scbrooks87

Ok so I've done a bunch of searching, and I think I MAY no what's causing this, but I'd like to get more opinions. Here's what's happening:


Sometimes, not always, when I'm in reverse and am just idling, there is a slight rumble/vibration that I can feel at my feet and on the gear change lever. It's an AW4 transmission, but I don't really feel like it's the trans because it shifts just fine, and doesn't have any trouble when I accelerate. This morning I also noticed it was doing it in drive and park, which it didn't used to. I can only feel it when at idle.


In my homework, it seems something similar to this happens when motor mounts are going bad? Could it be that the motor mounts going bad are allowing extra engine vibes to come through to the body and through the shift lever when the RPMs are down at idle speed? If so, looks like I'm moving my motor mount upgrade up on its timeline! lol.


Thank you for any input you can provide!


Scott

scbrooks87

Wow, I shouldn't post threads when I'm working. Supposed to say Strange Rumble*** sorry. Can a mod update my thread title to Strange rumble/vibration

Sorry for any other spelling or grammar errors in my first post as well. It's been a rough day haha.

JPXJMOAB

Back yard test.... Have someone sit in your XJ and hold the brake to the floor. Have them burp the gas, look for excess engine movement. But honestly XJ motor mounts are usually so bad you can visually see a crack.

scbrooks87

Thanks for the heads up. I'll take a look at the motor mounts again. I had looked at them when I got it, but not very close.


I'll also do your suggested test to see if the engine moves a bit too much when revving. Can it just be in park when doing that or does it need to be in drive or reverse to see the movement? If I can do it in park I'll just pull the throttle cable myself.


Thanks!

JPXJMOAB

needs to be in gear, reverse would probably be best if someone is looking at the engine.

scbrooks87

Yes, I'd imagine reverse would be the safer of the options!


I'll see if I can get my wife to *not* run me over after work today and we will see what happens. Thanks again.

JPXJMOAB

no problem! You may also want to try cleaning the throttle body and IAC. That gave me a rough idle a while back, cleaned them up and it runs like new!

scbrooks87

Just watched a YouTube video on how to do those things. Seems like that is a really simple project that won't take long at all. Regardless of everything else, I'll be doing that soon lol.

cruiser54

Look here:

scbrooks87

Anything in specific I should look for to be wrong in that area? Am I checking there to see if the transmission mount looks to be going bad?
Thanks for the help!

cruiser54

Make sure the exhaust pipe isn't real close to the cross member.

scbrooks87

Understood. I'll check it out. If it's too close, I'm guessing I can just tweak the exhaust hanger to get it a bit further away?


If it makes any different, I really can't hear the vibration or rumble from outside the XJ, it's only when I'm inside that I can tell it's going on.

scbrooks87

Actually, I've done more looking, and I think I see more clearly what you mean. If the exhaust is close to the cross member, that showing that the trans mount is basically shot, cause it's squished down so much. I'm learning!

cruiser54

More than likely your trans mount will be sagged and/or your motor mounts crapped out.

scbrooks87

Well, I did the test in reverse and revved it up, and the motor definitely has some movement beyond what I think would be normal, so definitely looking to get motor mounts. The transmission mount also looks to be squished down and crapped out, so that's on the list too.

Ok, should be the last couple questions here. I've decided on the Brown Dog motor mounts, they seem indestructible. What about the transmission mount? I'm having a hard time finding the right one for the 4.0l engine with an AW4 and that fits a 1999. Is there an aftermarket upgrade worth getting? If not, anyone have a link to the right mount so I know I don't end up with the wrong one?

Thanks!
Scott