Took out the nv149 put in the stock 4482 bw case and my popping noise went away. So I guess it needs a new viscous couple.

I just need to decide if I want to stay awd or go push button 4wd. What would you do?

 

On one hand I'm glad you found the source of your noise, but on the other I'm sorry for the evident issues you've had with the 149. It's rare they have any failures even in high powered vehicles, which is pretty remarkable considering they were always installed in heavy extended or crew-cab trucks and SUV's. Most viscous coupler issues can be traced back to misuse due to heat build-up from lack of servicing, running a single driveshaft and/or allowing the transfer-case to operate in a hump mode for an extended amount of time. Basically heat is the factor in the demise of the coupler in just about all cases and while you know how the unit has been treated since you’ve had it installed, who knows its previous history, that and of course anything mechanical can fail. The only other reasonably common failure, which is unrelated to your condition, is the oil-pump plate wearing through the rear case half. I really was rooting for you finding the source of your issues, and while you’ve narrowed it down considerably, I still hope eventually you’re given the opportunity to pin point the source.

 

Well when I got it the Intire inside of the case was black and a lot of bearing rusted. I used an old auto track case for bearings. I changed oil every few thousand miles for a while. I also over filled it by half quart or so for better cooling. It's performed great. Hell even now I could go in the sand and mud and it performed great besides the popping. But my front tires were wore more than my rear so I wonder if that cause problems. But i do know that the case was bad looking. The rear case half was toaste. The rear bearing was shot and the drive shaft wore into the housing itself. This was befor I got it.


I also wonder if the front can handle more power with my weight. I want to up the anti soon

 

For the front axle, beings the power is split between the two axles, the little 8.25” unit seems to hang in there for most people. We all see the common bearing failures and related issues, but not right out gear or axle failures. It seems as if the CV’s are actually the fusible link in the ½ Ton front ends. That and of course with the aftermarket deeming the 8.25” so weak that they don’t offer a better carrier that would provide any additional traction capabilities. Chase and I have spoke about this before, but really couldn't decide if it was worth it, where it has been talked about in the past of swapping in the 9.25” from a ¾ or 1 Ton, but it’s not a direct bolt-in and would take some work. People have done it in a few 4WD applications, mostly when also trying to make a switch to an 8-Lug hub assembly, but the CV splines do match the ½ Tons 6-Lug hubs and should make the switch slightly easier. Of course all the typical 9.25” units have the selectable style components with a two-piece passenger side axle unlike our AWD counterparts. There was an AWD version available in the Hummer, however it has a goofy mounting point for the passenger side axle tube and I haven’t a clue as to the length of its axle shaft. If it was the proper length to be used with a standard 4WD axle tube, one could just build a block-off plate for the encoder motor. Besides just being plain beefier and not really hearing of bearing failures like you do with the 8.25” units, the 9.25” models offer the availability of upgrading to an aftermarket carrier such as a TruTrac, E-Locker or others along those lines. Of course you probably wouldn’t want to drive around with the front locked for handling and durability reasons, but for straight line use it should be an asset.

 

Mine had the bearing failure around 80,000 miles. So that's not too bad I guess. And I have life time warranty axles from autozone so if I break one that's a cheap fix. But man it would be nice to be able to lock that dude up. I've seen some people try the 9.25 swap on gm full size forum. However I never seen one get done. I love my awd because I can just get in and drive. No matter rain, mud, sand or snow I just get in and go. But my stock case uses the brakes to transfer power and that horrible for what we do. It induces torque steer. I really really liked the 149, I guess I'm just afraid if I throw in a new viscous coupler that it will go bad again.

How important is it for tire height to be perfect all around? I run 40 psi in all the tires should I have a little less in the back tires? Should they have more if I tow with heavy tongue weight? These are the things I don't know and never thought about before. I found a site that sells the coupler but they tell you to measure your tire heights and that it's detrimental to the coupler if they are not with in 1/8" or so.

 

From my understanding it is important for the tire height to match front to rear and has been discussed many times on the Denali site, with a good deal of people running staggered pressures due to the extra weight over the nose. Some even feel it’s better to replace all four tires at a time, something that I’ve not necessarily done in the past and didn’t have any issues. I’m of the opinion that there is no way to keep it perfect and even the spare GM supplied didn’t match perfectly in height, but they also didn’t intend you to drive it extended amounts of time or speed in some cases with the spare installed. In short, I would do my best to keep the tire heights the same, except where I knew that I wouldn’t have to drive extended amounts of time at highway speeds causing the viscous coupler to overheat. Even though I feel these units are pretty tuff, I do keep a spare on hand just in case and even a spare front diff and CV axles just in case.

 

I may have to check out this site and see if I can find the threads. I just happened to have replaced all 4 tires yesterday went with the stock ls2 tires. If they can hook well enough to break an axle then I'll stick with them. I wish I had a spare. I can't seem to even find the damn coupler.
Would rock auto have them?

 

The Viscous Coupler List for $824.35 new from the dealer. Some other places have it marked up in the $900 range. You would be better off finding another good used unit. I have seen them as low as $400 and as high as $800 used locally. Some places ask upwards of $1000 used...

You can get a re-manufactured unit through the dealer for around $1500 list price with a warranty. When I called around it was just as much for someone to go through it as long as it didn't need any major parts. I guess it only included bearings seals and a new chain Kit plus labor.

If you get a discount at the dealer even better!!!

 

i just had one hell of an idea. we need to talk a company into making a drop in torsen diff to replace the viscous coupler. surely it wouldn't be too hard to do. if it cost around the same as the viscous type and was stronger ie, wouldn't over heat. it would be well worth it.

 

Never hurts to ask! They already make an aftermarket case half to replace the factory one that gets worn through... Contact some one and lets see what happens.