Time for 4.10 gears!

JeepJeepster · Sep 26, 2020

This is something I've wanted to do since I found out 4.10 gears existed for the KJ. With the hilly terrain in this area, the KJ has always seemed under powered. After putting the 245/70/16 tires on and all of the extra weight from skids, subwooder, and whatever else I normally have in the Jeep, it struggles to maintain the speed limit. If you use cruise control it constantly unlocks the torque converter and/or downshifts. It had gotten to where I dreaded driving it. My 94 with the 4.0 has more low end torque and just cruises on the interstate, so I put a cover on the KJ and let it sit for most of the year. Recently decided to drive it again and Im finally fed up, shes getting 4.10 gears and a detroit truetrac!

Ordered the gears and master install kits from Just Differentials. Nitro rear gears, dana front gears, and USA Koyo bearings. They told me they only had 2 sets of dana gears in stock when I ordered these but it also appears you can order yukon gears on amazon. The truetrac came from drivetrain american since JD didnt have them in stock and I found it cheaper than what they had it listed for anyway.

I ordered the tool for setting carrier bearing preload in the 8.25 from amazon for $25, it wasnt worth making a tool for $25 shipped. Also ordered a timken inner pinon bearing (couldnt find the koyo bearing by itself? We'll see if the timken works) to make a setup bearing, it appears the two diff's take the same inner bearing. Ive read you must use the same brand, I'll see if the timken sits in the race the same depth as the koyo. Im assuming the Jeep has timken in it and when I ordered the master kits, I didnt realize you needed the same brand to make a setup bearing nor did I know I wouldnt be able to find a single koyo pinon bearing. If I had I wouldve bought master kits that used timken bearings.

I've been doing ALOT of reading and watching lots of videos. Gear work is something people always say to leave to the pro's but Ive yet to meet a pro, so its up to me I suppose. I've read several different methods. One method involves a pinion bearing depth gauge. They are rather $$ but Im ok spending money to do things perfect. After getting the dana30a gears I realized that wont work as the head of the pinon bearing isnt flat nor does it have the pinion depth measurement on it. I could measure the stock pinion depth since its also dana, but again, the head isnt flat so I have some more research to do on that. The nitro gears for the 8.25 do have the measurement written on them and the pinion head is flat, but Im not spending almost $500 if the tool only works on the 8.25. So Im just going to make a setup bearing and do it the hard way. Put the original shim in there, set it all up, adjust the backlash, and repeat after checking the pattern. The FSM has very good photos that tell you what to do depending on how the pattern looks. I wish the dana30a had the same side adjusters like the 8.25...

Still have some parts coming on monday but I figured I would get started on it today. Kinda thought I had a ujoint going bad as it had some vibrations when I could get it to go over 70mph (going downhill of course)... The ujoint on the axle end was very tight, but the cups still had grease in them. Originally it had a spicer 1310 in it, so I ordered a spicer. I was able to get one side to move with a hammer and socket, but the other half needed the press.

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If anyone from the old days is still around and remembers, I always had a cat working on my Jeep with me. He died many years ago, but this cat showed up awhile back and oddly looks like my old cat and likes to hang out in the garage as long as Im not making loud noises. She said the diff oil stunk

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Here you can see the numbers written on the 8.25 gear. When I ordered the gears from JD, the guy said the gears would be marked with a -0.000 number or a +0.000 number. He said thats how much you either add or subtract from the original pinion shim thickness. I'm wondering if the 0.006 is the number he was talking about, but I dont believe I can change the shim thickness by 0.006"... If I were using the pinon depth gauge, 2.373 would be the measurement I would use to figure out what thickness of shim to use. Thats the distance from the center of the ring gear to the face of the pinion gear, this is also the measurement that is not on the dana30a gear. It has neither measurement but it does have a Q0 and H3 on the head, idk what that means just yet.

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More to come later...

tommudd · Sep 26, 2020

Good job so far, and yes I do remember your cat always being under the KJ with you !!
Good luck, get them broke in right and you'll enjoy driving the KJ again

profdlp · Sep 26, 2020

That looks like a big undertaking and a whole lot of fun.

