what the heck is hitting my floor?

[philip_g]

you can hear and feel something when you hit a bump bouncing off the floor, seems like a stupid question but I've wiggled everything I can lay my hands on underneath and can't find anything loose enough to make a racket.

Don't suppose this is some stupid little common thing that just doesn't come up in a search? :doh:

[blue95xj]

when does it do it, and where does it sound like it's coming from?

[ADVNTURR]

Could be something like a worn out tranny mount allowing the transmission to move. Another possiblity might be a worn lower control arm bushing since that would place the bump right under foot. Just 2 ideas.

[Dr. Dyno]

you can hear and feel something when you hit a bump bouncing off the floor, seems like a stupid question but I've wiggled everything I can lay my hands on underneath and can't find anything loose enough to make a racket.

Don't suppose this is some stupid little common thing that just doesn't come up in a search? :doh:

Check the exhaust. If there's a loose support, it could move around more than normal.

[jeepinandy]

Motor mounts??

[Matthew Currie]

Check the clearance between the exhaust pipe and the crossmember. It's minimal at best, and when the transmission mount begins to sag (it need not be broken or loose) it will often knock on bumps and when the engine idles. Wear in the exhaust mounts themselves will make it worse.

[langer1]

Pets and Children all accounted for?

[philip_g]

I think the trans mounts are a good possibility, it was cold today and it's worse in the cold, for awhile I could make it rattle if I lugged the engine a little while engaging the clutch.

it feels like it's right underfoot, I'll get under there and mine around some more, thanks for the tips!

[MAP]

Check your sway bar bushings. I have 127,000+ miles on my 99 XJ and have had to replace the things at least twice. When they get worn you fell a knocking/rattling sound when you go over any bumps or dips.

If you get underneath and pull down on the swaybar and see a space between the bar and bushing above the bar, then they are probably worn. These are changed pretty easily.

Another similar knocking came when my exhaust was hitting the transmission crossmember. I don't have the original exhaust though.

MAP

[philip_g]

the sway bushings are definitely shot, but I don't think it's my problem, I think those are causing a little rocking motion when you go over bumps
on the list to change :)

[laredo]

Gremlins
:')

[JeepDawg]

I had the exact same thing after having my transmission replaced. I would feel something right under my feet. I thought, "OK, maybe I'm being too picky." Then, on the way to church, the transmission almost falls completely off. Check the transmission mounts....quick.

[ckh550]

Check the clearance between the exhaust pipe and the crossmember. It's minimal at best, and when the transmission mount begins to sag (it need not be broken or loose) it will often knock on bumps and when the engine idles. Wear in the exhaust mounts themselves will make it worse.

I currently have the same issue, exhaust got knocked a little loose on my last wheeling trip, and now it hits the crossmember. Sometimes it just rattles it, and sometimes it's a knock. But it's a good thing to really look at closely.

Chris

[Hypoid]

Get some help. Have someone hold the brake, feather the clutch enough to load the driveline in forward and reverse gears. Some other brave soul has to look underneath while power is applied.
BTW, I'll be working on the mom-mobile if you want to drive to Golden. I'll check in around 3:00 to see if there are any IMs.

[philip_g]

Get some help. Have someone hold the brake, feather the clutch enough to load the driveline in forward and reverse gears. Some other brave soul has to look underneath while power is applied.
BTW, I'll be working on the mom-mobile if you want to drive to Golden. I'll check in around 3:00 to see if there are any IMs.

thanks for the offer but I'm in the office today, after my all day crank pulley cluster yesterday I'm not feeling working on it today anyway :D

[philip_g]

I had the exact same thing after having my transmission replaced. I would feel something right under my feet. I thought, "OK, maybe I'm being too picky." Then, on the way to church, the transmission almost falls completely off. Check the transmission mounts....quick.

I worry about that or shucking a driveline or something, you never know..

[Hypoid]

It's almost my weather, just a little cooler. LOL

I've been following the posts on the local forum, wanting to go play. The little XJ needs more attention before I trust it that far. LCA bushings today, uppers are on order. Ball joints next week, maybe I'll have a skid made for the new tank by then...

[Smittty9785]

check lower control arms on front axel. bushings?

[philip_g]

want to do mine too? LOL

all my bushings are shot, front end is loose but I'm confident she's not going to leave me stranded.
I want to try redcone but should probably get some more experience first.

[G.Q. Jeeper]

I had this very same problem with my old TJ, not sure if its the same or not...

