Hello all I have a question conserning differentials. I believe I have a 30 and the gears are 3.07 and I just recently had a pinion bearing failure. Well anyways I was gonna change up the gears to either 3.73 or 4.10 I'm running 33 tires and the seller said that I would need to get new carriers (?? or those same as spider gear housings) along with new gears. Is this true and which gears do you suggest this being my primary mode of transportation. thanks for any info  

Need a little more info.  If you have the 6 cyl engine; with 33s you would be happier with 4.10s.  Even more so if you are going to wheel your Jeep any.  The 3.73s would be fine, but you will want more gearing later down the road if/when you go to bigger tires.  If you have a 4 cyl, then I would step up and go with 4.56s or 4.88s.  Those 4 cylinders need all the help they can get.

Yes, you will need a different carrier.  Dana 30s, 35s, and 44s have a carrier break at 3.73.  What that means is that if you have 3.73 and numerically lower (your 3.07s) thicker ring gears (4.10s) will bolt on, but your pinion will not engage correctly with the ring gear.  You can buy an empty carrier and then move your spider gears and cross-pin over with no problems.  

That jeep did not have proper axle ratios when it was built as they were too tall then and they made it that way to look a fraction better on EPA MPG test. (BTW. 3.07 was standard with a 6) A 3.73 would not be wise here and with 33's it is tall too. You want at least 4.10's and even 4.56 is if you plan to go bigger one day. As far as carrier issues, yes there is a carrier break at 3.54/3.73 on front axle and 3.31/3.54 on rear axle.  

Hey thanks alot for that info. My jeep has a 6 cyl. You know I'll probably try for new carrier housings and just transfer spider gears as for tires I'm happy with the 33's and I'll most likely run 4.10's being I'm a beginer off roader. thanks for all your help and advise.  

IF you stay would stock open diffs you should have no trouble finding some used carriers. ALso if you wanted to upgrade to a LSD type diff, now would be the time to do it when you change gears.  

Yea, Sno is right. If you have the money now is the time to install a locker or LS... no reason to pay for the labor twice.  

Yeah I would love to do the LSD upgrade but I'm limited on funds. The kit that I'm looking at will set me back 498 bones and thats not including labor and its just the rears. Which leads me to another question do model 35 gears fit in model 30 gears I'm just shoppin around tryin to put together parts.  

Where are you pricing gears at and what kit??? You should be able to get new gears for both axles for about 300 to 350 total and another 300 to 400 for a rear LSD plus maybe 50 to 75 for a used carrier for front axle. Also if your axles are running quiet now there is no need to change all the bearings in them. (especailly in front axle) Generally they (bearings) fail because axles are not serviced regularly and properly or the were setup up wrong when axle was built (wrong preload). Keep fluid fresh and full and they will last a long time.  

Well I got the quote from 4wheelparts and that is for rear 4.10 gears, repack bearings & seals kit, and spider gear housing. I need new bearings and seals for rear thats the primary cause of failure in first place. Water must have intruded when I went through river. So are model 35 diff gears compatable with model 30 differential? Thanks for help.  

D30 and D35 gears are not interchangeable at all. Different carrier break, different ring gear diameter and different ring gear bolt pattern too so it is not even accidentally possible.  

Thanks again. I have another issue, it seems that my jeep wants to give out on me. I should expect it thow after 2000 ml round trip. Anyways my oil pres which is normaly around 43 psi in all ranges from idle to 2000 rpm is now at 47 when going about 30 mph and climbs as high as 77 when I increase speed to around 55. After about 10 minutes of driving pres decreases back to around 47 at 55 mph. Any guidance will be apreciated I changed the oil and filter but that shouldn't have to do with high oil pres would it. Also I am running in fwd being my rear dif is inop. engine 4.0, 6 cyl 107,000 mls Thanks.  

What grade and weight of oil are you running? Also oil pressure will be higher until it warms up completely and in winter. I have a old Jeep J20 with a V8 and when it was "younger" it would pass 80 PSI when cold on the road  until it warmed up and dropped back to 55 to 60. (now it hits maybe 70 cold and 40 to 45 warm). ALso during the life of a oil change it is normal for pressure to drop some as oil breaks down and filter starts to fill up. BTW, 35 to 40 PSI or better at 55 is quite safe on that engine so at 47 you have no worries. When it gets below the range mentioned above then you need to look into it further. As far as idle pressure, anything above 25 PSI or so on a hot engine is fine.  Grade/type of oil has a big effect on oil pressure at times too.  

I gotta add a Question..........manual or automatic?

I'm assuming it's auto, if it's a ax-15 manual, forget the 4:10's and use at least 4:56's, even the 4:88's in 5th, will still turn 200rpm less than the auto with 4:10's  

While I am not sure, I believe that the automatic has a taller OD ratio than the AX15 which only has a OD ratio of .78 to one. My guess is that it is around .75 on the automatic which was commonplace with Chrysler trannies of that era.  

97-02 tj's have a 32rh 3 spd,

the aw-4 (xj cherokees)is .69 and has a 2.80 1st.