HoosierJeeper · Sep 27, 2020

Good to see you back! I want to do this to mine too.... eventually... gotta get the Rene beefed up tho.

lfhoward · Sep 27, 2020

Same here, would love to have 4.10’s. Going to watch and learn as you do them yourself. Good luck!

JeepJeepster · Sep 27, 2020

What a long day... I imagine I have over 6 hours in this and Im no where near done. At this point, I'm not sure you could pay me to do this. The Jeep did have timken bearings in it from the factory. All of them said timken except the inner pinion bearing, it has nothing on it but the race has timken on it. I really wish I wouldve waited to get the install kit so I wouldve known what brand bearings to get.... I'm not sure why install kits dont include a setup bearing... That would be super handy.

An air hammer made quick work of removing the old ring gear and popping the tone ring off. Even though the TT was frozen solid in the freezer and I got the tone ring nice and warm, I could not get it on without using the ring gear to press it on, really didnt want to do that but I didnt see a way around it. The ring gear fell right on after heating it up. Unfortunately I stripped every single bolt for the new ring gear.... The nitro ring gear has two sets of bolt holes in it and in my ignorance, I didnt notice the threads in one set of holes are SLIGHTLY different. I figured one set of holes was for a different carrier or something and the spacing must be a little differenet. So when the holes lined up, I thought I had the correct set of holes. Was torquing them down and they got to 40 lbft, set it to 75 lbft and they weren't getting any tighter.... Took one out and yep, threads were gone. Took me a bit to figure out what was going on b/c again, even after removing the ring gear I couldnt tell a difference in the threads... Idk why they would do that, just seems like theyre setting someone up. Anyway, ordered some ARP bolts and I'll just swap them out. Used the old bolts so I could get it in.

The TT is very heavy, much heavier than the stock carrier. It was a battle getting the TT in, holding the races, and trying to get the side adjusters in while making sure the threads were all straight on the adjusters. It would be much easier if the Jeep was on a lift. Be very careful not to tighten the cap bolts till you know for sure the side adjusters are all lined up. If you mess up the threads for the side adjusters, well, you'll be getting a new axle. I couldnt find where the FSM addresses what the original torque should be on the main caps. It says to install them, set the backlash, then torque the main caps followed by torquing the side adjusters. I'll let you know if I still think the side adjusters are better than shims after I get the front diff setup....

I used the shim that was under the original pinion since I wasnt sure what the 0.006 meant on the ring gear. Everything I read said that it should have a - or a + by it which tells you what to add or subtract from the original shim... So I bought a timken bearing, ground it out, and used it as a setup bearing. I set the backlash as per the FSM and wouldnt you know it, the pattern is better than it was originally. Its 100% dead center for both the drive and coast side. Hopefully when I remove the timken setup bearing and put the koyo bearing in it wont screw everything up. If it does I'm not sure what I'll do just yet....

Original pattern. Im not sure I would be satisfied with that if thats how my pattern looked. The backlash was 0.010 before I removed everything, Ive got it set to 0.004 right now but thee FSM wants 0.006-0.008. I'll try 0.006 once I get the koyo pinion bearing in to see how that looks.

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Pattern after installing everything:

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tommudd · Sep 27, 2020

Good job so far
Taking it slow and easy is the way to go
If you have never done it and then its still a crap shot at times
I used to do gears all the time in a dealership, but that was over 35 years ago
any more let the guys that do it daily do it if I need any done
Don't have the time or patience

JeepJeepster · Sep 28, 2020

Another long evening. Let me tell you, Ive heard that it takes a lot of torque to crush a new crush sleeve but thats 110% an understatement! The FSM states that you must torque the new crush sleeve/pinion nut to 210 lbft then check rotating torque. At 210 lbft there was still tons of play in the pinion, I inched up to 250 lbft which is the max on my torque wrench and it still had play in it. If I had a good long ratcheting breaker bar this wouldnt have been too bad but I only have a 15" breaker bar and a long breaker bar from horrible freight. Idk what size the new pinon nut is but all I had that it would fit was a 32mm and it fit very tight, had to hammer it on and back off. So I spent 2 hours trying to get breaker bars arranged while using a floor jack to jack on the breaker bar to crush the sleeve. Idk how much torque was on it, but that breaker bar had some seriously bowing going on, I thought for sure it was going to snap. The FSM states for new bearings you want 10-30 inlbs of rotating torque and I stopped at 20, it was going up quick at that point and I sure didnt want to pass it up.

