same low vs high pinion, so finding one with a V8 and 3.73s just means you can buy a cheap junkyard diff carrier instead of an expensive new one. ECGS wants $64 for a 3.73/up d30 carrier, so if you can find a junkyard selling diff carriers for less than that, you win.

Regear to 4.10 since you have a manual tranny.
Your Aussie will fit in the 3.73 and up carrier.

Great time to upgrade to a full case locker(s) if you're so inclined.

I never thought about that with the ZJ!! Thank you! I think i'll be getting that and looking for the 8.8. What's stronger in the newer d39? Is it a higher spline count? I guess I could look around for that too. It's a shame my 30 gallon air compressor would be such a pain to lug around in the upullit lots.... I appreciate the help guys! The good news about my current set up is it's not my dd and was sitting for about 5 years in my dad's driveway before I got to haul it down to FL.

I have a lot of play in the pinion up front, i mean A LOT,

Click to expand...

Do you mean up / down / in / out type play or rotational play / backlash ?

If the latter, most of that is from your Aussie, nature of the beast.

This depends on what kind of play you have. If the pinion moves up and down when you grab the yoke, that is radial play and it indicates a bad bearing. If the pinion moves in and out when you grab the yoke, that indicates axial play and also indicates a worn out bearing. If the play you have is rotational play, it is perfectly normal for a differential with a lunchbox locker. As long as it is not like a half turn or something you are fine. If the pinion bearing is in fact worn out you may be able to replace the bearings and bearing races without redoing the gear setup. You will have to run a pattern after replacing the parts and see if it is in spec. I suggest replacing the carrier bearings as well. Check the backlash before disassembly and if the backlash after replacing the parts is close (within about .002") and in spec you should be OK. If the wear on the ring and pinion is noticable you should probably replace them.

Looks like the decision has been made for me and I'll be going with Option 2!

So...... May not have just been my pinion bearing... opened up the diff cover tonight to reveal an exploded carrier bearing!! Luckily, it looks like my Aussie Locker seems to be in tact still... Let the hunt begin for a new d30!! Any recommendations on yards in orlando??

Carrier and gears are both toast. I recommend a good aftermarket carrier because the stock carrier is weak with a lunchbox locker.