Clank at font of Vehicle when accelerating from a stop 4x4

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

brcknrdg Rob

Well-Known Member
Joined
Nov 4, 2019
Posts
46
Reaction score
5
Location
Ventura Ca
So...On our 09 4x4 Xlt 5.4, we have a clanking sound that is coming from the front end. IT sounds a bit like when a UV joint is loose as the driveshaft turns and torque is applied. The difference being that it does not make the sound until it has been driven 25 to 50 ft. and the noise has graduated from a clank to a clankity clank clank. Then when slowing back down and coming to a stop 25 to 50 ft from stopping it clanks again. I have all new Brake pads and rotors all the way around and the caliper pins were well serviced. This eliminates a caliper clap.
I feel like it is coming from the driver side of the axle/differential and that it has something to do with the vacuum lock not engaging/disengaging properly. Unfortunately I have been reluctant to by the second set of jack stands required to lift the whole thing off of the ground so that I could hear it and locate it while the vehicle was in drive and the vacuum is enacted to disengage the axles(my understanding of proper function for the system). So today at lunch I decided to take it to a shop to have them diagnose it on a lift. For some unknown damn reason, location maybe, or seeing the sign, or just pure ignorance, I ended up at MIDAS of all damn places.

After maybe 15 min they had driven it around the block a few times and hoisted her up. They called me into the service area to explain why they would need another $400 on top of the $79 to go any farther with the troubleshooting. The tech whom I later found out was the owner of the franchise or so he claimed, said that he was able to diagnose that it was coming from the differential by removing the front axle coming from the transfer case. It was at this moment I should have told him to drop it back on the ground so that I could leave. I didnt though because I was still in awe as to how he was able to do that in such a short time period and without handprints or tool markings. He then proceeded to tell me that he was going to need to "remove the pumpkin" to go to the second level diagnosis. I then asked if he was going to remove the differential cover and he replied that yes he was "going to remove the pumpkin". Why did I not walk away? Well I placed my hand on the tire and noticed that it free spun without the engine running. I then asked him how that was possible without the engine running and he explained it was because he had disconnected the axle. After a brief discussion of nuts bolts and theories I then discovered that this was done by means of the computer where in I asked if it was possible to lock it out as I did not have the inclination to start the removal of the "pumpkin" at this time (at Midas). He then informed me it was not allowed and I asked again if it is possible and that I am not asking him to do it since I would not want him to go against policy and he again claimed he wouldnt and I stated I wasn't asking and this went on like a damn laurel and hardy sketch until I kindly asked him to return my vehicle to me.

Here is the Question(s);

Is it possible that this is a lack of vacuum power due to a leak somewhere preventing complete disengagement until higher RPM's are achieved? If not is it possible for a differential to make a one off noise that is not increased in occurrence per revolution? If so what part in the differential might that be?
Should I go some place to have the differential serviced or would they just pump the fluid since the cover is burdensome to remove?

Side note: The last time I had 4 wheel drive engaged it worked fine, however it did make a grining noise/feeling when making a right turn with the drivers wheel on an incline


I will most likely be taking this one to a professional but I like to understand things and not just names of parts.
 

grdsman

Full Access Members
Joined
Sep 8, 2019
Posts
82
Reaction score
30
Location
Colorado Springs
There should be no reason to suspect the differential is making noise while driving due to the fact that the hubs should be disengaged, thereby not touching the diff. I would start by seeing if the sound goes away in 4WD. You could also test it by disconnecting the vacuum line at the solenoid to allow the hubs to engage without being in 4WD. If either of these cases eliminates the noise, you either have a bad IWE, a bad vacuum check valve or a bad solenoid. If that doesn’t eliminate the sound, then you have something else going on in the hub area most likely. My money is on the vacuum.


Sent from my iPhone using Tapatalk
 
OP
OP
brcknrdg Rob

brcknrdg Rob

Well-Known Member
Joined
Nov 4, 2019
Posts
46
Reaction score
5
Location
Ventura Ca
There should be no reason to suspect the differential is making noise while driving due to the fact that the hubs should be disengaged, thereby not touching the diff. I would start by seeing if the sound goes away in 4WD. You could also test it by disconnecting the vacuum line at the solenoid to allow the hubs to engage without being in 4WD. If either of these cases eliminates the noise, you either have a bad IWE, a bad vacuum check valve or a bad solenoid. If that doesn’t eliminate the sound, then you have something else going on in the hub area most likely. My money is on the vacuum.


Sent from my iPhone using Tapatalk
That is my understanding of the system as well, Thanks, I was thinking about it this morning and I should just drive around a big dirt lot in 4 and see if it makes the sound.
 

Dustin Gebhardt

Full Access Members
Joined
May 10, 2018
Posts
122
Reaction score
55
Location
Tulsa, OK
I had a similar clunk noise around 35mph, particularly if I gave it slightly more throttle than normal. It turned out that I had a vacuum leak in my IWE system, specifically in the rubber adapter sitting right in front of the first crossmember. I replaced it with a new one and my issue went away. There are several posts here and on the internet on how to diagnose IWE issues. First, see if the issue goes away when you run in 2H mode. In 2H, no vacuum should be applied to the system, so it shouldn't make any noise if/when a change in the vacuum force changes.
 

Forum statistics

Threads
53,391
Posts
500,598
Members
46,798
Latest member
geovanni
Top