Front driveshaft U-joint grenaded today - searching for cause?

[coinball]

Driving over to my g/f's house today the U-joint between the front driveshaft and transfer case decided to fly apart...well half of it did anyway. The U-joint was pretty rusted so it most likely needed replaced.

I'm wondering if the front diff is to blame; I had recently used 4wd to drive around in my backyard (testing the 4wd for the first time since I purchased the vehicle) but everything was fine, no abnormal noises or vibrations. I just changed the front and rear diffs over to synthetic 75w90 oil several days ago, which is the only change since then.

The front driveshaft should not be spinning while the vehicle is in motion unless 4wd is engaged, correct?

Any ideas of what to check first?

[trbankii]

How long have you owned the vehicle? Do you know any of its prior history? Driving in 4WD in conditions that don't allow some slippage between front and rear will bind up the driveline and wear or break components - often u-joints. If a previous owner did this, perhaps it just had gotten to the point where your use of it was the final straw.

[93_Burrito]

trbankii,

He bought the Tahoe from me on 12/29/06. I owned it for about a year, and in that time I honestly only used 4x4 once or twice last winter when we actually had some white stuff. Worked good, too.

I ran a Carfax check on this Tahoe before buying it, and I believe there were maybe 8 owners prior to myself. Other than that anomaly, nothing else showed up in the report. The truck had 95k miles on it when I picked it up in Frederick, MD.

The driver's door has overspray on the inside, someone did some work to it. There were some other dents I had seen before, when the truck was at a dealership in Bethlehem, PA, which were roughly fixed by the time it showed up in Frederick a month or so later.

Other than getting stuck with the bad heads, the truck ran good for me. Don't know what I can do here...


Andy

[trbankii]

With that many owners, hard to say what use it has seen. Very possibly a combination of lack of use of 4WD and possible mis-use of the system and it gave up the ghost. I'd say to replace the u-joint, check to see if there is any binding, and then just go ahead and use it.

My Toyota has manual hubs, so I try to lock them every month or two for a few miles to keep things lubricated. With the Chevy, I take it out in the dirt and shift into 4WD every so often for the same reason.

By the way, welcome to the forums, CoinBall! Have to have a Harrisburg Area get-together one of these days.