Front end POPing noise when in 4x4 under load.

gofast505 · Post by **gofast505** » Wed Feb 18, 2009 10:36 pm

So I put my truck in 4x4, I get the constant light and my truck is in fact in 4x4, but under a load, like climbing over a pass, or up my driveway I hear a ping or pop every once in a while. The you can feel this in the entire truck too, feels like maybe a slight slip even. Where should I start? T-Case? Front axle? CV's?

24digger · Post by **24digger** » Thu Feb 19, 2009 4:13 am

Tortion bar mounts possibly.

roadrunner · Post by **roadrunner** » Thu Feb 19, 2009 6:06 pm

Transfer case chain slipping? (I think we have one in the NP233 case if that's which one you have) Bad CV axle? (likely the fronts) Bad splines on front driveshaft? (Not very likely) Extremely badly rusted universal joints in front drive line? Bad/failing front differential gears? The list could go on but this more than plenty to check to start with.

gofast505 · Post by **gofast505** » Thu Feb 19, 2009 8:13 pm

Is that all?

I had to drive over berthoud pass last night, it def start slipping, and almost sounded like the ping was bouncing back and forth between sides.

Least I have the truck finally paid off.

roadrunner · Post by **roadrunner** » Fri Feb 20, 2009 5:38 pm

We need a little more info. Is the noise emanating from the front, rear, center of the truck? Is this pass you're going over and your driveway on a slight curve as well as an incline? I tried to put those things I mentioned in order I would suspect but it is difficult without being there and hearing it.

Post by **HenryJ** » Fri Feb 20, 2009 5:52 pm

Lube the T-bar sockets.

blaz · Post by **blaz** » Fri Feb 20, 2009 8:50 pm

HenryJ wrote:Lube the T-bar sockets.

What is the prefered lube?

Post by **HenryJ** » Fri Feb 20, 2009 9:01 pm

I use GM Superlube now. Some use an aerosol white grease. Fluid Film is good.

You want something that will penetrate. Not a nut breaker or cutting fluid though. It needs to stick and not drawing dirt is a good thing. WD40 evaporates and would not be the best choice.

smallblocker · Post by **smallblocker** » Sat Feb 21, 2009 11:31 pm

By slipping, do you mean your 4wd stops working intermitenly?

roadrunner · Post by **roadrunner** » Sun Feb 22, 2009 1:08 pm

smallblocker wrote:By slipping, do you mean your 4wd stops working intermitenly?

Not exactly. If you have a chain drive running on metal gears what I mean is the chain is jumping or "slipping" under load allowing unintended chattering which can be heard and felt in the cab, as best I can describe it, as a shudder and heard as a popping or clunking noise. In severe cases it will sound very metallic and clang loudly. This was a common problem in older 4x4s back in the mid/late 70's and 80's. Usually you could replace the chain in the T-case once or maybe twice then you had to replace as a chain and gear set which was pretty pricey even back then. Think of it this way: each link in a chain has a wear point where it hooks to the next. With dozens of connection points it doesn't take much wear to add up to slack which will allow the chain to jump or "slip" causing the problems I just described usually under a binding load such as an incline or a turn while in 4x4.

Post by **HenryJ** » Sun Feb 22, 2009 2:00 pm

It has been my experience that the transfercase chain does not tend to slip or jump as it has really good retention characteristics. It is possible that a chain could slap or rub the case. I have not seen much of that either.
Bearing noise I have seen a few times. A broken case and the resulting mess of scattered parts a few times.

Personally, I would put other suspects ahead of transfercase problems.

roadrunner · Post by **roadrunner** » Sun Feb 22, 2009 5:45 pm

Yes, a transfer case chain will jump when worn. I have replaced many in my wrenching days. Some even still under factory warranty. They acted and sounded as I described above. Once you experience it you will never forget how it acts and sounds.

Post by **HenryJ** » Sun Feb 22, 2009 6:24 pm

I am sure it is possible. I also think there would be symptoms more than just a popping sound ocasionally.
My thought is that there are simpler suspects that would be more likely.

K.I.S.S. - Rule out the easy stuff first.

Steventruck · Post by **Steventruck** » Fri Apr 17, 2009 5:11 pm

My ZR2 is doing this too. I first assumed that it was the front axle actuator, so I swaped in the Bravada 1-piece axle shaft and tube. Also inspected front drive shaft and U-joint, all is good.

Problem still exists...

so I figured maybe it was the front ring/pinion jumping teeth, so I re-installed the iron front pig (I had an issue and needed a replacement pig while my iron one was being fixed, so I bopught an aluminum one). While I was in there and had everything apart, I also replaced the RH CV axle and inspected the LH one.

Prolem still exists...

So I bought another NP233 from the junkyard. The transfer case is the only thing left, as there is no noise in 2WD. I thought very seriously about doing the NP231 swap (manually shifted) but the junkyard wanted three times as much for that case ($450 vs. $150) so I went with direct replacement. I'll install the replacement soon.

Steve