loud unkown clunk or pop after towing. front axle?

[thinger2]

So if you put it in gear and driving slowly forward you get the thump noise?
Or only when turning?
Are you sure its not hanging in 4x4?

 

[williscr3]

so i did the transfer case yesterday, filled it with fluid today. had someone else start it and just by pure chance it made the noise during start up with me standing next to it sounds like a backfire but after, like out the exhaust instead of through intake. today i noticed it has a bit of a stumble if i softly accelerate and then if i pull out quickly it does it. so maybe i have a weak coil or something? kind of explains why it sounds like its in the back end. i have dual exhausts straight out the back. whats weird though, if it put it in park and rev it, i get no noise just light stumble. only under load it pops. i cant remember if i put new plugs in the motor during the swap. im sure i did, i ended up going through 3 sets of plug wires because they kept burning off the exhaust. i bought high temp plug wires and fiberglass sleeves for it and its been fine. they look ok so i wouldnt think plugs or wires. sadly, my spotter said this from the beginning while i was backing up. since she was a bad spotter while backing up the boat, being sidetracked by the butterfly in her flowers, i didnt believe her lol. specially since it doesnt sound like a backfire.

 

[thinger2]

so i did the transfer case yesterday, filled it with fluid today. had someone else start it and just by pure chance it made the noise during start up with me standing next to it sounds like a backfire but after, like out the exhaust instead of through intake. today i noticed it has a bit of a stumble if i softly accelerate and then if i pull out quickly it does it. so maybe i have a weak coil or something? kind of explains why it sounds like its in the back end. i have dual exhausts straight out the back. whats weird though, if it put it in park and rev it, i get no noise just light stumble. only under load it pops. i cant remember if i put new plugs in the motor during the swap. im sure i did, i ended up going through 3 sets of plug wires because they kept burning off the exhaust. i bought high temp plug wires and fiberglass sleeves for it and its been fine. they look ok so i wouldnt think plugs or wires. sadly, my spotter said this from the beginning while i was backing up. since she was a bad spotter while backing up the boat, being sidetracked by the butterfly in her flowers, i didnt believe her lol. specially since it doesnt sound like a backfire.

Oof! dont feel bad my friend. I did almost the exact same before.
Many years ago I convinced myself that I had a bad transfer case on my K5
Got another one from the boneyard, pulled the old one and dumped transmission fluid all over my head and my friends squeeky clean driveway.
Put the new one in and nope,
It was the transmission
That was in Phoenix in August
It was 105 that day.
Got it all back together and about two weeks later, it starting making a wierd groaning sound but only when I hit a big bump.
Out of an abundance of paranoia, I searched high and low and crawled all over under that thing.
Could not find it.
It was a malfunction purple Barney the talking dinosaur stuck under the passenger seat.
The noise was Barney trying to sing "I love you, you love me...
Barney got drug out in the desert and shot

 

[williscr3]

Lol sorry to laugh but that is hilarious. Its funny how you get used to it always being the worst case scenario and then when it actually isn't for once you still go to the extreme.

I'm still not out of the water yet I guess. I'm going to investigate plugs, wires and coils. Hopefully one of them is faulty. Tonight after work ill try to pull it all off, inspect and test. Thanks for a good laugh.

 

[Ben Burrage]

Do you still have factory poppet style injectors? I chased noise for years, and stumble. Did intake gaskets twice, wires and plugs several times. Finally bit the bullet and upgraded spider to newer MFPI. What a difference! No stumble, and increase inpin Also did big 3 upgrade, and cleaned/replaced all grounds. Not sure what exactly fixed it but upgrades were much needed. Also upgraded to AD244 alternator. Hope this helps...

 

[Schurkey]

MY first guess would be a partially-failed thermal actuator on the front axle.

Does a '96 HAVE a thermal actuator? My '88 does, my '97 doesn't.

Anyway, if the TA is weak, it doesn't fully engage the front axle, under stress it might pop in and out of engagement.

Easy to check. Disconnect wire, unscrew the actuator from the axle housing, connect wire, have someone shift into 4wd while you watch the ***** inflate.

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I had a worn-out transfer case that would pop out of 4wd--but it only popped out, once. Not multiple times.

 

[williscr3]

sorry for the delay. just finished up with work. poppet injectors were replaced with the upgraded ones couple years ago and then i LS swapped it so im running a 5.3L now. so turned out the 4wd actuator wasnt plugged in because the wire was shredded. i fixed that. the transfer case did not fix the problem. the actual problem was the spark plugs. 1 was cracked. i swapped them and it runs like a champ again. 2 of my plug boots melted a little bit. thanks for all the great suggestions and help.

 

[thinger2]

sorry for the delay. just finished up with work. poppet injectors were replaced with the upgraded ones couple years ago and then i LS swapped it so im running a 5.3L now. so turned out the 4wd actuator wasnt plugged in because the wire was shredded. i fixed that. the transfer case did not fix the problem. the actual problem was the spark plugs. 1 was cracked. i swapped them and it runs like a champ again. 2 of my plug boots melted a little bit. thanks for all the great suggestions and help.

Awesome! the plug wires on these are a pain.
I think I have about 20 Moroso wire clips on mine and changed a few of them to straight boots trying to keep them from getting cooked

 

[williscr3]

i put the metal plug boot covers back on, and then slid the fiberglass tubes over it and still burned 2. these headers are becoming a pain. just the way they turn up then down then across to the next cylinder. im running the factory coils and i think i bought 12" plug wires. im wondering if i can get away with the 9" ones. that might make it less messy and lessen the chances of burning. drove the truck around again today and no noise. i cant believe it. in the truck, the noise it made, i swear i broke my axle. it made the same sound as last time i broke an axle in my wrangler. thanks again everyone for suggestions.

 

[Kevco2]

Does a '96 HAVE a thermal actuator? My '88 does, my '97 doesn't.

Sorry to kinda hijack this thread
BUT do you know if having the electronic actuator on my 1997 Suburban makes my front diff a 1st or 2nd design?
I need to replace worn axle bearings and mid-97 was apparently split production
The different designs do not use the same size bearings and seals

Thanks

P.S. I made a specific thread about it just this morning if you would rather add any info over there