AX15 bad synchro? bad clutch or T.O.? Perplexed!

Hi Folks... I am really hoping someone can give a helpful opinion here - I've been looking all over and the 'net for similar problems though I can't be sure the few other similar symptoms match mine.

Since getting my XJ back from a (barely) failed smog test, I now seem to be having some sort of gear lashing/slippage problems. Mostly it's happening in 2nd or 3rd gear when under load. Going up hills it happens a lot. Going down, almost never. There's definitely a sort of mechanical sound being made by SOMETHING - but I can't be sure if it's the transmission (I feel NOTHING through the shifter that i can recall). Though the AX-15 DOES have about 275K miles on it... I haven't changed the transmission fluid yet (seemed like a good first check) - but that will be pending finding some of this RedLine™ stuff that everyone seems to recommend... so i cannot yet confirm if there is gear loss. The 'grinding' sound doesn't really sound like gears to me though... it's 'smoother' somehow.... and SEEMS to be coming more from the passenger side and more forward of where i normally hear gear clash noise (when shifting into reverse for example)...

I thought it MIGHT be the clutch - since it's mostly when it's under load... but i can engage each gear firmly and engine power seems to translate into wheel RPM responsively... also there's this NOISE it seems to make - which I am not sure the clutch would do... the clutch is a centerforce II and has been GREAT since i installed it originally in 2000. (50K miles driven since then)

I considered whether it might be the throwout bearing ... though they don't really seem like throwout bearing symptoms (shifting is super easy - when i had T.O. problems before - i had a difficult time shifting and engaging gears). So - I'm really not sure about this...

anyone care to take this on?

add'l details: 92 XJ sport 4.0HO (1998 engine) with AX-15 etc

Early warning sign of a dying TO bearing?

Do you engage first gear, and then reverse or go directly into reverse? If not that is why why you hear teeth gnashing going into reverse.

Have you tried coasting and breaking in neutral and lifted the jeep to test for brake and axle and u-joint noises?

Noises on these beasts can wonder and be very hard to figure out what and where they are coming from. Been at it for 12 years now. I still find new ones.

Drain the old oil and look for signs of brass fines, or other metal.

Use MT-90 Redline only!!!!

hi thanks for the valid points.. it's not actually the reverse gear clash I am concerned with - I was only mentioning that as something to compare to... in saying 'it sounds nothing really like that at all'...

i have checked the u-joints yes. It doesn't really seem like it would be the u-joints or brakes though due to the loss of power when this 'transmission or clutch slip' seems to happen (i shouldn't think?)

I will be able to check out any gear trash once i get my hands on the redline - and yes i was planning to use that - as i mentioned above. thanks for now...

A dragging brake would cause power loss. I just finished dealing with myself.

I mentioned it because I was not aware for 40 years how to properly engage reverse without grinding the gears, which is how I trashed my first and only trashed manual. It broke a tooth off the reverse gear and later made other sounds and problems requiring a rebuild. Been too long, forget what the noises were. If you know what reverse gear grinding sounds like I was thinking perhaps you too were not taught to engage forward first, then shift to reverse to avoid any grinding going into reverse?

"hi thanks for the valid points.. it's not actually the reverse gear clash I am concerned with - I was only mentioning that as something to compare to... in saying 'it sounds nothing really like that at all'..."

Sooo....there's a noise and you lose power going up a hill? Am I reading this right?

I would be checking to make sure your transfer case is engaging all the way.

Ecomike said:

I mentioned it because I was not aware for 40 years how to properly engage reverse without grinding the gears, which is how I trashed my first and only trashed manual. It broke a tooth off the reverse gear and later made other sounds and problems requiring a rebuild. Been too long, forget what the noises were. If you know what reverse gear grinding sounds like I was thinking perhaps you too were not taught to engage forward first, then shift to reverse to avoid any grinding going into reverse?

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GOOD THING you reminded me though... I just haven't been driving it for a few years (it was sitting for a long time) - I used to be in the practice of putting it in first, first... but probably forgotten... I thought, if anything- that you could only damage the reverse gear doing that (?) I guess not...

old_man said:

I would be checking to make sure your transfer case is engaging all the way.

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Yes - though it happens on flat too.. but just more often when under load... going up hill...

but i GUESS - now that I THINK about it... once my gear is engaged - it COULDN'T REALLY be the fault of the transmission if I get 'slippage' (i.e. I don't think there's a way for the transmission to 'disengage' - I never come out of whatever gear i'm actually IN) - so it MUST be clutch or my throwout bearing????

or am i wrong about the above?

old_man said:

I would be checking to make sure your transfer case is engaging all the way.

