Vibrations/Grinding From Floorboard

[Cherokeekid88]

I know I have been posting a few threads this week but everything is hitting me all at once. anyways, I took my jeep up to a shop that I usually take it to that builds race cars and they have had it since 8 this morning. Whenever I am driving around usually at higher speeds, there is a constant vibration/grinding that I can feel in the floorboard. The shop couldn't figure out what it was, but I know its there....The front drive shaft is pulled and the only thing I could think that it could be is the axle u joints? but I am sure they checked it...I wouldn't think it would be anything to do with the brakes..they are fairly new (last year)

I am just trying to figure this out without throwing money at it that I don't have

 

[UNCC_99XJ]

My initial thought is rear drive shaft u-joints. Vibes from them can travel a good ways through out the Jeep. You wouldn't really feel vibrations from axleshaft u-joints so much as hear them (clicking, popping..etc).

Do you have an SYE or a tcase drop with your lift set up? Checking the u-joints is very easy. Grab the driveshaft at each end and try to wiggle it (not rotate) around. If you feel play by wiggling it then your u-joints are shot. You could also pull the driveshaft completely off and check it by grabbing the u-joints directly.

 

[Cherokeekid88]

I am running the lowered IRO subframe kit....I didn't even think about checking the rear DS joints....duh! I will check them out tomorrow

What about engine mounts/trans mounts? possbile they could cause the vibration? Would be a nice excuse to upgrade to some Brown dogs

 

[shortxjdoug]

ds joints, pinion bearing, i've had wasted carrier bearings cause grinding noise, outer axle bearings in the rear, unit bearings in the front.... there are a number of things it could be its tough to pinpoint through a written description

 

[Cherokeekid88]

ds joints, pinion bearing, i've had wasted carrier bearings cause grinding noise, outer axle bearings in the rear, unit bearings in the front.... there are a number of things it could be its tough to pinpoint through a written description

My rear carrier bearing in the rear was just replaced about 3 months ago...... I will start with the rear ds tomorrow

 

[Cherokeekid88]

just checked the rear driveshaft and at the axle end, there is no play at all, but up at the tc end, I can hear a little clunking as I move it side to side...can't really feel any slop, but there is some noise going on....

 

[UNCC_99XJ]

Hmmm w/o seeing/hearing it hard to say if it's the u-joints or something in the case..

 

[Cherokeekid88]

Well I just ordered a New tranny mount and I am getting ready to order some brown dog rubber motor mounts...I have been wanting to do this for a while and feel I can go ahead and upgrade while eliminating 2 things at once....with my jeep having 147,000 miles on it and still on the stock engine and tranny mounts....I think they need to be replaced anyways....then after that, if it doesn't solve my problem...then I will look into tearing apart the rear DS, replacing the u joints and checking the t-case....

I don't think the rear u joints are the problem.... I think it is something closer to the front end....It doesn't do it all the time, only at certain speeds and since its not really audible, it would be hard to get a video of it...

 

[UNCC_99XJ]

Brown Dog motor mounts rock. I've got a set of the poly's on my Jeep. Wish I had done rubber's since I was still DDing it at the time, and actually picked up a set of rubbers to swap in, just never got around to it. Very cool people to deal with too!

 

[Cherokeekid88]

OK the feeling is still there! It almost seems it is worst....I am gonna try to describe it in a different way.... When I put my feel on the floorboard while I am driving I can feel like a rotating grind/vibration...when my girlfriend is in the passenger seat, she said that she can also feel it but its more faint on her side.
There is no sound that is produced that I can hear, just feel. At slow speed, it is NOT present...only when I pick up speed do I feel it.
My initial thought now is that the downpipe or part of the exhaust is hitting something, because I have also noticed that when I start my jeep up and its still in park, there is a slight popping noise like my exhaust is hitting something, but haven't had a chance to get under there due to the weather, so I am thinking that the exhaust is resonating while driving causing the vibrations in the floorboard? Not sure....but I am hoping that by installing my new motor mounts(which have taken over 2 weeks to get here) and my new tranny mount...this is gonna raise my drivetrain up a bit from where it is now and help out.....not sure....if that isn't it...then it might be time for a front axle re build

 

[Tacedaddy]

check your exhaust where it passes over the trans crossmember.. thats where mine was making the noise
also could be the shift linkage but im sure you would have figured it out if it was that

 

[Cherokeekid88]

Weird thing is...when I had my exhaust done after the IRO lift, I specifically told the guy, I want plenty of clearance, and I checked everything and it was all good....no rubbing, rattling, clanking, knocking....I even got them to cut out a small piece of my trailer hitch to make a little more room for the tail pipe....

Hopefully my brown dog motor mounts will be here today or tomrrow and I can get those and the tranny mount installed and maybe that will help a bit.....

 

[LawDawg007]

Did you ever figure this out? I have a similar problem that I have isolated to the lf hub bearing or a pinion or carrier bearing. I'll know more this Saturday when I remove the hub bearings.