Not only that, but the difference between 3.55 and 3.73 is so small, you might make a mistake easily. If you engage in 4wd and move slowly, it will bind within a very short distance if it's different. The best way is to open the horse's mouth and count it's teeth.

 

yes. it is an early xj diff. only up to 92 used this type of axle and only non limited trim without abs packages got this. the vac lines would have went to the transfer case, so when 4wd gear was selected, the vacuum sent to the diff slid the collar over the two ends of the axle shaft.
these axles are both good and bad. the good is the size of the axle shaft, bad is the size of the u-joints. good is the upper control arm mount being solid on that side, bad is the axle tube has a big hole that needs to be covered (with the cad motor) or a block off plate.
guys have pulled the shaft out and installed a one piece shaft, but there is a seal in that axle that needs to be removed to be able to fit the new axle. not a big deal tho. this will keep the solid control arm mount which is much stronger than the stock one on a non CAD axle. then a plate to cover the hole.

i have fought with this type of axle in an xj before. not fun on the trail and the hose clamp got pushed back enough so the collar wasn't engaging both shafts. have to pull the cad motor housing to fix, while in the mud and everyone has to wait on you.
so i pulled that axle assembly and replaced it with a complete unit from my 89 limited parts jeep. other than swapping outer C knuckles so my brake calipers would mount up, it was a good fix that works better than before. even has the bigger u-joints, so that's a bonus. you won't get bigger u-joints unless you swap out to a 95 and up axle otherwise.

but the bonus of having a cad axle is if you wanted to put a locker in, you can install a Posi-Lok cable to essentially "turn on/turn off" an auto locker like an aussie or Lock-Rite, BUT, you would still have the smaller u-joints snapping if bigger than 33 inch tires. (ask me how i know. lol)

as mentioned, gear ratio is stamped on the edge of the large ring gear. it won't be stamped simple as 3.55:1, but rather two numbers, number of teeth in ring gear, and number of teeth on pinion. you would have to do the math to get actual ratio, or look it up on the interwebs. still easier than counting teeth.

just do what i did. swap out the whole axle to a newer (95 to 99) front axle and just be done with it.

 

They quit using the CAD axle in 91 on the XJ.

 

I appreciate everyone's thoughts and ideas on the axle issue. I may do a mix of solutions, I may try to move and lock the collar where it locks the axles together for now and in the near future swap out the whole front axle with one from a 1998 at the local u pull yard.
I am restricted in a lot of what I can do until November by a weight limit imposed on me by my doctor after neck/disk surgery on my neck.....doing too well to screw that back up! The limit is 15 pounds although I had to stretch it a little during Hurricane Laura moving and fueling gensets for my daughter and my 93 year old Mom. I don't think I will ever exceed a 31" tire on the XJ. In the past, I have been able to access any place I wanted by staying on top of the mud/mush typical of SE TX staying pretty close to stock. There are no rocks down here! I don't see this XJ getting much further then NE LA during hunting season although a trip to CO for elk might happen! In the past I have used XJ's to hunt in CO and other then breakdowns they performed well. On one trip, I had to replace U-joint using a hammer and rock and another I had to replace the alternator in the snow. Fun times!

Took the XJ project by the dealership to get the codes read, but they are backed up with service from SW Louisiana because the dealership there was damaged in the hurricane. The service advisor tried the reader that connects to a laptop, but could not read the codes. A stop by a local auto parts store and their code reader only picked up a "engine lean" code (171) and a transmission solenoid clutch code (740)....after, as I drove away the ck engine light came on. I think the tranny needs a good flushing or two and I need to change the fuel filter anyway and make sure I don't have any air leaks at the intake. I am leaning towards just ordering a clockspring as I have the airbag light on, no horn working and no cruise working. I finally have good vacuum after replacing the vacuum reservoir and repairing the vacuum line going to the AC control. I tried another used airbag control module with no success. Need to address issues that prevent it from passing a state inspection. In the old days, we would just pull the offending bulb until the inspection was over! I already replaced the tires with some 235/75-15 Cooper Discovery's as I feared the maypop's it was on.

