Need help to diagnose drivetrain noise

[02expltd]

Hello all,

I have been a member here for awhile and usually I can get my answers by searching, but now I need some direct help.

I have a 2002 LTDV8 with selectable 4hi, 4lo, and auto 4wd. It has approx 105000 miles on it.

I will try to describe the issue as best as I can. (sorry if it is long winded)

In the past week I have noticed some noise coming from the drivetrain. I am not sure exactly where it is coming from but it feels like it is from the driveshaft all the way up to transfer case to the front left wheel.

Today it got much worse, I was driving on the highway and pulled of at my exit, as soon as came off the gas it started to shutter, as I slowed down to a stop it got louder and there was a thump, thump, thump every second, followed by sort of a screaching noise on the front left wheel.

After I came to a stop, pulled away accelerating it went away, as soon as took my foot of the gas at around 40mph the noises would come back until I came to a stop. It seems that whenever I take my foot of the gas it will start again. I can manipulate it everytime. (I know it sounds weird)

The tranny shifts smoothly even when the noise is there, there is no warning lights coming on, so I doubt that is the problem.

All of this occours in auto 4wd, but the noise is still there if I switch it to 4HI after the noise appears.

some more notes on the truck
Brand new brakes all around a month ago along with a front left wheel bearing.

I also have the spare tire on the left front wheel, which is slightly smaller then the other tires, My new tire is coming in tomorrrow and being installed.
Now that I think about it, the noise didn't start until after the spare went on last week. Could this have anything to do with it?
IF so, then could it have escalted to a bigger problem now?

Any help would be greatly appreciated, sorry again for the long post, but I was trying to describe the condition as in depth as possible.

oh and after searching for a while, i have noticed that some members are having problems with the 4x4 module, does this sound like the culprit?

thanks in advance.

 

[btexpress]

Different circumference tires can reek havoc on the differential. If the noise didn't start until you put the spare on then this is the area I would be looking at. Especially on AWD vehicles this can be a big problem. See how it operates with the regular tire before anything else.

Of course since you just had work done on the side you think the noise is, might be a good idea to recheck the work.

 

[02expltd]

Well, after 2 days of driving on the new tire, the noises have not come back. I guess that was the problem. I never would have guessed that having a slighlty smaller tire would have done that. The spare was a 245/70/16 and the others are 245/75/16. A leason learned I guess.

 

[capewelr]

tyre diameter

As I posted elsewhere, only 1/4 inch difference in tyre diameter can cause 4 wheel drive to automatically engage. The diff is then trying to make up difference in number of rotations the tyres are making per mile. In the dry this will tear the diff apart.