After getting the koyo bearings pressed on and getting the pinion setup it didnt take long to get the carrier back in. If you read the procedure in the FSM for setting the side adjusters this will make sense, but I found I had to initially set the backlash just a hair less than 0.003" then when I did the 75 lbft torque the back lash was right on 0.007. FSM says you want 0.006-0.008 so Im good with that. I kinda like being on the low end of things b/c I feel like its going to wear and increase. Factory was 0.010". The mesh still appears to be perfect! If the mesh wouldve required the pinion depth to be changed after pressing on the bearing and putting the seal in, I was going to have to take a few days off. That wouldve been pretty depressing to have to buy another install kit, but I was going to buy timken so that wouldnt happen again. So in my case, using koyo bearings and a timken setup bearing worked fine. I can see how things would go south quick if you had to keep taking the carrier out+pinion out to adjust the pinion depth.

Dont really have any new photos. I also got the ujoint replaced on the driveshaft and put it back in the tcase. The new ring bolts are coming to tomorrow so I'll replace those. New axle bearings wont be here till later this week. I was debating not replacing them but after pushing that side adjuster tool in and out 50 times, I thought it would be best to replace the seal and if Im doing that, I'll replace the bearing too. Hopefully I'll be able to take it for a test drive this week sometime. Gotta read up on how you break in gears.

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The coast side might have moved towards the toe a little but the patterns still look much better than the factory gear did.

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Hopefully it never needs to come back out:

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lfhoward · Sep 28, 2020

Wow, man. Impressed. Also I will probably never do this job myself after seeing what you had to do. Lol.

I’m looking forward to hearing about how driving it has changed though.

JeepJeepster · Sep 28, 2020

Checked what the rpm's will be with the new gears. A 2002 liberty with the 45rfe transmission has a 4th gear ratio of 0.75 while the 42rle is 0.69. At 60mph with the factory 29" tire, the rpms would be 1,945rpms with the 45rfe. With the 245/70/16 tires and the 42rle, the rpms will be at 1,933.... So the rpm's will actually be less with the 4.10's when compared to a factory 2002 liberty... I was hoping I would have a little extra rpms but I guess not.

Wonder if the mpg on the window sticker changed? Just not sure what the reason is for the 0.69 ratio since the 42rle was used in jeeps and trucks. Seems like a horrible idea.

JeepJeepster · Sep 30, 2020

Rear diff is done and I took it for a drive this evening. Ordered the wheel bearings/seals on monday from rockauto (mopar) and they still haven't shipped. Couldnt wait any longer, maybe I'll change them out at the 500mi oil change. So far its nice and quiet, no whining or noises. The vibration seems to be gone so I guess the ujoint was causing it.

I'm not sure that it made as much of a difference as I was expecting. You can certainly tell a difference and it doesn't seem to constantly be lugging. When the torque locks up at 45mph it would usually immediately unlock to gain speed, but now it seems to be able to actually speed up and stay locked. When the torque unlocks going up hills it is able to maintain speed and maybe actually speed up a little. I went up a hill where it previously would drop below 50mph in 3rd (its a big hill) and it was able to hold 55mph. I was hoping it would be able to hold 60 but no dice. Overall I feel like it just drives like it should and nothing more. I only briefly got it up to 75mph and you can certainly tell the rpms are higher.

If anyone is wondering about cost...

-Nitro 8.25 gears C8.25-410-NG $315
-Nitro 8.25 install kit (koyo bearings) MKC8.25-B $111
-Dana 30a dana spicer gears D30KJ-410LIB-OE $468
-Nitro dana30a install kit (koyo bearings) MKD30-KJ $151
-Detriot Truetrac $664
-Extra Timken inner pinion bearing for setup M802048: $16
-Dial Gauge TR7020 $46
-ARP ring gear bolts 2403001 $46
-Mopar Axle bearings/seals $100

Total: $1,917.... And thats installing it myself and already having other tools that you need.... Wish I had the know how and money to do this 14 years ago...