Its right under your feet eh? My problem turned out to be the busings that attach to the transmission from your 4WD leaver, it was the bracket thingy, I posted this up on the TJ board, and they told me to go to an aftermarket one like Skyjacker, cause the factory ones are bad.

You can feel my rod, just go under the Jeep and grab it and wiggle it, the rod will have play in it....

Hope that helps...

Jeff

[MAP]

philip_g,
Replace those bushings and see if you notice a difference. If they are bad, I'm certain that they are causing some rattling/knocking.
They only take a couple minutes to replace.

MAP

[philip_g]

philip_g,
Replace those bushings and see if you notice a difference. If they are bad, I'm certain that they are causing some rattling/knocking.
They only take a couple minutes to replace.

MAP
having never done them, how do you get them off? Just lube up the bar and slide or are they split on the top? :confused:

[MAP]

The bushings are split. Do one side at a time. With the Jeep sitting level, remove the 2 screws on the bracket holding the bushing in place. The bar should sag enough to remove the old bushing which is split. The new bushing should be split as well. Put some lithium grease on the inner surface of the bushing, open it up at the split and slide it over the bar. The new bushing is not as easy to put on as the old one is to get off. Tighten the 2 screws on the bracket and you're done. Now do the other one.

Good luck.

MAP

[Hypoid]

want to do mine too? LOL
That's gonna cost ya some Papa Murphey's. LOL Offer is still open, just have to find a time. I'm trying to get the front tightened up for new tires. No sense throwing good money after bad; no extra money either. Going through the grief now will pay off in tire life and fuel economy.

I took maybe 90 minutes to do both lower arms. Probably did it the hard way; one at a time, without lifting. Getting the crusty bolts out took some time, passenger side is always worst. Once you get the arms off the Jeep it's not so bad. Make note of how everything orients. The hole on the flange side of the bushing is slightly larger, the arms have a slight angle built in. I used PB-Blaster, a vise, and small hammer to drive the bushings. I clamped the old bushings in the vise (the flange has two flats on mine) and turned the arm around the bushing to break it loose. Getting the arms back in place took some persuasion, the new bushings don't line up the same.

I'm still waiting for the upper bushings. I'll probably take them when I do Ball Joints. Mine take a star bit to remove the axle end. Last spring when I changed out the front axle they were a real bear. My fetish with anti-sieze will pay off again! LOL

[philip_g]

have yet to find a bolt on this puppy that was a match for the impact gun.
even the rear shock bolts came right out (now I've jinxed it)

[Hypoid]

I fianally got the little XJ off the ramps: Changing just the lower bushings made a noticeable difference. I'm psyched about getting this done now!

While underneath I noticed that the uppers and lowers connect to the body about six inches apart. If you drive with your left foot on the part of the floor that slopes up to the cowl, it is literally on top of these mounts.

[Gordy]

My XJ had a similar noise, turned out to be lower shock mounting bushes.

[xylonjay]

I had the same problem. It was the exhaust pipe hitting my crossmember. It drove me nuts until I wedged a rubber exhaust mount donut (cheap fix) in- between the pipe and crossmember. It isnt fastened to anything, but it has stayed put for about a month. And the knocking is completely gone.

[joecool]

Since this thread has been brought back, I am experiencing something similar. Is there an easy way to tell if my transmission mount is worn out?

[Semper Fi]

do you have a T-case drop on your Jeep? I had one on mine and the bolts that hold it in place has stripped out and were allowing the T-case drop to move around.

[tkjeeper]

I have an interest in this post as well, have the same intermittent knock, rattle when I hit the right sequence of bumps. I have repaired the exhaust mount that attaches to the crossmember but still there. Tranny drop is solid, 6" of snow today so I think I'll check it later. I think I'll go in this order, sway bar mounts, LCA mounts, shifter linkage, tranny mounts....etc. Keep us informed if you completely solve it, problem I've heard with unibody's is the sound can sound like it's under you when it's coming from another area. Keep us posted.

[Wallyman]

usually its honda civics ...that i hear under my jeep >: )

[joecool]

do you have a T-case drop on your Jeep? I had one on mine and the bolts that hold it in place has stripped out and were allowing the T-case drop to move around.
I have Rusty's crossmember with the one inch drop. I dont need it anymore, since I have an SYE, but I dont want to spend money on a new one. I checked the crossmember bolts, and they all seemed tight.