When in 4wd only and especially when I turn the wheel, I get a pronounced clicking noise, about twice per wheel revolution. I thought this was the left CV joint so I replaced the CV axle assembly. Now the clicking noise is not as consistent as before but still there, so was not the CV joint I was hearing.

Now I suspect the clicking is either coming from how the axles locks into place in the differential OR it is the locking ring that locks the front axles to the differential when in 4wd. (Hope that sentence made sense.) I think it is more likely how the axle locks into the differential since in changing the left CV axle the noise has changed a bit.

The clip on the old CV axle appears to be fine. The new CV axle slide in and locked with no problems.

Anyone know where I can find diagrams of the front differential that show the axle locking mechanicals? What do I need to look
for?

UPDATE: I raised the front, in 2wd and can rotate the left and right does not move; rotate right and left does not move.
Put into 4HI, rotate left CW, right rotates CCW; rotate right CW, left rotates CCW....no clicking noise in either direction...of course no load on tires.


At this point I am assuming the left axle needs to come out and remove the cover over the locking mechanicals in order to see what is going on. Not looking forward to this!

Appreciate any insight.

Thanks

 

When 2WD is selected, the right front wheel is isolated from the front differential. It should rotate freely by hand, with very little resistance, and totally independent of the differential. If you rotate either front wheel by hand, the opposite side should not be affected.


In the image below: When you select 4WD, #12 connects #9 to #23.

 

It could be the chain in the transfer case jumping teeth. Drain some of the fluid and check for metal particles. Or remove the fill plug and look inside with a flashlight for damage on the chain.

 

Thanks Captain....yes I have been doing alot more reading and viewing of what goes on when 4wd is selected.

What I have not been able to "see" is what holds the left CV axle in the differential...what does that clip on the end of the axle press against.

I thought it was #23 not being fully mated by #12 due to insufficient movement of the vacuum actuator. But all seems fine there.

But why would turning the wheel cause the clicking noise to start? And why would changing out the left CV axle change the clicking noise pattern?

I think I need to get all four wheels in the air and do more investigating.

Will check-out the T-case as well.

 

There's more resistance on the front driveshaft when the wheels are turned. The new cv shaft rotates smoother than the old one. The T case chain still jumps but not as bad.
I saw a video on you tube recently with a mechanic diagnosing the same problem. "Chevy S-10 No 4x4 / Noisy 4x4" posted by south main auto repair. It's a little long, but very thorough. I don't know how to post a link to it. That should be enough to find it. Maybe someone here with better computer skills could post it on this thread.

 

Rusty Nuts: watched the video and I have nothing like that going on.

So what I did was lift the Blazer, started engine, put into 4wd, shift into D....and I was able to hear a ting...ting....ting.....which appears to be coming from the rear joint of the front driveshaft. Guess it is time to replace the CV joint.

Only one I have found is Dorman 932-101 for $110.00

Anyone use this? Any good? Is there a better one? Not like I use 4wd much, so probably alright for my use.

 

Here is the link - A good video/

 

Yep, I agree...pretty good video that shows the vacuum actuator and what happens when the 4wd is engaged. Not a pretty sight of the oil coming out of the t-case though....lots of metal particles.

Again I have nothing that severe going-on...and I think I found the problem to be the CV joint on the front driveshaft. Just have not done anything about it yet.