'98 TJ Questions

No, the image posted above is in fact correct for a conventional driveshaft. The pinion should only point at the transfer case when a single double cardan shaft is used. The reason the above image is correct is because the u-joints do not have a 1:1 turn ratio throughout a complete rotation. Setting them up at opposing angles cancels out the difference in rotation.

For a DC shaft, the DC joint itself is designed to cancel itself out, so the pinion u-joint should have minimal angle, aka the pinion should point at the transfer case.

Both of the below images are correct and applicable to a TJ:
View attachment 87396View attachment 87397
Thanks for the info. I was not aware.
 
  • Like
Reactions: TJ Hunnicutt
JeepCJTJ - It 'shudders' while letting out the clutch pedal. I can reduce the shudder by riding the clutch and using 1500-2000rpm. I have ramp up into my work carpark and in first gear accelerating up it will also 'shudder'. Its not long enough to get up to any sort of speed so it could just be that I don't have enough RPM

Im going to take it into a 4wd mechanic and get them to do a complete once over the entire thing and give me a list of stuff that needs fixing. Hopefully they can do abit more investigating and let me know what it is....

I dont get any form of vibration of shudder or anything at any other time other than taking off from a stop.. I am actually really impress by how smooth the 4.0L actually is!
 
Sounds like a flywheel. May also be a bad pilot bearing, broken/loose transmission mounts, or broken (they are almost never loose) motor mounts.
 
I’ve checked mounts and they all look ok...
I’ve got it checked in next week for a check over so i’ll See what they say.
 
Watch control arms when one shudders, can be involved.
 
Took the TJ on roughly a 600km (370-400miles) trip on the weekend. All on road with a small amount of off roading.... It did the job well.. It was loud, slow and consumed all the petrol but went well!
I think I need a new throw out bearing, noise when clutch out, disappears when clutch engaged.... Anyway off to the mechanics in a few days for a health check and we'll see what they say
 
I’ve been doing some reading on jeep gearbox noises and I’m wondering if this noise is ‘normal’ for these gearboxes?? I’m guessing I have the ax-15.. are these boxes known to be noisey? Otherwise it could be input shaft bearing not the throw out bearing
 
I’ve been doing some reading on jeep gearbox noises and I’m wondering if this noise is ‘normal’ for these gearboxes?? I’m guessing I have the ax-15.. are these boxes known to be noisey? Otherwise it could be input shaft bearing not the throw out bearing
Actually the AX-15 is a relatively quiet transmission that is used an all sorts of vehicles. Rarely will you get a front bearing noise out of it unless you have completely ran it out of fluid at any point.

That said, your throw out bearing is not touching anything if your foot is not on the clutch. It is sitting on the input shaft with no pressure. If you rest your foot on the clutch then you move it to the cover and it starts touching something so don't do that. Take your foot off of the pedal if you are not using the clutch. If your clutch makes noise when you push the pedal down then it is most likely your throw-out bearing.

If it is making noise when you take your foot off then it can be your front bearing but it can be something else also. Although the AX-15 usually has a good reputation, unless you run out of fluid or run the wrong fluid in it.

That is not to say your AX-15 is just not wore out. But my AX-15 has just shy of 200k and grinds downshifting into second and upshifting into 5th, but it is quiet other than the grinding. Sometimes a little rough getting into reverse, again though you wouldn't know it to listen to it idle.

From what you are describing it does sound like your front bearing is going. It is rare, but it happens.

Just to reiterate.
If you are in neutral and your foot is not on your clutch pedal then the engine is hooked to the transmission, so you have spinning shenanigans going on in the trans. Once you push the clutch in then you are using the T/O bearing to disengage the engine from the trans. That means that the trans actually quits spinning, but now your T/O bearing is spinning.

So to break this down
If you have it in neutral, and clutch is not depressed then your pilot bearing is being used, Your front bearing is being used your input shaft bearing is being used and your counter shaft is spinning but no torque to the output shaft.

My guess, not hearing your noise, is that it is most likely a bad front trans bearing as you suspect, but it could be caused by bad fluid or even a bad pilot bearing. In any case, it sounds like your trans is going to have to come out.

I hope some of this ^^ makes sense.

Maybe first check your fluid, and try replacing it with some GL4 fluid and see if it quiets down?
 
  • Like
Reactions: TJ Hunnicutt
Yeh that all makes sense.. i’ll Give the GL4 a go and see if that makes any difference.. what weight do they take?
The it is a whirring kind of noise that only happens with foot off clutch and goes away when you depress the clutch

I need to do the flywheel anyway so gearbox will be coming out in the near future. Is the input shaft bearing easy to replace?

Hopefully I can keep daily driving it for the next month or so before I can get a chance to pull the gearbox...
 
Yeh that all makes sense.. i’ll Give the GL4 a go and see if that makes any difference.. what weight do they take?

I need to do the flywheel anyway so gearbox will be coming out in the near future. Is the input shaft bearing easy to replace?

