Marble sound in transmission, kills engine in neutral. Where should I start looking?[1989 Jeep Comanche 4.0L]

[james-mc]

Hello new comanche owner here. I got a 1989 Jeep Comanche Pioneer with the 4.0 I6 engine and a 5spd 2WD manual trans (I think it might be an AX-5?). My girlfriends dad gave it to me for next to nothing. Ran and drove fine (20mi to my house at least). 

Today I was going through the truck to see what needed fixed/replaced. Topped off fluids and tested some bad/not functioning components (radio, HVAC blower motor, Oil Pressure Switch, change burnt out dash bulbs, etc.)

While the truck was idling I noticed a horrible sound. Like something was loose inside the engine. I'm thinking it threw a rod or something. As I went to turn the engine off the sound got louder and the engine died. Imagine putting a handful of marbles in your dryer mixed with a baseball card in a bike spoke. That is the kind of sound it was making.

I restarted the engine and with the clutch fully pressed I did not notice the sound. However when I release the clutch the grinding clunking sound would reappear and kill the engine after a few seconds. 

The trans was in neutral but when it would die it would act as if the tranny would try to engage. 

That at least narrowed the issue down to the transmission..i hope. I was able to drive in 1st and Reverse (just about 15ft in the yard, didn't wanna mess anything up worse).  Nothing out of the ordinary. The issue only seems to happen when the truck is in neutral. Engine starts then after a few seconds the sound appears then not much longer the truck will die. And when the engine dies its like the clutch tries to engage. Kind of similar to killing it at a stoplight by releasing the clutch too fast.

 

So now it is parked until I can pinpoint the issue and fix it. I called my dad over and he told me it could possible be the throw out bearing. Before I buy any parts I wanted to get your opinions.

 

I've done some tranny work on my old saturn but never had anything like this happen. What should I look into replacing first?

 

[Big Dan]

Someone else will chime in with more info. Based off what you said (noises), throwout bearing seems likely.

Tranny will either be BA10/5 or AX-15 (depending on when the truck was made as 89 was a switch over year). AX-5 was a 2.5L transmission.

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[Dzimm]

Yeah the clutch and throw out bearing are suspect, may even be a flywheel bolt come loose or something.  

 

I'd go ahead and pull the trans and see what you find with the clutch.  If you heard pieces flying around you'll probably find them in the bell housing.

[derf]

Something let go and is jamming up when it's running.  Either clutch bits or transmission internals.  You'll need to drop the transmission to find out.

 

The fact that it doesn't rattle when the clutch is pushed in makes me think it may be the transmission.

[james-mc]

Thanks for the replies. I'm hoping it is the throw out bearing. I've read that input bearing could be issue. I hope its not the IB as from what i seen that's pretty much a whole teardown of the tranny. When it dies its not an instant lockup. Its almost like the clutch is catching( or at least trying to) and killing the engine the same as letting off the clutch too fast from a stop. The sound seems to come from where the trans meets the engine. Man id rather have an engine issue, its more familiar territory lol. The only trans work I've done was replaced clutches nothing more. 

[87MJTIM]

To test the internals, I would drain the transmission fluid and look for metal parts 😱. Then you may know which direction to go. 
 

[james-mc]

38 minutes ago, 87MJTIM said:

To test the internals, I would drain the transmission fluid and look for metal parts 😱. Then you may know which direction to go. 
 

Will do. I'm going to work on it tomorrow evening. Tonight I'm going to head to the JY for some of the other parts I need. I suspect the issue lies somewhere in the bell housing that's where the sound seems to be coming from. I don't think the transmission is locked up or anything. It just seems to catch a gear or something if truck is sitting in neutral. Even after the engine dies and I restart the engine it will run normally for about 30 seconds. But I will check for metal in the tranny fluid 1st, then onto checking the clutch. Also I am going to try and see if i can find the part number on the trans so I know which model it is.

[scaleless]

Throwout bearing or loose flywheel bolt sounds easy, but if something is dragging the engine down only while in neutral, I can't imagine it would be in the bellhousing.  Unless the sound is still there while in gear at idle speeds, I guess.  Either way, finding a badge on your transmission isn't necessary for identification - they're easy to visually identify.  The BA10 is split horizontally along the transmission and bolts together along the top ridge and the rear.  The AX15, on the other hand, is split along a vertical medial plate just forward of the shifter hole, with the front and rear housing bolted together through that plate.

 

 

(This is a 4WD version, so ignore the rear)

AX15 (again 4WD):

Failing that, just post a photo and we can identify it for you.  It's not entirely necessary unless you determine that your transmission has given up the ghost, though.  That said, if you can narrow it down to the transmission and not the engine, you'll probably have to pull it anyways.  You might want to crack the case open and visually inspect it at the very least.