I suppose one nice thing about having the tone ring on the ring gear is the speed-o is still correct....

JeepJeepster · Oct 11, 2020

Started on the front last night. Its not too bad getting the front diff out and it makes it much easier working having the diff on the table instead of under the Jeep. I did have to remove one of the lower control arm bolts since jeep likes to put bolts in backwards so you cant get them out. There mustve been a highly disgruntled employee at chrysler that enjoyed screwing with people by putting bolts in backwards. I marked the cam bolt as well as I could but I think it was pretty much bottomed out in full adjustment anyway.

The backlash was 0.009" and the pattern looked 'ok' on the stock gears. For whatever reason, the nitro kit has two different sets of shims in it but neither are the correct shims for the carrier. The pattern is still ok but I feel it could be more centered if I had some shims to move it around some. The stock shims are both very thick (cant remember the thickness) and they are both the same thickness, so swapping those wont do anything. I did add 0.003 behind the pinion bearing and that didnt do much but it did tighten the backlash up a bit. I think I'll take it back and and just let it go... It was working fine before...

Something is leaking pretty good on the steering rack. Ive not looked at it yet but it looks like it may where the hoses hook up to the rack, hard to tell. It does look like a bushing is going bad so I just ordered some new mopar bushings. Guess I'll take the rack out.

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Factory pattern:

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New gears(0.008" backlash, range is 0.005-0.008"):

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After adding 0.003" behind the pinion bearing.

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I think I'll take the shim back out... Now I wish it just had side adjusters, that would be much easier.

Ive not tried replacing the axle seals yet but I think I'll try to just leave the bearings. They appear fine. The kit did come with new bearings so we'll see.

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Call me stupid but I didnt think about the housing be aluminium... Had some steel on hand that I could put the dial on. I must say, this housing is very weak looking, no wonder they crack. I feel kinda dumb putting $$ into something thats so fragile. The bearing caps are aluminium theyre so light you can hardly feel them.

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tommudd · Oct 11, 2020

I can't believe that you didn't notice more of a difference
of course most of the time the ones we do here already have much larger tires and running like a real dog

JeepJeepster · Oct 11, 2020

I too thought it would make a huge difference since I just have the 245/70 tires. Dont get me wrong, it makes a noticeable difference, just not as much as I thought it would. I think it could easily use 4.56 gears with bigger tires.

tommudd · Oct 12, 2020

I always wanted 4.56s with 32s on the 04, but never got the coin together when JBA had them, so its stuck with 4.10s
the 03 with 31s ( 265-70-16s ) and 4.10s does really good overall for me

JeepJeepster · Oct 12, 2020

I too wish I would've gotten in on the front diff's Tom, such a shame.

Got a little more work done on it today but only worked on it for maybe an hour. Maybe someone else can do it, but I couldnt get the axle seals out without damaging the bearings. Went to autozone and rented a pilot bearing puller and popped the bearings right out. The puller scored the surface pretty good so I had to use a file to smooth it out, so be careful when pulling them. I didnt think I had the pilot bearing puller that tight but I guess I did. If anyone wants the metal bearings and not the plastic junk, they are torrington J228 and it appears you can still buy them.

Anyway, learned something new this evening. I gave 'just differentials' a call after thinking that the carrier shims appeared to be the incorrect size in the kit... Turns out, the carrier shims go behind the carrier bearings.... What a horrible design! So I went from easy to work with side adjusters in the 8.25 to shims BEHIND the carrier bearings in the dana30a.... So if you need to adjust the backlash youve got to remove the bearings and move the shims around... Which means you need to make two setup bearings.

I asked Jared at just differentials if they were ok with me sending them pics of my patterns to see if I needed to mess with pulling the carrier bearings off and adjusting the shims. He said no worries, people do it all of the time. Thought they wouldnt want the liability but they quickly replied and said my patterns looked perfect. Its ok for the coast side to be slightly towards the inside (heel) of the gear. I went ahead and sent my 8.25 pattern also just to verify it was ok.