Hopefully I can keep daily driving it for the next month or so before I can get a chance to pull the gearbox...

This is the fluid I run in mine:
https://www.amazon.com/gp/product/B002INJ69I/?tag=wranglerorg-20

You can probably get by cheaper with some other GL4 oil, but I am quite fond of this. I think Mopar make some but it probably isn't much cheaper. I have heard of others using Royal Purple, but again this is the only thing I use.

I don't know how technical you are, but I would look on craigslist and see if you can find a used one cheap and swap it out, then maybe take on a rebuild then sell that one back maybe?

I think technically you can get the front bearing out without a teardown, but it will be really hard and really just as hard to get the new one back in. My suggestion is if you don't want to do what I suggested above then take the trans down and replace all of the brass at the same time. It will all be just as hard at that point.

There are a lot of good videos on how to do it. I would scrimp on cheap snap ring pliers though. Good snap ring pliers will be essential. If you are mechanically inclined at all which it sounds like you are. If you take your time, you can rebuild the trans.

if you don't care about money I found this also: (Brand New AX-15)
I actually find this quite reasonable for a brand new AX-15
https://www.advanceadapters.com/products/26-ax15--aisin-ax15-5-speed-transmission-new/
 
Mmmm well.. I don’t really have the money to do any of it right now haha but it is what it is. If it’s just a matter of splitting the case pulling the old bearing out and putting a new one in I can do that.. I am pretty mechanically capable it’s just time to things done that I’m lacking these days...

Can you drive around on a bad input shaft bearing??
 
Last edited:
Mmmm well.. I don’t really have the money to do any of it right now haha but it is what it is.

Can you drive around on a bad input shaft bearing??
You can till it totally breaks, if it does, chances are your trans will be garbage at the end.

Well if money is an issue then you have to do what you have to do right?

You can try and fight the old bearing out and fight a new one in if you have too.

Or you can keep driving it around. I would probably change the fluid as it may give you some more life.
(don't get that confused with repairing. It won't fix anything just might prolong further wear for a while.)

You can do nothing, and keep driving it while you watch craigslist for a used one. People are always changing their drive train and sell those. In my old Jeep I put Chevy running gear in and sold the factory Jeep stuff. People do that.

You could make sure the front bearing is the actual issue too.

I mean if you are changing the flywheel then pull the trans, and check your pilot bearing if it is excessively warn it could make your input shaft not sit pefectly straight and it would make some noise. There are a few things that it could be.

One thing to note that usually a bad pilot bearing will make noise when you just let off the clutch. It will squeal really fast then be quiet mostly. If you didn't hear that, I would be shocked if you see any issues with your pilot bearing, but again I didn't hear the noise so I can't really diagnose your issue.

If the front bearing is super bad you should be able to tell once you get the trans out and pull the front cover off of the trans.
 
Shouldn't you be running

Red Line 50305 MT-90 75W90 GL-4 Gear Oil - 1 Gallon https://www.amazon.com/dp/B002INX20C/?tag=wranglerorg-20

That's what I run. You are not allowed to be different. :)
Either is fine, I just went a little thinner because I have a little grindy grindy in mine, that I am trying to prolong till I have stupid money to fix it.

Really I think the only difference is mine is 75 - 80 and yours is 75 -90. The previous owner was running straight up gear oil, so I wanted something a lot thinner. It actually worked, I rarely grind down in 2nd now, and about 50% grind going up in to 5th.

At some point I am going to rebuild it, but I need to whack away at some more other projects first or it will just have to completely crap out on me.
 
Yeh I wouldn’t be planning on driving it for long just a month or so until I can get around to dropping the gearbox..

I’ll give the oil a change just to be safe and plan on changing clutch etc. and I see if any gearboxes come up for sale.
 
  • Like
Reactions: ac_
Yeh I wouldn’t be planning on driving it for long just a month or so until I can get around to dropping the gearbox..

I’ll give the oil a change just to be safe and plan on changing clutch etc. and I see if any gearboxes come up for sale.
I just noticed that you are in Australia, It might be much harder to find a used trans there. I don't know. I wish you luck. Feel free to hit me up with any questions you come up with.
 
Yeh there are some around but they are expensive.
I might even pull the trans check the bearing and if it needs replacing take it too a trans place and get them to replace it
I also thought that my shudder and input bearing could all be related and being caused by a bad pilot bearing..
 
Last edited:
Yeh there are some around but they are expensive.
I might even pull the trans check the bearing and if it needs replacing take it too a trans place and get them to replace it
I also thought that my shudder and input bearing could all be related and being caused by a bad pilot bearing..
It is possible that the clutch disk is not doing its job. The springs on the disk are to stop the shutter.

Im not saying that it is your problem. But if you are going to pull the transmission take a hard look at the disk.

 
Yeh right... Well I think I might replace the clutch, pressure plate, TOB, pilot bearing and put some new proper oil in the gearbox, check the input shaft bearing play and see if that helps! Hopefully that'll fix all my problems!! Doubtful but im always optimistic about these things ha