[Jesse J]

33 minutes ago, scaleless said:

Throwout bearing or loose flywheel bolt sounds easy, but if something is dragging the engine down only while in neutral, I can't imagine it would be in the bellhousing.  Unless the sound is still there while in gear at idle speeds, I guess.  Either way, finding a badge on your transmission isn't necessary for identification - they're easy to visually identify.  The BA10 is split horizontally along the transmission and bolts together along the top ridge and the rear.  The AX15, on the other hand, is split along a vertical medial plate just forward of the shifter hole, with the front and rear housing bolted together through that plate.

 

 

(This is a 4WD version, so ignore the rear)

AX15:

 

Failing that, just post a photo and we can identify it for you.  It's not entirely necessary unless you determine that your transmission has given up the ghost, though.  That said, if you can narrow it down to the transmission and not the engine, you'll probably have to pull it anyways.  You might want to crack the case open and visually inspect it at the very least.

the way I easily tell these apart is the ba10 is split the long way and the ax15 is split the short way

[james-mc]

Ok I was thinking and I have a theory. So the shifter doesnt have a bezel. Just the boot kinda flapping there. And i did notice I was one panel screw short but it was getting dark. My screw cup was on the center hump near the shifter, its possible i dropped one while putting screws in the cup. So i figured it was on the floorboard and Id get it when its daylight. Now I'm thinking...could be that damn screw made its way into my gearbox? I know if that's the case I will probably win the award for dumbest comanche owner on earth lol. I won't know for sure until tomorrow when i search the cab for that screw. I do have a flexible magnetic grabber and I have access to an endoscope that my buddy has. But it has me thinking that the noise and symptoms could also be that panel screw in the transmission, right?

[james-mc]

2 hours ago, scaleless said:

Throwout bearing or loose flywheel bolt sounds easy, but if something is dragging the engine down only while in neutral, I can't imagine it would be in the bellhousing.  Unless the sound is still there while in gear at idle speeds, I guess.  Either way, finding a badge on your transmission isn't necessary for identification - they're easy to visually identify.  The BA10 is split horizontally along the transmission and bolts together along the top ridge and the rear.  The AX15, on the other hand, is split along a vertical medial plate just forward of the shifter hole, with the front and rear housing bolted together through that plate.

 

 

(This is a 4WD version, so ignore the rear)

AX15:

 

Failing that, just post a photo and we can identify it for you.  It's not entirely necessary unless you determine that your transmission has given up the ghost, though.  That said, if you can narrow it down to the transmission and not the engine, you'll probably have to pull it anyways.  You might want to crack the case open and visually inspect it at the very least.

When i was under the truck the tranny does have a similar shape to the ax15. Ill check for sure tomorrow.

[scaleless]

7 hours ago, james-mc said:

But it has me thinking that the noise and symptoms could also be that panel screw in the transmission, right?

 

Unlikely if the transmission is making noise in Neutral and it's an AX15. It's split by the medial plate and the shifter is on the output shaft side, which is not spinning in neutral - if a screw fell down it would have great difficulty traveling across the plate.  Also it probably would have caused some catastrophic damage in short order.  That said, if it took a few teeth off another gear, those probably wouldn't have trouble sloshing around! You should get a new boot regardless - Crown P#  83500520.

 

Here's a photo of my AX15, for reference.  You can see how its split down the middle by a big plate, input on the left, output on the right.

[james-mc]

10 hours ago, scaleless said:

 

Unlikely if the transmission is making noise in Neutral and it's an AX15. It's split by the medial plate and the shifter is on the output shaft side, which is not spinning in neutral - if a screw fell down it would have great difficulty traveling across the plate.  Also it probably would have caused some catastrophic damage in short order.  That said, if it took a few teeth off another gear, those probably wouldn't have trouble sloshing around! You should get a new boot regardless - Crown P#  83500520.

 

Here's a photo of my AX15, for reference.  You can see how its split down the middle by a big plate, input on the left, output on the right.

That's good to hear. I am going to crawl under the truck tonight. And thank you for the pic I might need it later. I'm going to try and take a video of the problem maybe that will help show exactly what i mean.

[ghetdjc320]

Sounds a bit like a loose flywheel bolt to me. You’ll likely see some metal flake in the tranny oil by the way. Never opened a manual tranny that didn’t have a bit of flake in it from the synchros. Most people just can’t drive stick plus those synchros are wear items. So no need to suspect a major problem from metal dust unless you see actual fragments in the oil or a truly excessive amount of metal dust. 

