02DroptopZ

iTrader: (3)

2 weeks ago, I had my car on the dyno. After my first pull, my trans tailshaft housing cracked wide open. My tuner said he “felt something wrong” at about 6000rpm and he ended the pull. To fix the problem, I bought a truck tailshaft housing, BMR relocation bracket, and an adjustable full length torque arm. I got it all installed yesterday, and went for a drive..

Starting at about 35mph, getting its worst at 40-55mph, the noise starts. It’s a very violent banging sound. When you hear the bang, the whole car shakes and it feels like it slows down. If I put it in neutral the noise almost seems like it goes away. Also, when I’m on the gas, the noise seems to lessen. You can also hear it bang once when the car shifts gears.

I got underneath the car and let it run on jackstands. I can’t pinpoint the noise, but I can feel the tailshaft housing bang a little, the torque arm a little more, and the rear end is shaking pretty good.. the noise sounds like it’s coming from the driveshaft though, not the rear itself.

I tried flipping the driveshaft, checking it for damage, checking to see if the TA or exhaust is hitting the car, retightening the bolts, and readjusting the pinion angle.. All with no change. I’m out of ideas. Anyone have any suggestions? My car is a 2002, automatic, with 33k miles if that helps any. Thanks!!

02DroptopZ

iTrader: (3)

Just to add a little more info to this.. I got under the car and messed with the driveshaft. The rear end side is firm and tight, but the front that goes into the trans wiggles around (maybe ¼ or ½ inch?) and makes a clunking noise.. I also noticed a small amount of fluid had come out around the seal of the tailshaft.. Keep in mind this is a brand new seal. I believe this is where my problem is. What could cause this?

jastone

What type of motor mounts do you have? What type of trans mount do you have? Did you check the trans mount, is it busted?

I put poly motor mounts in last year when I did my header install. I left the rubber trans mount in at the time, I had a little vibration at about 50-60mph, after 60 the vibe basically went away. Nothing bad I figured maybe since the car was lowered perhaps it was pinion angle issue that the poly motor mounts revealed or it was the rear pinion or wheel bearings possibly going bad (10 bolt whined a bit).

Fast forward this year, I bought a Moser M9 which comes with a new crossmember for the trans and it's own torque arm (a fine piece BTW), which has solid rod ends. I knew the solid rods ends would transmit more road feedback. After the install I took the car out and I thought the thing was gonna vibrate into pieces at about 45 mph! I instantly went back and adjusted pinion angle which ended up taking care of about 70% of the vibes. After a couple of more pinion adjustments none of which helped the vibe I decidd to eliminate easy things first. Found that the rubber trans mount was about ripped in half and without the rubber bushing from the factory torque arm to no longer reduce the transmission movement it was able to move around a lot more and cause excessive noise. I changed the rubber mount out for an energy suspension poly mount I had left over from the header install and VIOLA! No more vibes, car is smooth as silk now at any RPM and any MPH!

I know people say don't use poly trans mount but if you have poly motor mounts it seems to work, at least for me it did. Rubber motor mounts= rubber trans mount. Poly motor mounts= poly or rubber trans mounts.

Hope it works out for you man. It's an easy simple fix for sure!

SPDKNGG

Sounds like a drive shaft is out of balance... Could be a bad Universal joint.
Take the car to a reputable driveline technician before you cause more damage and possibly kill yourself and or other motorist.
When driveline problems start, it can get real ugly, real fast!

02DroptopZ

iTrader: (3)

I have a stock trans mount and stock motor mounts. When I had the trans mount off it looked fine though. Your post is very interesting, because when I first took my car out, the same thing happened. Really bad vibes, I readjusted the pinion angle, then it got much better except for this specific speed.. I think I’ll pick up a new trans mount, I know they’re pretty cheap. Thanks for the suggestion.

I drove the car a mile down the road, turned around and went back, honestly it sounded so bad I thought the driveshaft was going to fall out before I even made it back.. Thank you for the suggestions. What could cause the driveshaft to become unbalanced or u-joints to just go bad so randomly though? Would a bad u-joint make it possible for me to wiggle the driveshaft even though it’s fully installed? I appreciate the help!

SPDKNGG

I drove the car a mile down the road, turned around and went back, honestly it sounded so bad I thought the driveshaft was going to fall out before I even made it back.. Thank you for the suggestions. What could cause the driveshaft to become unbalanced or u-joints to just go bad so randomly though? Would a bad u-joint make it possible for me to wiggle the driveshaft even though it’s fully installed? I appreciate the help![/QUOTE]

I have seen a driveshaft torqed so bad it crump pulled the center just enough to cause the same problem you are describing...car has a transbrake and 4500 stall.
Another example, the torque converter stated to go. Some of the welds gave up on one side. causing the converter to become unbalanced.That was due to the pump failing.
And another one was the flex plate was cracked around the bolt holes..

Let us know what you find.

02DroptopZ

iTrader: (3)

Well, I took the car to a shop and had them look it over. They checked pinion angle, bolt tightness, driveshaft balance and straightness, u-joints, etc.. They ran it up in the air, took it for a drive, and couldn’t figure out what was causing the noise. They figured out some of the vibration was coming from where the exhaust was banging on the rear crossmember, but the banging is still there.. As soon as you let off the gas above 35mph, it sounds like the driveshaft is going to fall out.

Anyone have any more ideas?

SPDKNGG

Weird!
Ok, well the next thing i would do is load the car on a dyno and look at the car while the said noise occurs and see what's exactly is going on.
Hope you find the issue.

02DroptopZ

iTrader: (3)

Ok, time to update this thread for those curious, or incase anyone comes across this in the future. I know it pisses me off when I find a thread with someone having an issue identical to mine, and they never post a conclusion.

So, I got under the car, and the noise was really starting to make me think it was coming from the rear end. If you touched the rear with your hand, you could feel the vibration the most there, and it clunked pretty bad. I found one locally, identical to the one I had (3.73), so I swapped it out. No change. Noise and vibration was still there. So then, I called a driveshaft specialty shop. I dropped off the shaft, and like I expected, nothing was wrong. Perfectly in balance, U-joints ok, etc… Ok. Next idea.

At this point, I realized I had no other option. I called Finish Line, ordered a Level IV 4L60E, and dropped my car off at BackStreet Performance. I went on a ride with a tech, and he brought his scanner.. He seems to think the noise is actually something in the tune. The car is showing it is in 4th gear at 22mph, and the converter is trying to lock then too.. The converter is locking right at 35mph, which is immediately when the knocking starts. I noticed if you ride the brakes (unlocking the converter), the vibration goes away completely. He seems to think that the large cam + locking at 35 is causing a ton of bogging and slack, which could very well be possible. It's running 1100 RPM @ 35mph, and you can hear the thing loping. Not sure why my previous tuner did this if this turns out to be the problem...

I will update this once they get the trans in and installed and finish the tune that the other shop left incomplete.