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Clunk!!! Update: Found Metal Bits in rear diff!!!

Stomis said:
Bet you whatever was clunking is still bad but your not noticing it because you dont have a super high idle from a vacuum leak.

My vote is still a trans or engine mount.
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Well, you were kind of right, I replaced the trans mount and it got better, but is still there... However it is only noticable in drive (doesn't do it in overdrive) and it also goes away or is less noticable when the transfer case is engaged... Now the noise sounds like it's the rear end, but then why wouldn't it still clunk when in 4 wheel drive? Both my transfer case and my rear are leaking slowly, so both are in need of attention, but $$$ is tight and I'd like to finally resolve this one. No obvious play in the rear and ujoints are new.
 
new guy shady

it may still be the rear end, lots of stuff to get loose in there. when you put it in gear or let off the throttle the torque is switching direction in the rear. when transfercase is engaged the mass of the gears and chain, front end all that, will act as a sort of shock for the transfer off power. also could still be the flex plate crack somone else mentioned. i had that happen in a camaro i had.
 
yes motor mounts! I had the same thing happen. Then one day it was making a god awful grinding sound. Had a buddy come meet me at in a parking lot where this transpired and he watched the motor shoot half way out of the engine compartment when i hit the gas! The motor was seperating itself from the transmission!
 
Hmmmm... I know it was suggested before, not sure why I never investigated it further. My trans mount was in pretty sad shape, so it would make sense. What should I look for? Is some play acceptable??? What's the best way to check them? Whenever I've swapped engines, I always put new mounts in because they are cheap and there's no better time than when the engines out... It's funny that in 20 years of tinkering with cars, I've never had to deal with any issues like this. I feel like such a newb on this one... I've rebuilt motors, tinkered with fuel injection, i guess it's the fear of the unknown...
 
Haha, I guess I wouldn't use "metallic" to describe it... Used to do it when I would shift from Park to drive or drive to reverse, but I also had a high idle issue that was causing it to slam into gear. Now it will only do it if I'm in a rush and try to take off before it's idled down after startup, or if I take it out of overdrive and shift into drive. Then if I let off the throttle from hard acceleration or mash it while coasting it clunks or thuds and you can feel it. I just wish I could narrow down all the variables, I hate throwing parts at anything... At this point I'm thinking I'll check the motor mounts(might just change them for the fun of it), change the fluid in the transfer case(cause who knows if it was ever done), and pull the rear diff cover, see what I find, and change the fluid while I'm in there since the covers leaking anyhow... Transmission had a fluid and filter change about 10,000 miles ago, and was given a clean bill of health by the trans shop. He was the guy that steered me towards finding my vacuum leak/leaking intake manifold issue, I originally thought I had a transmission problem.
 
Hey smier, I got a similar problem too. Its only slightly different in that it only happens when putting the truck in D or R, and back again. It's that switching direction thing. I replaced the mounts, all 3. I've gotten under the truck while someone shifted back and forth. It sounds like its in the TC. "Metalic thunk/clink. Once on the road I hear nothing.

I read though this whole thread and like the ideas. The chain one scares me, hope it's not it. But is the chain even used in 2wd? My diffs where just inspected and fluid changed. It's been like this forever. So maybe it's the tailshaft, which would equally suck.

Let us know how that trans mount works out.
 
I actually already changed the trans mount and it made things better, but didn't fix the problem... I guess that's the fun of fixing up old vehicles, figuring out the five different things that are causing what would seem to be one problem...
 
It sounds like a loose chain in the tc.mine was like that and ended rubbin a hole through the bottom of the case.
 
Chulisohombre, where are you in Bangor? I used to live in Stone Church, near Portland... Now I'm down in Easton.
 
Pull out the tcase and rebuild it. It's not terribly difficult. I put an SYE on a 241 in an old TJ, and it was seriously a 45 minute job.
 
Heres your candidates after re-reading this. Just check this stuff out and throw a wrench on the bolts for the sake of knowing its good

Loose bellhousing bolts

Cracked flexplate

Loose adapter bolts from tcase to tranny

Loose u bolts

Loose crossmember

Now the more serious issues:

Tcase chain is shot

Issues with rear axle

If its not the stock exhaust perhaps the drivetrain movement is clunking on an exhaust pipe, I've seen that...
 
smier said:
Chulisohombre, where are you in Bangor? I used to live in Stone Church, near Portland... Now I'm down in Easton.
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I live on south main across from the park.my truck is ready 2 wheel this summer.just tryin 2 get it good enough 2 pass ins now.
 
K85 Octane said:
But is the chain even used in 2wd?
.
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yeah, i could have swore the chain isn't moving in the case while in 2wd, only engauges when put into 4wd.

I'm still gonna say either bad motor mounts letting the engine jump alittle and thump on the mount pad, or something int he rear diff is about ready to retire.
 
Ok, I had some nice weather today so I got to tinker a bit today. First had a coworker help me check the motor mounts, they are good. Next I changed the fluid in the transfer case, it's been slowly leaking so no surprise it was a bit low. No debris or metal in the fluid, and it looked and smelled ok. I could see the chain thru the drain and the fill, and could move it with my finger... Is the chain supposed to be that loose or is a certain amount of play acceptable?
Next I checked to make sure everything is tight and no broken bolts, ubolts, etc.... Everything else looked ok.
Lastly, I decided to open up the rear differential and have a look... Surprise!!! Metal filings on the magnet!!! I decided to pretend I never saw it and sealed her back up and topped it off with new fluid... Just kidding, now what? I guess I need to rebuild this thing. I need some advice, I really don't have the time or a shop to do this in, this is my busy season at work.
 
crap, I was hoping your problem was going to fix my problem but now we're going in the wrong direction. MY DIFF IS FINE!!!!

ur of no help to me
:)
 
The very first reply in this thread was mine and it still holds true, if this noise is coming from your diff the way I suggested to check it will confirm it.

Metal on the magnet is typical, as long as it doesn't look like a chia pet or has large chunks of metal there is nothing wrong there.
 
Hahaha, Glad I could help k85...
38377k5 the magnet has some metal filings on the bottom third of the magnet, all neatly arranged I'm guessing thanks to the magnetic field, top 2/3's of the magnet is clean. Oil was pretty clean, and there wasn't any debris or metal in the bottom of the housing. However, from the several different layers of paint on the old cover, I'm assuming this things been opened up a few times in it's life... Gears looked surprisingly good, and there's no play up and down, or side to side at the pinion, but when I watch the pinion as the trans is shifted from drive to reverse it will rotate approximately 15 degrees+\-. From underneath it is hard to tell where the noise is coming from, as strange as that sounds, seems to come from transfer case/tailshaft area, but when driving it seems to come from the rear. From the searches I've been doing it would seem that I shouldn't have been able to move the chain invent transfer case, has this thing stretched? I've been looking at JB Conversions rebuild kits, and it seems simple enough, but looks like a full days job to do it right. I guess it's time to just bite the bullet and rebuild the Tcase and the rear, I'm in this truck an unbelievable amount of $$$ already... There's no turning back!!! All in all it's still a great truck, and fun to drive. My first project 4x4, every other truck I've owned was new, I only ever had to change the oil, brakes, and tires. I figure fix all this crap and learn on it before I start lifting and swapping axles etc... I got a thumbs up from another K5 owner yesterday coming home from work, a nice forest green and gold '89 to '91 like mine. It looked really clean and pretty stock. Somebody in Easton is daily driving a M1009 now, I pass him a couple times a week on my commute.
 
Based on what you've said I wouldn't point out the rear end as a failure point right away. From what you describe it sounds further forward in the drivetrain.
 
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