In my experience with Xj's in the past, its always a chore to keep up with the problems inherit to the vehicle but it is a labor of love/frustration. The earlier years were easier to work on, but lacked the safety features (airbags, anchor points) most of us want. I was looking for a 94 originally but this 99 came to my attention as it is the color (gunmetal pearl) of my first XJ a 1984 I ordered from the dealer.....only offered with a Chevy v6 or a AMC v4 at the time (as I recall). I picked the 4cyl and drove it approx. 100K miles before I found the head cracked in 4 places.....each sparkplug!

Please don't let my rambling from other members expressing their thoughts/experience/ideas on my Project XJ Jeep! It is encouraging to know that I may be doing the work solo, it is not like I am blazing a new trail!

 

Hmm, that should be a AMC 4cyl not v4, but my edit didn't take........

 

Had some time to spend on my XJ project and decided to lock the CAD axle as that was easiest for me at this time.

Put a pan under the axle and took the 4 bolts out of the vacuum actuator/cover, once I pulled the vacuum lines off of it I was left with this...



I thought about researching and using a clamp to fix the collar, but that could cause problems if it didn't hold. I pried the plastic cover off the actuator looking to free the cross bolt that held the collar fork and ended up with this...



From there I ground the center down and it came apart and the actuator was easy to pull from the housing which left a approximately 9/16 hole. I tapped this hole with a 3/8 NPT tap.



Ran to the store and picked up a 3/8 male to 1/4 female fitting and a 1/4 plug. Used those in the hole that used to hold the vacuum actuator



Turned the lifted front right wheel enough to align the two axle shafts up and slid the collar over to the driver's side of the axle



Used one of the C-clips to keep the collar fork from moving in the housing maybe hard to see but it is just to the right of the fork


That rod you see running left to right above will be too long as it is once the actuator is removed. You have to cut about 1 inch off the rod to get everything to fit the way I did it.

Installed the cover with RTV silicone sealant after aligning the fork to the collar and let it sit to cure the silicone a bit and then tightened it down and then snugged up the fittings I installed to seal the housing.



Took the XJ out to a place I could spin the wheels without hurting anything......tried in 2 WD and both back wheels left a trench and started to fishtail. Engaged the 4WD shift to High and you could feel the front end engage, the back end never slipped and it took off straight....but the feeling of victory was short lived... Once I pulled back on the hard surface still in 4WD high it felt like the driveline was binding and dragging big time. Once I put it into 2WD, it drove like it always had. But I also could not get it to go into 4WD low....put tranny in neutral and got to neutral in the transfer case then it hit a brick wall and would not pull into 4WD low. So tomorrow I have to go out of town and work on a creek cabin but when I return I will pull the cover on the front axle and see what ratio it is. I think that is where I will find a problem. If the PO changed axles and never fixed it to actually pull on the front end, I bet he never checked the gear ratio,.

So stay tuned, we may get to the bottom of this..........yet!! If it is the wrong ratio, I will just live in 2WD till the late fall and try and ****** the front axle unit out of the 98 at the U pull it. Then wait till spring to install it. Nothing is going to get in the way of my deer hunting this year!!

 

Latest Update:

Got the chance to pull the cover this afternoon on the front pumpkin housing. I had observed some milky fluid from the vacuum assisted collar lock mechanism and figured it would be a good idea to change it anyway. Found the gear ratio tag as I pulled the cover:



So, if this is the original tag the front end should have 3.55 which would match the rear end.

Now to find out why it feels like it is binding/dragging when 4WD is engaged and can NOT shift into 4WD low.

Any ideas out there?

 

Are your tires all the same size?

 

Yep, probably have about 20 miles on them.....Coopers. Two wheel drive it drives fine.

 

it's possible that whoever sourced out that front axle didn't know xj's and might have sourced one from a 4 cylinder model which comes with 4.10 gears. that would be a large enough gap to bind the gears quickly. 3.73 was quite rare in xj's. my other guess would be 3.07 from a 5 speed xj...

anyone who changes the gear ratio would omit that tag. the only real way to tell would be to open it up and check the gear markings on the ring gear if it's missing the tag on the front axle.

 

I still have the pumpkin opened. The tag pictured came off of it. To double check, I will see what is marked on the gears.

When I got the XJ, you could put it into 4 WD high or 4 WD low with no problem. It would act like it was in those respective gears. But once I moved the collar over to make it "4 WD" and then placed the transfer case in 4WD high is when it acted like it was binding and more like it was in low range then high range.
There was a milky appearance to the gear oil, but I don't think that caused it to act like it was. Once I am convinced the gear ration is 3.55 like the rear, I guess my next step is to move the collar a little and see if that relieves it (In my head, I don't see how....though.

