Big Loud Bang in 4X4 only

[Electromag]

In 4x4 my 1991 F350 has been squeaking for years, I finally figured it out and decided to take care of it. The front drive shaft was squeaking right at the Transfer case end. I was going to push the u-joints out myself but I discovered something that I never seen before. There is a ball and joint in between two u-joints right at the transfer case. Its called a double cardan joint according to my shop manual.
So I took it to the people that know,,, "AZ Drive Shaft".. A day later I picked it up with its new sticky black paint and installed it into my truck. All looked well, and it spun freely without the hubs locked in.

I went out in the desert and needed to back up in some soft sand. I put it in 4x4 and in reverse. Backed up maybe 20 feet on flat surface in the dirt and then I heard this huge bang. I got out thinking that I just dropped my new drive shaft. But everything looked fine, So I drove it forward about 50 feet (in 4x4) KaBang! Again!

I stopped again and looked it over, hung my head out with door open and drove it a couple of feet. Again I couldn't find any problems. Drove it about 200 yards and then it did it again Kabang! At this point I was pretty worried being way out in the desert so I took it out of 4WD, unlocked the hubs and drove it home with no further problems. Got it home and drove it around with the hubs locked in... No problems... Jacked it up and put it on 4 jack stands, turned all tires brakes on brakes off, got it up to 60MPH in 4x4 with the hubs locked in, cant duplicate it. Took it down a dirt road for 2 miles in 4x4H and 4x4L up hill and down, still cant duplicate.
Never had this problem before I replaced the drive shaft. What to do? Drive it until it breaks? Any and all suggestions appreciated. Would a U-joint do this?

Tony

 

[Roland_Jenkins]

Transfercase chain is stretched is my guess.

 

[subway]

Transfercase chain is stretched is my guess.

yea my truck does it to sometimes when i am loaded down and pushing it in 4x4. like when i am going up a hill in deeper snow or bogged in the sand. it never does it in light 4 wheeling. i figure i will be rebuilding the transfercase in my spare time.........just never get spare time.

 

[Electromag]

It did this driving down a flat dirt road and has never done this before.

 

[subway]

hhhmmm how are the u-joints inside your steering knuckles?

 

[biggin92]

i can almost guarantee your hubs are going bad

 

[Electromag]

It had to been somthing up with that double cardan joint that I replaced. It only happened when I put it in 4x4 with this new rebuilt axle. I have had it out a few times and havent had any problems like that since that day when it was new. I hope that it never comes back!.


now 2000 miles later, still no problems in 4x4.