I have no idea why it became loose in the first place. It was a slow process, the noise progressed over a long time from barely detectable to easily and constantly audible. One things that irks me is that almost two years ago my driveshaft center support bearing went bad and I had a shop replace it. Either the tech didn't bother to torque down the nut after he re-installed the driveshaft, or it managed to loosen again in a very short time after I picked up the car from the shop, because the noise was there both long before and after that repair. I had also asked another tech at a different shop if he thought this nut could be loose, and he said no it wouldn't be the source of the problem.

The nut can't be turned by hand and it's not a visible part under the car so it seems to be something that is easy for a tech to overlook. Typical sources of noise are always the exhaust or suspension. Even most two-piece driveshafts have a slip-yoke, not this odd, split-ended, female splined connection with male intermediate shaft.

I'm just hoping it stays torqued down and that there hasn't been any damage to the splines since they've been loosely connected for the last four years.

 

ancdmd, glad you finally solved your mystery-noise problem. I found some torque specs for the adjusting nut, but not sure how you would do the torqueing without the SST shown.

 

I certainly didn't have the SST. The nut was definitely at less than 51 ft lb. I wasn't able to use any kind of a torque wrench on it so I just tightened it best I could knowing that it should be around 50 ft lb. I didn't put a pipe extension on the wrench handle or anything so I don't think it could get much tighter than 60 lb ft at best, given that I could barely turn the nut before I had to reposition the wrench due to the obstruction of the exhaust. Funny in the diagram that they use two SST's; I just put the car in park and let the engine/trans keep the driveshaft from moving

 

I just had Lexus attempt this fix. Unfortunately, it didn't work for me. The noise is either coming from a different place, or they tightened the wrong bolt.

 

How would you describe the noise you're having?

 

It sounded just like your YouTube video. I will try to upload a video. It sounds like a tin can rolling down the street. It is really prevalent if I shift into neutral and coast, but I hear it anytime I accelerate/decelerate as well as when I get in the "sweet spot" for RPMs (around 2k).

Your fix makes total sense to me, that's why I'm wondering if Lexus was in the wrong area. Are you positive the noise is gone?

 

 

Hmm while similar, your noise sounds vaguely different. Does it sound like it's coming from the transmission tunnel area, or somewhere else? How often does it occur and under what conditions? Has it been steadily getting louder/more frequent/worse?

 

I'm not sure exactly where it is coming from. To me, it sounded like it was coming from the front of the car. It happens every time I get in the car. It started out very faint and only when I would hit the accelerator and let off. So the twisting of the drivetrain causes the noise. As time has gone on, it has gotten louder, and now also occurs over bumps. There's a cobblestone road near my house that makes the noise very prevalent. I've also noticed if I shift into neutral and coast, the noise becomes extremely prevalent, higher frequency and more violent (the car is an automatic transmission, but I shifted it into neutral while coasting to see if the noise got louder). Any ideas on what would be more free to wiggle around in neutral?

 

Yes I'm positive the noise is gone, it's a night-and-day difference. If you're able to at least get the rear wheels up on jack stands you can check the driveshaft yourself, just reach up where it comes out of the back of the transmission, grab it and try to rotate it back and forth quickly. It should be solid and not make any noise.

Sorry I missed your previous post. Sounds to me like your noise has to do with something near the engine and not the driveline. When you hit the accelerator the engine moves a bit, which could cause a loose part to become either looser or more in or out of contact with another part. Have you had your exhaust thoroughly checked? There's an area where the exhaust can sag and come into contact with a crossmember, it's near the middle of the car before the resonator assembly. It may not be contacting when the car is sitting but with it running or over bumps it can bounce around quite a bit. What kind of maintenance history has the car had and how many miles does it have? Have the motor mounts been changed?

 

I am so excited your found the problem!! Will have to get under mine and see if it is the same. I am pretty sure it is....

 

Thanks for the response! My exhaust was checked, but not thoroughly. It has 150,000 miles on it now, and I have been doing most of the maintenance myself since 100k (struts, brakes, rotors, wheel hubs, spark plugs, etc. ). Motor mounts have not been changed.

 

I'd say a good starting point would be to replace your motor mounts and the trans mount. With your car's age and mileage I think it's safe to say those parts are toast.

 

Okay, thanks! I changed the transmission mount not too long before this noise started. I wonder if that could be the culprit? I will have the engine mounts looked at.

 

i just wanted to come on here and thank the original owner of this thread. i was having similar noises coming from what i though was right under me and sounded exactly like the youtube video so i hopped under my car today and popped off the heat shield and support beam and got a large adjusting wrench around the driveshaft adjusting nut and made micro adjustments tightening it until i was satisfied and took my car for a ride and the noise is completely gone. i’m so glad i didn’t take this to a mechanic because this is definitely something a mechanic might easily overlook. either way, it worked and unsure if the noise will come back but if anyone is wondering, it 100% got rid of my noise.