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how can i do that, old man...?

OKAY! well seventy three dollars of RedLine later - i've done my lube change and drove it around the block a few times... STILL GRINDING but it does (?) seem to be doing it less perhaps (?) I guess I 'll have to get out a bit more and see what gives. Although the grinding has been heavily on the increase and only really started 20 miles ago... I guess it's pretty likely to get worse. I suppose it (the redline) was a gamble i had to try... just in case... albeit a pretty expensive one.

Why Redline MT-90 only? I put their MTL in mine. I had chased issues with my AX15 for a while, got it rebuilt, pilot bearing went bad, caused all kinds of havoc with my system. Now I just cant go from 4th or fifth to third, I have to bump second to shift to third.

sinat01 said:

Why Redline MT-90 only? I put their MTL in mine. I had chased issues with my AX15 for a while, got it rebuilt, pilot bearing went bad, caused all kinds of havoc with my system. Now I just cant go from 4th or fifth to third, I have to bump second to shift to third.

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Well NOW ya tell me... i would have gone for the MTL based on what i'd read on their site but everyone seemed so rabid about using the MT90.. i figured they must know something i don't...


Gosh - really? I"ve NEVER been able to downshift at ALL (in any way) on my AX-15 - someone once explained to me there was some sort of 'lock out' to prevent downshifting on the AX-15... which bummed me out a lot (cause i LOVE downshifting) but I got used to it pretty fast.

Well looks like the MT90 was a big waste of money anyway- the grinding is worse than ever it seems (I can sort of avoid it by shifting at 2500 vs 1800 or so RPM). So - I guess I'll be looking for some kind of rebuild... as long as I can rule out the xfer case...

NeXJ said:

GOOD THING you reminded me though... I just haven't been driving it for a few years (it was sitting for a long time) - I used to be in the practice of putting it in first, first... but probably forgotten... I thought, if anything- that you could only damage the reverse gear doing that (?) I guess not...

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A broken tooth off the reverse gear can damage anything else in the box

NeXJ said:

OKAY! well seventy three dollars of RedLine later - i've done my lube change and drove it around the block a few times... STILL GRINDING but it does (?) seem to be doing it less perhaps (?) I guess I 'll have to get out a bit more and see what gives. Although the grinding has been heavily on the increase and only really started 20 miles ago... I guess it's pretty likely to get worse. I suppose it (the redline) was a gamble i had to try... just in case... albeit a pretty expensive one.

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Could the clutch itself be worn out and slipping and making the noise, rivets scrapping the pressure plate?

Or a slipping clutch pack in the transfer case (wild guess, as I have little experience with them)

sinat01 said:

Why Redline MT-90 only? I put their MTL in mine. I had chased issues with my AX15 for a while, got it rebuilt, pilot bearing went bad, caused all kinds of havoc with my system. Now I just cant go from 4th or fifth to third, I have to bump second to shift to third.

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I do not know anyone using MTL, many are using MT-90. No other reason, MTL may be OK too.

Ecomike said:

Could the clutch itself be worn out and slipping and making the noise, rivets scrapping the pressure plate?

Or a slipping clutch pack in the transfer case (wild guess, as I have little experience with them)

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The only transfer case that has a "clutch" is the quadra-trak (249 I think). It has what's called a " viscous coupler". Fancy word for part time clutch. Allows the 60/40 power split. It's also expensive and I just swap out a 242 or 241.


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And since I have no experience with the ax-15 ( although I want to swap one into my 2k xj) I don't think it would be syncros because it's under load. If 2nd and 3rd gear are on the counter shaft maybe bad counter shaft bearings? Does it make the same noise in 5 th? (If 5th is on the counter shaft. ) and looking at schematics maybe shift fork misalignment ? Not letting it get into a gear all the way?


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NeXJ said:

OKAY! well seventy three dollars of RedLine later - i've done my lube change and drove it around the block a few times... STILL GRINDING but it does (?) seem to be doing it less perhaps (?) I guess I 'll have to get out a bit more and see what gives. Although the grinding has been heavily on the increase and only really started 20 miles ago... I guess it's pretty likely to get worse. I suppose it (the redline) was a gamble i had to try... just in case... albeit a pretty expensive one.

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How was the fluid?

In your situation, i wouldve dropped the fluid to a new oil pan, and re-used it. Worst case scenario youd find shavings, which would mean you will be rebuilding soon, why waste the fluid? As you mentioned, its expensive.

If it was your syncros, you wouldve found this: