Transfer case may be busted

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BoostedGMC

Guest
I am getting a loud clunking/poping noise. The pop is just like this truck. Listen to it at 4 seconds into the video. http://videos.streetfire.net/video/GMC-Typhoon-vs-Chevrolet_73617.htm. The clunking seems like the chain is slipping. it only does this under a heavy load. I can't find a video of this but I'll try to borrow a video camera and post the video. I removed the propshaft and the noise went away. The u-joints seem to be in good condition. I may take a trip to the junk yard tomorrow and look for a used one to swap but just to make sure I get the right one, a 1990-98 astro/safari and 1991-97 bravada will work? Almost forgot, its a Typhoon I will be putting the transfer case in.
 
Trapper

Trapper

New member
Re: Transfer case may be busted

I think the Typhoon has the same one in the Bravada different out put tooth count I think.
 
willyson

willyson

trollin'
Re: Transfer case may be busted

are you sure youre not talking about the front differential? i think the transfer case is rotating no matter what
 
B

BoostedGMC

Guest
Re: Transfer case may be busted

Yeah I mean transfer case. The sound is coming fron the center of the truck. I thought maybe the chain is jumping the teeth in the transfer case while under a heavy load.

I am going to take a ride to my buddies house and see if I can get a video camera to get this sound on camera. Hopefully I can post it tonight.
 
DaveP

DaveP

Active member
Re: Transfer case may be busted

Viscious clutch is binding. You confirmed it by removing the front driveline, and it went away.
 
cloneman315

cloneman315

Active member
Re: Transfer case may be busted

the sound is a hard sound,once it builds about 10psi when driving you hear it or hard start.
 
B

BoostedGMC

Guest
Re: Transfer case may be busted

Just got a video camera and got the sound on tape but am having trouble getting it to import to my computer. I'll have it on here tomorrow. Thanks Dave, hopefully this sound will match the sound of a binding clutch.
 
cloneman315

cloneman315

Active member
Re: Transfer case may be busted

i remember there being a way to check the clutch,it has been a few years though anyone remeber?something with breaker bars on both ends etc
 
B

BoostedGMC

Guest
Re: Transfer case may be busted

I had thought at first it was my axles, so I bought two brand new axles. I didn't install them yet. Maybe I will replace them before I swap the transfer case.

If I do end up replacing the case, I will be looking for a 1990-98 astro/safari or 1991-97 bravada? Will the numbers match my ty transfer case?
 
DaveP

DaveP

Active member
Re: Transfer case may be busted

BoostedGMC said:
If I do end up replacing the case, I will be looking for a 1990-98 astro/safari or 1991-97 bravada? Will the numbers match my ty transfer case?
Click to expand...
90-91 Astro/Safari, and 91 Bravada have the same rear output spline and seal diameter as Syclone.

Here's a Ty on left. Sy on right.
549ea69b.jpg

If you get a 92-up T-case, you can transfer the Ty output yoke to your Sy drive shaft. Don't need to change the entire drive shaft. 1994 Bravada uses a larger front-output shaft bolt circle. You can transfer the flange from your Sy case.

Be cautious when buying used 4472 T-cases. The one you're about to buy is just as old, and may be just as messed-up, as the one your replacing. I haven't found a used T-case with a good V-clutch in years. If the vehicle your getting the case from doesn't have the front driveline in it, the V-clutch is probably locked up. That's why the shaft is out of it. VERY common, now. BEWARE!
 
B

BoostedGMC

Guest
Re: Transfer case may be busted

I have a typhoon...I guess I'd be better off rebuilding the case instead of possibly wasting time installing a case worse than mine.
 
George Blake

George Blake

DONATING MEMBER
Re: Transfer case may be busted

Let me know if you need anything. I have most everything here to rebuild it.
The viscous clutches are expensive but need to be replaced in anything with over 60K. The steels inside wear off and contaminate the viscous fluid and they don't work properly anymore.
Because they are expensive though, this usually gets skipped.
The case I'm doing for Mr Hacking had a popped viscous in it and a missing thrust washer. Good stuff.
 
cloneman315

cloneman315

Active member
Re: Transfer case may be busted

george since i am going to be helping him rebuild this,what is the total cost of what you think we should replace,not sure on the clutch,i thought there was a way to test it with breaker bars or something but could be wrong,it does not seem like when you launch the truck that the back wheels really break lose which means the clutch could be ok ,but not 100% sure
 
George Blake

George Blake

DONATING MEMBER
Re: Transfer case may be busted

Tear it apart.
If it's got over 60K, replace the viscous.
Check pinions in the planetary, if they are loose, (most are) replace the planet.
Chain, seals, bearings, thrust washers, and bushings. It'll be like new.
See what you need and tell me, I'll get you a price.
 
George Blake

George Blake

DONATING MEMBER
Re: Transfer case may be busted

Complete teardown and rebuild here:
http://www.primegears.net/gallery/BW4472-rebuild
To get the viscous off the sun gear shaft, put a bushing driver with a bolt and nut in the center so it has something to spin on and just pull the bearing off the end of the shaft. Spacer cog,spacer, viscous all slide off after that. Reinstall in same order, use bushing driver or press to tap/press the bearing back on. Use a NEW bearing or it may just fall back off. Make sure you use the CORRECT bearing as well. Some are close in tolerance but can't be mixed.
 
cloneman315

cloneman315

Active member
Re: Transfer case may be busted

so george if we decide to put a used one in while he saves to rebuild his,what trucks have them ?
 
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