hey guys, I have been battling and wasting time/money on this darn vehicle, its a 05 jimmy 4auto. This is the summary 40 hours later

• The symptoms are as followed:

1. clicking when driving with 4hi/4auto/4lo engaged
2. the clicking is extremely loud/noticable under LOAD
3. if I coast downhill under NO LOAD or NEUTRAL, no noises (99% less)
4. If I unplug the vacuum switch on the firewall for the front actuator, the 4hi or 4auto light blinks, and there is NO clicking. The transfer case in 4hi/lo when this happens, just no locked hubs in the front

• The troubleshooting is as followed:

1. I Initially thought it was the front differential carrier (Dorman part number 600-561), replaced it, did not fix my problem
2. I have checked the transfer case - firewall switch vacuum (good, 500mm Hg or 10 psi)
3. I have checked the 4wd plunger actuator vacuum (good, 500mm Hg or 10 psi)
4. I have checked the function of the front plunger, leaks, pulling force, as well as the cable condition - GOOD!
5. Using a stethoscope (screwdriver), the noise is definitely in the front differential
6. U joint at front dif - OK
7. CVs passenger and driver appear OK

So, there you guys have it. I'm open to ideas. Its peculiar when it makes noise, never in 2wd, only in 4wd, and only under load, also doesn't make noise when the passenger front CV isn't engaged.


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Sounds like you need to pull the differential extension housing off the passenger side of the front diff and have a look at the 4wd engagement sleeve & gear inside.

If the gear on the outer driveshaft looks like the image below, you'll need to replace this gear and the engagement sleeve. THIS POST in the Tech Article section has the part numbers involved.

Notice the wear to the teeth on this gear and the material that has rolled over the edges of the teeth. This material will prohibit the sleeve from properly sliding over the teeth which is what needs to happen to properly engage the front axle.

*Moving to 2nd Gen Tech*

 

So what is the cause for the gear being worn like that? The vacuum that pulls on the cable being insufficient?

 

There are a number of things that can cause wear on these components; insufficient vacuum, restricted cable movement, and/or broken return spring inside the front axle to name a few. All that it takes is a little bit of rubbing left undetected/unrepaired and it snowballs from there.

 

Hey man, thanks for the response. If you look at my troubleshooting, I actually replaced this part under step #1, I was surprised it didn't fix it

Any other ideas? Hopefully not front dif..... Any way to narrow it down before I spent time ripping things apart?

 

Something else you may want to check to make sure,
Take the fill plug out of your transfer case and see how much slack is in the chain.
I have seen a few transfer cases stretch the chain enough to start jumping teeth and sound the same as the front diff issues.
Skip to minute 46 of this video and you will see what im talking about.

 

Your step #1 lists the "differential carrier" which to me is what holds the ring gear so I dismissed it. Admittedly, I didn't look up the part number listed.

If that's what you replaced...did you also replace the collar that engages this gear? If not, did you verify that the old collar it would easily slip over the new gear? There should be a slight bevel to the teeth on the corresponding sides of the gear and collar to aid in engagement. If I remember correctly, the collar is bevelled on only one side and needs to be installed with the bevelled edges pointing away from the differential (towards the gear you replaced).

I would also state that I have seen a number of people have issues with this particular Dorman part not having the correct bevels on the engagement side of the gear which can lead to premature failure. The GM gear & collar have all of the correct features. They cost more, but if it's the difference between replacing them once versus multiple times, I'd rather spend the money.

 

I do not suspect this is the issue, below is why:

1) So there is absolutely ZERO noise when the transfer case is in 4hi / 4lo, when the front hubs are unlocked (disconnect vacuum line to cable actuator in front dif)
2) using my screwdriver stethoscope, the noise is audibly in the front dif

The collar for engagement was not replaced. It appeared fine with no scoring or damage, and the beveled edges were facing the passenger side away from the differential - CHECK


Any other suggestions guys? Is there anything that could point towards the front dif itself? I find it curious that the noise is only evident when the front passenger axle shaft is engaged....

 

Ok guys, I fixed it. For those of you who care

1) I thought the noise was in the front dif. No noise in 2wd, and no noise in 4hi with front actuator disengaged, therefore it MUST be the carrier - I WAS WRONG
2) After listening very very closely, it does make noise in 2wd
3) it also makes noise in 4hi with front actuator disengaged
4) and also makes noise with 4hi front actuator engaged

The noise is by far the most audible in situation #4 because everything is under load, but, #2 and #3 are still there, just very faint.

I used a screwdriver on my ear to listen to the front dif and that's where I THOUGHT I heard it. I put the screwdriver on the transfer case, and heard it some more. In situation #2 and #3, still in the transfer case, just quiet.

I thought for sure my transfer case was pooched, but I remembered that last year I purchased a front driveshaft CV joint that hooks the front driveshaft to the transfer case, and never replaced it because I couldnt get the exhaust crossover bolts off (FACEPALM!!!!!!!!)

Well, this joint is completely FU**ED, and Its my stupid *** fault for forgetting about it. I thought my diagnosis was bulletproof and I went ahead ripping the front dif apart like an idiot, so its my fault and lesson learned. I hope this helps someone in the future. You may think you are right, but you usually aren't.

Thanks for those of you who replied.

 

Thanks for the update. We've all been there thinking we have our diagnosis dialed-in but nope! These follow-up type posts are some of the most valuable. By sharing this we up you've earned lots of karma for the next challenge with your Blazer!