My 2004 started having a strange problem.
It goes into 4x4 fine and comes out fine, however when I accelerate it makes a clunking sound intermittantly. It feels like to me that it is having trouble staying engaged.
Could this be a vacuum problem? It doesnt seem to be that bad of a problem (yet) and the dealer said I have to get a whole new transfer case. I find that hard to believe.

Any experience with a similar problem or any suggestions of what I might be able to do?

Thank you !!



2004 2-door 4WD Manual Tranny

 

Only when you are accelerating? Or also when you are driving? Are you driving on dry pavement? A little more info would be good.

 

Its winter again and the clunking remains. I replaced the vacuum switch on top of the transfer case thinking that it might be the cause but it still makes the clunks.

It makes the slip/clunk sound lightly when just cruising under slight power and the noise and magnitude of the "clunk" will increase drastically as I increase my acceleration. The frequency also seems to increase. That may be just because my speed is increasing.

I have talked with a few people and read the forums but I havent found anything like it.
Isnt there a splined shaft running to the front diff? Could the teeth be worn out (rolled over) from too many engagments/disengagements and it is slipping now?

Thank you!

 

There is a shift collar and associated splined flanges inside the passenger axle tube on the front axle that engage/disengage for 4wd/2wd respectively. When this does not engage, the noise is typically described as a grinding or vibration type noise...

Here is a picture of what it looks like inside the passenger side axle tube:

 

Thanks for your reply.

It doesnt have a grinding sound really, just a clunk in a repetitive manner.
I doesnt clunk at the same speed that I am travelling (relatively) but it still seems rhythmic, like in a circular fashion maybe. When "said" sound occurs it happens in intervals with about a 1 -1.5 second pause inbetween. I picture something spinning and the disruption happening as the damaged area rotates??

When I took it out of 4x4 today I heard a slight knocking as well from below my feet which is something I have never heard before. This makes me think it could be CVs or UJs? They seemed tight but I cant pinpoint.

Thanks!

 

OK,
I had a similar clunk last year with my old T-Case. It sounds simple and basic but try draining your T-Case fluid, and see how much comes out....Save the fluid in a clear bottle and take a look at the sediment in the bottom when it has all settled. Turned out my Blazer was a lease return and it hadnt been serviced...EVER. I had around 200mL of fluid in my T-case and it takes around 1.5 liters..Once I filled the T-case full the clunking went away.

 

I changed all of my fluids (diffs, tranny, t-case) just a while ago and they were all at the proper levels.
There didnt appear to be an abundant amount of shavings in any of them. There were a couple attached to the magnet/drain screw but other than that it was clean.

 

Could the rhythmic clunk be caused by the chain slipping inside of the transfer case?

 

my truck was in the shop for the same problem.......i had a new transfer case put in and the clunk went away.

 

I know its been a while but I have been very busy and have had no time to work on this problem.
I want to document this repair because it is really stumping me and hopefully this will help out someone else.

Last night I pulled out the battery/tray to inspect the vacuum actuator. It looked fine (no rips or tears) but the diaphragm didnt appear to be completely extended (away from the actuator and towards the cable). I wanted to see if the cable was moving freely so I disconnected it from the actuator. As soon as I pulled the clip retaining the cable, POP!!!, the diaphragm sucked all the way down and seated itself against the bowl of the actuator. I was so puzzled because I have been in 2WD for the past 2 months and the vehicle had been off for quite some time. I didnt think the vacuum would still be holding for that long, more so it shouldnt have vacuum at all in 2WD!! I tried to pull the diaphragm back out (to later reinstall the cable) but it was sucked in too tightly to do so. I hooked the battery back up, started the engine pushed the 4HI button and then checked the actuator again. It hadnt moved. I pushed 2HI and checked it again...it hadn't moved!

Well, I wanted to try the vice grip method like swartlkk had mentioned anyway (pull the cable out and lock it in place and check for 4x4/front axle engagement) so I left the cable unattached and rerouted upward toward the battery to grab it with the vice grips.

I reinstalled battery/tray, pulled the cable with pliers and locked it down with vice grips. The cable moved about 1/2" like I was told it would and it felt like it was "moving" the shift fork in the front axle. I started it back up, put it in 4x4 and tried it out. No front wheel power....... I atleast used to get engagement but with clunking under throttle, now I have nothing....

1.Judging by the depth that the diaphragm pulled down under vacuum, am I not pulling the cable far enough? If not, it must take some serious force to pull that fork over.

2. Also, why would the vac line to the actuator not be venting correctly. I replaced the transfer case vacuum switch last year after this problem started but the same symptoms lingered afterward.

I am starting to think that I never got full engagement or disengagement from the front axle, almost like its always been "half-way". This might make sense since the only time that I get the clunk is when I am in 4x4 under power. I wouldnt notice the half-way engagement in 2WD??

Help!!!
I have attached a photo of the actuator which I believe is bottomed-out while the engine is off and in 2WD.