[james-mc]

Alright so I was able to get a picture of the ID plate of the transmission . It looks like a Peugeot BA10/5. I tried to take a video to replicate the issue but it seems there are even more issues.

 

First being whether you're in first gear or reverse the engine will die. Although if your riding the clutch in first gear it will roll for a little bit but once you fully let off the clutch it dies. In Reverse the truck just doesn't move and then dies when I let off the clutch. 

 

If the clutch is pressed the engine will run. But regardless of gear or neutral it will die once you let off the clutch.

 

Also I noticed that now you can put it into any gear without the clutch pushed in. I was unable to do this before. It looks like there is some fluid leaking near the driveshaft.

[james-mc]

1 minute ago, ghetdjc320 said:

Sounds a bit like a loose flywheel bolt to me. You’ll likely see some metal flake in the tranny oil by the way. Never opened a manual tranny that didn’t have a bit of flake in it from the synchros. Most people just can’t drive stick plus those synchros are wear items. So no need to suspect a major problem from metal dust unless you see actual fragments in the oil or a truly excessive amount of metal dust. 

Unfortunately I was unable to get the drain bolt off. I will most likely have to grind down a cheap 1/4 inch extension. I hope its something simple though lol. I have a week off at the beginning of April. That's when I hope to fix this trans. I know something is wrong I just don't know what.

[87MJTIM]

yep, that's a BA 10.

 

Word of advise: Open the fill plug BEFORE you open the drain plug.  (Think about it.)

 

[james-mc]

I will have to find the fill plug for this trans. I'm think I'm going to need to drop the transmission and inspect the bell housing first. Then work my way into the gearbox if nothing looks torn up. The way it sounded like something was loose in the transmission and now it seems to just lock up makes me suspect some bearing or gear is broken and chunks of metal is locking it up. I have a haynes manual coming, hopefully it will help me out with this transmission.

[87MJTIM]

Just my opinion, but start searching junkyards close by to find an XJ with a manual trans.  You would want 90+ for model years.  (89 is split: 1/2 BA, 1/2 AX)

[OldManComanche]

Drain the oil, see what comes out. Try a magnet in the drain hole and see what sticks to it.  You are going to have to remove the transmission no matter what is wrong.  

My guesses are:

 Bearings worn out or balls missing,  chewed up gears etc. trash in the trans act.

Syncros sticking or broken

 Trying to go into 2 gears at once or gear sliders not moving to neutral (worn shift mechanism)

 You might see if you can remove the shift lever and look down inside to see if the shifting rails are all in neutral, may not be shifting completely out or in to gear.

 

   Good Luck

 

[james-mc]

1 hour ago, 87MJTIM said:

Just my opinion, but start searching junkyards close by to find an XJ with a manual trans.  You would want 90+ for model years.  (89 is split: 1/2 BA, 1/2 AX)

I've seen 1992 and 1993 Cherokees around but they have 4WD transmissions. Mine is RWD unfortunately.

[87MJTIM]

Didn't see that.  Yeah, that's an issue.

 

It's just that a BA 10 is not worth fixing (if that is the problem).

[james-mc]

33 minutes ago, OldManComanche said:

Drain the oil, see what comes out. Try a magnet in the drain hole and see what sticks to it.  You are going to have to remove the transmission no matter what is wrong.  

My guesses are:

 Bearings worn out or balls missing,  chewed up gears etc. trash in the trans act.

Syncros sticking or broken

 Trying to go into 2 gears at once or gear sliders not moving to neutral (worn shift mechanism)

 You might see if you can remove the shift lever and look down inside to see if the shifting rails are all in neutral, may not be shifting completely out or in to gear.

 

   Good Luck

 

I will try that. Ive been searching for another 2WD trans I can swap in. But no luck so far. 

[james-mc]

5 minutes ago, 87MJTIM said:

Didn't see that.  Yeah, that's an issue.

 

It's just that a BA 10 is not worth fixing (if that is the problem).

Right. If I could come across an ax15 at the JY Id pick it up but any and all jeeps Ive seen are 4wd. 1993 and up. I might not have much of a choice besides try to fix or pay high dollar for a trans. I'm trying to look up any other vehicles that would have an ax15 that I could swap in but not much luck there either.

[87MJTIM]

Was the AX15 installed on Toyotas? I thought I read that somewhere.  However, if it did come on a Toylet, the bellhousing would not fit a 4.0.  The BA10 BH won't fit to an AX15, either.

 

So, that leads back to an XJ or YJ.

 

Two years ago, there were two XJs in a local LKQ with AX15s.  One was a 4wd with an internal slave cyl. bellhousing; the other was a 2wd with an external slave cyl. BH.  I left there with a 4wd and a BH for external slave cyl.  Long day.