Help me identify this noise

[hear]

Just did a ton of work on this thing, got it all back together for the maiden test drive, and I've got a new noise. I don't believe it is directly related to any of the work we did, but I have it listed at a high level below. It seems to happen only while accelerating; if I take my foot off the gas it goes away, and it doesn't happen while coasting to a stop. Hard to say if it's happening at higher speeds or not. I didn't catch it on video, but I did hear it through the 1st-2nd shift and the pitch did not change, so I believe it is speed related and not RPM related. In the video you can hear it start and stop as I take my foot on/off the gas.

I put in new axles & u-joints a little over 500 miles ago, used spicer and they installed nice and clean so I don't think that's it. It sounds like it is coming from right below my feet on the drivers side, so I'm thinking exhaust, or maybe front driveshaft?






For background & possible ideas for diagnosis, I just got done doing:

Oil pump
RMS
(exhaust & starter were removed to get the oil pan out)
Transmission pump gasket & relocated vent tube
savvy t-case cable shifter
new trans pan & wiring to a pan mounted sender
new transmission mount

 

[CharlesHS]

Did you replace the driveshaft U joints ?
Do you have a stock driveshaft or do you have a SYE ?
IF you have a SYE; did you replace the CV centering ball assembly ?

 

[hear]

Did you replace the driveshaft U joints ?
Do you have a stock driveshaft or do you have a SYE ?
IF you have a SYE; did you replace the CV centering ball assembly ?

I do have a SYE, I didn’t replace anything on it; installed it a few months ago, no issues. I don’t even know what the centering ball assembly is!

 

[CharlesHS]

I do have a SYE, I didn’t replace anything on it; installed it a few months ago, no issues. I don’t even know what the centering ball assembly is!

Since you have a SYE; check the tightness of the bolt OR nut holding the SYE yoke to the transfercase output shaft.

 

[hear]

View attachment 271211

Since you have a SYE; check the tightness of the bolt OR nut holding the SYE yoke to the transfercase output shaft.

My yoke didn't have that, it just splined onto the output shaft.

Regardless, I will check the yoke nuts...I may just take one drive shaft out and see if it persists. But what made you think SYE, given that I said it felt like it was under my feet? Seems like front shaft is more likely than rear shaft, but then again if I knew I wouldn't be asking.

 

[CharlesHS]

My yoke didn't have that, it just splined onto the output shaft.

Regardless, I will check the yoke nuts...I may just take one drive shaft out and see if it persists. But what made you think SYE, given that I said it felt like it was under my feet? Seems like front shaft is more likely than rear shaft, but then again if I knew I wouldn't be asking.

Noises and vibrations can transmit and appear to be located in other locations....

 

[hear]

@CharlesHS I have no idea what made you focus on the rear driveshaft when all signs pointed to it being more up front, but thanks for your help. My plan was to remove one driveshaft at a time to see if I could isolate it. Obviously removing the rear is easiest, although I wouldn't have even tried it had it not been for your comments here. So I set out on that course, but I didn't have to go far.

Thrilling conclusion: the bolts on the t-case side of the driveshaft were barely in. One wasn't threaded at all, I'm lucky it was even still there. Tightened down, test drove, everything is awesome. Later tonight I'll blue thread lock those bolts (which admittedly I've never done before) to make sure I don't have any future problems.

NGL, I said a big ole prayer before I started this thing up for the first time, and boy was it answered. The skeptics in the room will say it's just bolts & physics...which is true but only works if the operator has some semblance of skill, which I don't. Ergo, divine intervention is the most likely cause/effect.

 

[CharlesHS]

@CharlesHS I have no idea what made you focus on the rear driveshaft when all signs pointed to it being more up front, but thanks for your help. My plan was to remove one driveshaft at a time to see if I could isolate it. Obviously removing the rear is easiest, although I wouldn't have even tried it had it not been for your comments here. So I set out on that course, but I didn't have to go far.

Thrilling conclusion: the bolts on the t-case side of the driveshaft were barely in. One wasn't threaded at all, I'm lucky it was even still there. Tightened down, test drove, everything is awesome. Later tonight I'll blue thread lock those bolts (which admittedly I've never done before) to make sure I don't have any future problems.

NGL, I said a big ole prayer before I started this thing up for the first time, and boy was it answered. The skeptics in the room will say it's just bolts & physics...which is true but only works if the operator has some semblance of skill, which I don't. Ergo, divine intervention is the most likely cause/effect.

Good to hear that you resolved the noise problem....
Experience is why I suggested checking them first.
That would have been an accident ready to happen....