[-=DeanstuD=-]

OK, I used the search function for over an hour...

1987 YJ 4.2 BA10/5 132k miles. Never off road until 127K miles.


I get a thump thump thump from the transmission when in gear. It goes from an audible clank to a tactile thump to perfectly normal feel without sound depending on how you hold the shifter.

On or off throttle doesn't effect it, but it only happens IN gear and changes with drive train rotational speed, not road speed. It happens the same whether in 4 hi lo or 2wd. i.e. in low range it is faster than in high range but not 'different'.


Placed in either first or second gear hands off, there is a slight audible thunk. Hand on shifter it is no longer audible but you can feel it. If you push t'word the right, it becomes louder even to a clang noise/bang feel. If you pull to the left it completely goes away and you can't even feel a problem.

3rd gear seems perfectly normal, except for the moment you are pulling it out of gear, then you can feel a bit of a thump.

4th gear is just like 1st and seccond, but it is opposite IIRC (damn I should go test it but it's late).

5th gear has an audible clunk and thump, but IIRC it goes away if pushed to the right.



I know I know, it is a POS french trans, throw it out. OK OK. I would rather not do that right now. First for money reasons and second because of weather.

It is not a daily driver, I have other cars/trucks/jeeps for that. It is only used for wheelin' Is it safe to just drive it this way, holding the shift so it is quiet all the time? I don't mind a breakdown and tow, (I DON'T WANT TO) but if it would last ok I could go play and fix it in the spring/summer. What I am afraid of is would it suddenly lock up the wheels and send me cartwheeling down the highway on the way to the woods?

[rustywrangler]

Sounds like you got yourself some worn out internal parts. When was the last time you did a fluid change???

If you want it to last till spring, it sounds like your ok at the moment. I would avoid Highspeeds personally. It is NOT going to just LOCK UP on you. IT will grenade before it does that. BUT, if your to that point, either way its gonna be interesting when it goes.

YES, I am one of those that says get rid of the POS but I also understand the reality that you may not be able to do that at this time.

SO I would just make shure everything is tight IE, the shifter is not loose on the mount and you do a fluid change.

[Richmond88yj]

Sounds from the description like a u-joint going south, not the trans.

Have you noticed a change in your above description slowing down in gear or downshifting?

[-=DeanstuD=-]

Richmond88: U-joint was my first guess, because I heard the same kind of noise on my brothers XJ before... But I have looked and they are fine. Also on or off throttle doesn't effect it, but it only happens IN gear and changes with drive train rotational speed, not road speed.


RustyWrangler: The fluid was changed maybe less than 200 miles ago? I really don't know because the speedo/odo hasn't worked since it was changed.

I payed a guy off of Craig's list to change my clutch slave. He had me give him new fluids and sent me off to buy some new seals too. He didn't say anything about the fluid looking bad or havening shavings. Fluid didn't look bad to me when I saw it later. I did notice the next day on a test drive, that the speedo/odo didn't work. I called him and he offered to come back and fix it, but I didn't want him to drive back here so far. He said it probably just needed seated and told me how to do it.

I didn't do it because I am admittedly lazy when it is wet out. and I only use it for the woods after all. Anyway. So I towed it about 120 miles, went wheeling for the day, no water holes, just wet gravel and some packed snow and puddles, no "bogging" er whatever. It was an old stage coach trail. Total wheelin was about 50 miles going by my brothers trip meter, but then he has 35's and stock trans gear thingy.

Ok. so towed another 120 miles back home.


It just sat in the driveway for a couple months until I had a new years day trip come up. I charged up the battery and gave a once over under the hood, and a little maybe 5 mile test drive. All seemed fine. Next morning I drove about 50 freeway type miles to our meeting spot. While people were getting ready, I do remember noticing that the trans felt a little 'stiff' in the neutral slop check, but chocked it up to the fact I just hadn't driven it in a while so I just wasn't used to it.later it seemed 'normal' again.

Total wheeling that day was only about 10 or 15 miles, but was tough going as it was REAAAALLLY deep snow. everything seemed, and felt and drove perfectly normal on the 50 mile drive home. The next morning I noted my left rear was getting low, and i figured it was probably about finished. It was pretty bald anyway. So, a couple of days later I loaded up 2 used tires i had plans to mount in the future when those went bad.


OK now here it comes


I headed twords the tire shop in town, and once again no problems. the trip was only maybe 5 miles, and as I pulled into the tire shop parking lot I felt the clunk bang as I have described it.

I was too early for the tire shop to open so I headed to McD's for some breakfast and test drive feels of WTF is broken.

I looked underneath thinking I was loosing a joint but all seems fine. I went and got the tires mounted and headed home 5 miles maybe. That is all I have done except maybe 1 mile test feeling since.


I know it is a book, but I am trying to give as much detailas possible since you can't see hear or feel it. TIA

[Richmond88yj]

How tight are your trans/skid bolts? Also is the outrigger on the trans skid snug?

//trying to eliminate everything before trans work.

[-=DeanstuD=-]

I don't know what an outrigger is, but I did crawl under and check out every bolt I could find. All are tight. I checked the fluid, and there are no metal chunks, and the oil looks just like caramel. Not as thick though.


I removed the shift boots, and the shifter and bolts are tight.

So, since I don't know what else to check, I mean I suppose there is nothing to check. I will look for a used AX15?

What vehicle do I wanna grab one out of? I don't know if the FAQ is going to apply to me, because I have an 87, it should have an 207, but I HAVE CONFIRMED that it is indeed a 231J.


So I have a Frog trans and a 231............

[Richmond88yj]

If it's not the U-joints and not the mounting hardware... Guess it's the trans, but it sure seems impropable than the trans would "clunk" and still shift fine and drive ok.

Any manual 94+ Cherokee or Yj will have an AX-15. Swap is straightforward. Search "AX-15 swap" for the write up on how to do it.

[rustywrangler]

[QUOTE=Richmond 88 YJ]If it's not the U-joints and not the mounting hardware... Guess it's the trans, but it sure seems impropable than the trans would "clunk" and still shift fine and drive ok. Mine clunks like there is no tomorrow and still shifts. I can actually feel it in the shifter.

Any manual mid 89+ Cherokee or Yj will have an AX-15. Swap is straightforward. Search "AX-15 swap" for the write up on how to do it