Please help identify this noise

[GatorDoc]

Hey guys,
I posted a video of my 1975 EB automatic. It is making a loud grinding/whining type noise with acceleration. It is first noted about 16 seconds into the video. After that I am accelerating then coasting a few times so you can hear the noise come and go. It appears to come from the transfer case but I am not sure. The TC was recently off to get a new intermediate seal. It was making this noise before the work. The universal joints were changed as well. Any ideas?
https://www.youtube.com/watch?v=Rmwl-cln5zg

 

[Crush]

Sounds like its in low range

 

[DirtDonk]

Well that's an unhappy sound doc!
First I would remove the rear driveshaft and drive on the front to make sure it's not isolated to the rear. That sound could be a bad component in the trans, transfer case or driveshaft I'm thinking.
Heck, it could even be engine related. Just not sounding as likely. My first thought is actually driveshaft, but might as well start eliminating things quick so you don't drive too much and make it worse.

I know you said you replaced the joints, but did you mess with the centering yoke and ball of the CV section? Ever lubed the joint through the small (and often hidden) female grease fitting?

Put oil back in the t-case when you got it back together?;D
What type?

When did it start? Just out of the blue, or did you make any mods like a lift kit or such?
What all has been done to the rig overall?

Paul

 

[GatorDoc]

Hey guys,
It does have a 2.5 inch suspension lift on it. The constant velocity joint was replaced on the rear drive shaft along with the universal joints. The front drive shaft universal joints were replaced. All of the universal joints and the drive lines were lubed. I made carefull attention to reinstalling them in the same orientation they were removed as. Basically marked everything them lined the marks back up with reinstall The transfer case was removed( it was full of transmission fluid). The intermediate seal was replaced and everthing was put back together using new seals. Again carefull attention was made to make sure the roller bearings remained in place. I used a Permatex gasket maker to adhere the TC to the tranny and refilled the TC with a synthetic 75-90 gear oil. It is not leaking and appears to function correctly. In the video I was running it in front neutral and rear high. The noise started right after I got it back from restoration. I had it mechanically sound first then it sat at the body repair/paint/etc shop for over a year. I noticed it some when I got it back but after finding the transmission fluid in the transfer case, felt that was the cause. Obviously not.
Also to add one more variable to the equation, i am the guy that started the thread with the crack running through the area where the vacuum modulator inserts. I am readying to get another C4 but in the interim cold welded the vacuum modulator in. It is holding fine with no leak and great shifts(good vacuum).
This sounds and feels like TC. I look forward to the advice and thank yall for your time.
G

 

[GatorDoc]

UPDATE.
Well guys I did as DirtDonk suggested and dropped the rear drive shaft. The noise diminished extensively. Its probably only 25% of what it was but its still there. Now that its quieter I can make it out a bit better. It sounds like a metal scraping noise. Like a bad wheel bearing. But it seems to be isolated to the transfer case. Any ideas?

 

[DirtDonk]

Can you grab the output yoke and feel if it's loose at all? OR maybe even while doing that, put it in neutral and see if you can feel any roughness when spinning it by hand.

This might indicate either an issue with the output section bearings, or perhaps (not sure about this) the interface between the input and output that might be effected by those roller bearings.

Just throwing that out there. Maybe more D20-versed minds can come up with some more tests.

Paul

 

[GatorDoc]

No noise at the yoke. In neutral it spun freely and quietly. I guess its time to take the TC back down and have a professional take a look.

 

[GatorDoc]

Hey guys,
I got the transfer case out and torn down. For those of you that care......the noise was the front output shaft bearing. It was worn down to the point where you could feel the ridges. Hopefully will have it all back together soon.
G

 

[half cab]

Hey guys,
I got the transfer case out and torn down. For those of you that care......the noise was the front output shaft bearing. It was worn down to the point where you could feel the ridges. Hopefully will have it all back together soon.
G

Yea we care. It's always good to find out alotto times peeps never report back.