So I must say, I cant recommend just differentials enough. Jared stayed on the phone with me and answered all of my questions, didnt act like he needed to get off the phone. He did say that sometimes he will measure the old crush sleeve then slightly crush the new crush sleeve in a press so its not so hard to get that initial crush. Just make sure you leave it slightly longer than the old crush sleeve... I may give that a try. He said he only remembered putting 4.10 gears in 2 libertys. Its cool talking to someone that really understands something. I rarely get to talk to someone like that so I have tons of questions when I do.

Something appears to be leaking above the steering rack, or Ive just been dumping oil on the steering rack when taking the oil filter off. The timing cover does have some oil on it, but its not dripping and oil was dripping off the steering rack. Its dark too, not red. I just changed the oil pressure sender and the old one didnt appear to be leaking. I cleaned the steering rack up with brake cleaner so I'll keep an eye on it. Going to change out the orings on the two lines at least. Air hammer made quick work of getting the old bushings out and they dont appear to be bad... O well, new ones will be here this week sometime. Guess my wondering issue may just be the rear upper a-arm.

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These are the two spacers that go on each side of the carrier, not to be confused with shims...

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My garage is a mess....

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JeepJeepster · Oct 24, 2020

Had some things going on so I've let the KJ sit for a couple of weeks. Trying to figure out what to do in life.

Anyway, got back at it today and got it all finished up. The crush sleeve was MUCH easier to crush than the 8.25 was. The pinion holder that I got from bleepin jeep made it easy to hold the pinion but it would still be nice to have a torque multiplier if you did this very often. Bought some bolts for the pinion holder, M8x1.25 if you need some bolts. Set it to 20inlbs, the FSM says 15-25inlbs for new bearings and that feels like a lot when you turn it by hand. Thought for sure I had gone too far.

The old steering rack bushings appeared to be fine but Im glad I replaced them anyway. Much easier to do with the diff out. Coated them in silicone grease and they easily pushed in by hand, torqued the rack to specs. I couldnt find new orings for the steering rack so I had to reuse the old ones, Ill keep an eye on them to see if thats whats leaking now that everything is clean. The high pressure hose that I replaced in 2011 is seeping again, maybe its been dripping some.

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All Done!

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Took it for a drive and left it in full time the entire time. Figured if the gears didnt have a load on them a test drive wouldnt do much good. There is a slight whine above 65mph under very light throttle, which its always had, but it seems a bit louder now. Im assuming that would just be gear noise since under load or when coasting, its completely quiet. I'm going to check the rear gears backlash to make sure theyre still in spec. Not sure what else it could be other than the gears just not being broke in yet. Only have 200 miles on the rear gears.

Hopefully I wont have any more leaks for awhile. Both pinions, the front main seal, and the valve cover gaskets were all leaking and have been replaced.

Anyway, did some camping recently. Weather was simply perfect for camping.

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tommudd · Oct 24, 2020

Good job,
Just make sure you take it easy on them for a while and break them in right
See a couple of KJs where owners got gears installed , never broke them in and then complained about noise, etc

I need a little camper like that , nice !

JeepJeepster · Oct 24, 2020

I'm being as easy on them as I can and I'm only taking short trips. The first trip on the rear gears I drove 20 miles and Im wondering if I should've only done <10miles. The rear diff was ~160F which is pretty hot I think, it was just 130F after driving ~20 miles today. I'll change the oil at 500 miles and go from there.

Yeah I like the camper. Its comfortable yet it still feels like youre camping. After the rona stuff goes away and city folk quit flocking to the camp grounds, I plan on towing the camper to the Smokies with the KJ to do some camping.

mxzla · Jan 18, 2021

Thanks for sharing all of this JeepJeepster I enjoyed reading through your process. How are the gears treating you today? I'm planning to lift my Liberty 2.5" and run 245/75/16s -- and from what I've gathered on this site it wouldn't be entirely necessary to swap the gears out to 4.10, but I really do not want to lose any power. I live in hilly terrain and I love the pick-up I currently have with the stock height and tires.

Also -- any idea how much a shop might charge for this labor? It'd be a fun project but I don't know how feasible it'd be for me to do, with limited tools, experience, and time.

Time for 4.10 gears!

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