Simple diagnosis of odd driveline noise - a Tip!

[Manhattan]

For the past couple days (okay weeks) Bushwood has occassionally (okay most of the time) been making a strange squeak/grating sound from somewhere under the Jeep.

Here's what I could tell:
1. The noise increases frequency (timing not pitch) as speed picks up - so must be drive line (not exhaust, vibration, etc.)
2. The noise goes away when not under any load - so it's got to be in the drivetrain; not a hub, brakes, speedo' cable etc.
3. Can not pinpoint even which end of the Jeep it's coming from - seeming like a drivetrain thing???

So, I visually inspect and "shake" all the u-joints/driveshafts - nothing (but a dirty hand)

Okay - the easy diagnostic tip...

I soaked the rear joint on the rear shaft with WD-40, got in, drove it - noise still there. Next, I soaked the front joint on the rear shaft, drove it - noise is gone! So, I've got a u-joint that's on it's last leg. (okay you may have figured that out already but work this was a noise I had never heard before)

Hardly an advanced tip but I impressed myself ;)
by the way - if you do this, don't let the quite u-joint fool you into thinking the problem's solved... it's more like pulling the battery on the smoke alarm and going back to bed...

[Stuka]

You may want to try re-greasing it. They will make more noise if the grease is all used up.

[Manhattan]

I think I'm going to replace both joints on the rear shaft. If it's in good shape, just dry, I'll keep it as a spare.

On the subject - Do you know the best joint I can put in there (stock '88 with D44)? Will a 297 work?

Thanks.