 

your collar is either locked in place or it's not. there is no in between.
once it's locked in place, try putting the jeep in 4wd via the shifter, on loose ground, going in a straight line. if you feel any binding then, then it's definitely different gearing. if you try turning, especially on asphalt, you will damage something, probably your t-case at that point.

you have to determine the gears are the same ratio before you can anything else. the stamping numbers on the ring gear will have a bunch of numbers, but there should be two sets of two, like XXXXX 39 11 XXX this will be the numbers you're looking for. 39 is the number of teeth on the ring gear, while 11 would be the number of teeth on the pinion. divide those numbers and you get 3.5454545455 or something like that. so that is 3.55 rounded up. disregard, if you already know this stuff.

 

caged Thanks for your help, even with the pumpkin tagged as 3.55 it acted like it was a ratio that did not match the rear. I tried it just going straight in loose material in 4WD High and it was like it was in a bind and in low range. The kicker was I could not get the transfer case to the neutral position or close to 4WD low. I had the pumpkin open and searched for the numbers on the ring gear but did not find them exposed. Then late afternoon a (semi emergency) came up and I needed to move the XJ, so I sealed it up, lubed it and when I moved it I tried it again in 4WD High and it acted the same way. (binding with lots of rpms to turn the wheels). I am convinced it is the wrong ratio. I will just have to live with it until I get released to do some "heavier lifting" and swap out the front ends. I don't think I want to think about re gearing this front axle when a U-Pull front end is about $200.

In the meantime, I have a airbag clock spring arriving and will hopefully correct the airbag light being on and horn not blowing so I can get it inspected and licensed.

BTW, the collar is locked as the fork cannot move anymore. What I meant was that when I initially slid the collar over to lock the two axles I moved it so far that the housing with the fork would not fit on the vacuum actuator. I had to slide the collar slightly over the otherway to get the fork to line up with the collar.

I guess when you look at it, it makes sense. While the front end was originally with the collar "open" all the energy was going to the passenger side axle as it was just spinning in the tube. The transfer case did not have a problem spinning a axle with a non matching ratio because it was not grabbing anyway. When I locked the collar it MADE the axle grab with one wheel which probably caused the driveline to bind as the rear wheels were moving at one ratio and the front could not match the rotation and caused more binding.

I am not happy with it but it is what it is, and thats what you get a XJ with a unknown previous owner. Hopefully, I can get it turned around and acting like a stock Jeep XJ which is what I wanted. This one has 175K miles on it, but seems to run smoothly (at least in 2 wheel drive).

 

Unless you've got a 242 t/case, the 231 4wd is only part time and will feel like it's binding on dry pavement at any steering position other than dead straight. The 231 shift pattern is 2wd, 4wd, N, 4lo.

Something else to think about. Are you sure your rear diff is 3.55?

Something else that I'd do is remove that 3/8 pipe reducer and get a 3/8 brass flush plug, install it, drill that out to 5/16, tap it 3/8-16 and put a bolt with a lock nut on it to back up that snap ring. Not tight against the shaft, but just touching it. This will keep the fork engaged if the torque forces the snap ring to pop off.

 

Dave, I have tried twice in loose material to drive straight ahead and it was binding so bad you would think it was in low gear with the front wheels chained to the ground. I have the 231 (part time transfer case) I can get from 2WD to 4WD but that is it, it will not get to neutral or 4WD low. It did before I made it engage the front axles.
I can not be absolutely positive the rear diff has 3.55. But from looking at it, it shows all the signs of being original and the original was a 3.55 with trac-loc. It pulls in loose material with both rear wheels so I would think it does indeed have the original differential. The front was supposed to be a DanaM30/181mm but when I saw the vacuum lines, I knew it was not original to this XJ. I don't think I am going to spend any more time on this front axle/differential. I will just move on to the other things that need attention...the airbag light/horns and changing transmission, coolant and transfer case fluids. The clock spring for the airbag/horn/cruise arrives tomorrow

I appreciate everyone's assistance on this issue. I will update either later this year or early next year on how I resolved this issue.