Horrible rumbling/grinding coming from under car?

[namfbroh]

Okay, so I'm really hoping somebody can shed some light on wtf is wrong with my car. Whenever I drive in rain, I can be driving for a little while, then I notice a small rumble that gradually gets worse and worse until I need to pull over. When it happens on the highway, I need to stop completely before it will go away. It seems like I need to keep the clutch out until the trans slows down or stops before I can drive again normally, but I'm not positive about that. When I'm on the road going 30mph or so, all I need to do is slow down a bunch and it'll go away. It rumbles in every gear. Wheels are on tight and weighted properly.

I also have a welded diff, so is driving through the puddles messing with the diff and carrying the disproportion to the trans and causing the rumbling? I'm just shooting ideas out, but I don't really know. I did some research and a few people(of various car makes/models) were saying water in/on the exhaust.... however it doesn't seem to rumble in neutral or when I rev in neutral or at idle and stopped.

Anybody have any wisdom they can share?? Sorry for my wall of text, but I wanted to be thorough in my description.

[namfbroh]

OH, just realised, I swapped the entire driveline out of my old 240 into another shell and I recall it happening in both cars. However, I also recall it happening when I had an open diff. I'm also getting a lot of results from various car forums saying it's their exhaust hitting the body/driveshaft/sway bars/etc.

Has this happened to anybody else?

[je_decoy]

after i turboed my ka i hadnt noticed that my down pipe was like a 1/4inch away from my steering coloum. then after i had gotten up to around 65 on the highway it started to make contact from driving vibrations. really freaked me out at first but nothing major. hope this helps.

[NAVY-ET]

it sounds like a bad driveshaft

[namfbroh]

it sounds like a bad driveshaft

Do you mean driveshaft or carrier bearing?

[murda-c]

Yeah sounds like a carrier bearing.

good excuse to get a solid aluminum one

[camaro379ss]

^^+1 carrier bearing

[namfbroh]

alright thanks guys, hopefully this solves my problem.

[namfbroh]

Sorry to revive this, but my problem is persistent. I bought a nice one piece driveshaft from FRSport, put it in, and that seemed to reduce a lot of vibration and yields noticeably better acceleration. In any case, I was driving back from an event today and got caught in a downpour, and sure enough the rumbling is back, even worse.

I've now ruled out the driveshaft, I've got brand new nismo motor/trans mounts, multiple sets of wheels all balanced properly, the problem was present with both an open diff and a different(welded) diff. I'm convinced that it's drivetrain related. All I'm really left with is the transmission, but what's wrong with it? Syncros? How would water affect a bad trans?

Any suggestions are really appreciated. This quite frankly scares the shit out of me, especially in busy traffic and nowhere to pull over.

[D. Joy]

I seem to be having similar symptoms. Usually happens for me while the car is drifting. Just looking for some answers.

Rain seems to make the vibration happen more often. Sometimes I can feel something actually hitting under my seat a little more towards the transmission tunnel. Exhaust?

Seems to show itself during high rpms if I let off the accelerator too.

Anyone have any more advice or info?

[tommytwo40hands]

if you feel something slapping under your seat it has to be the exhaust..the same thing happened to me everytime it would rain..freaked the shit out of me..the only explanation I could find was the rain was making me want to get sideways..and with the increased vibration from the motor, it would rattle my header bolts loose...

when your car is cooled down grab your exhaust(before the cat) and shake it, if it moves tighten the bolts..other than that I'm not really sure what it could be

[tommytwo40hands]

Op I'm not sure if this ^^^ will help you..sound like your problem is in the drivetrain ..maybe change your diff fluid...just throwing out ideas

[fliprayzin240sx]

I got a guy I helped do his 5 speed swap with the same issue. His situation, the car would rumble when on low speed and coming to a stop. Its not the engine or the transmission since the shifter isnt even vibrating, feels more like its coming from the back of the car. Anybody else got an idea what it could be. I was thinking the driveshaft too but it doesnt explain why it only does it when its coming to a stop. Figured if the shaft is out of balance or the carrier bearing is bad, itll be doing it more the faster it goes.

Its fine when I come to a stop and leave the car in gear. But the moment I pop it out of gear, it starts to rumble and vibrate the car.