I have a bearing noise that I need to chase down and want to see if there is a way to narrow it down w/o chaning a bunch of parts in the process. I know it is hard to describe a noise through the thread on the forum, but hear are the symptons:

Truck has a slight hum / bearing whine that starts at aprox 30-35 mph and progressively gets louder utill about about 65-70 mph (which has been my crusing speed for the majority of my miles...which is alot) The noise is not a high pitch whine, but more like a low grinding moan...like a bad bearing sound. I just don't know which one.

If I bring the truck up to 65-70mph and put the trans in neutral the noise does not go away, but is easier to hear w/o the engine noise.

Is there a way to determine if it a from the t-case, vs one of the carier bearing in the diff? Or maybe a hub bearing?

I just changed the diff and t-case fluid and no burt smell, or shavings found. I am running Royal Purple 85W140 all the way around.

Any thoughts on how to track this down?

 

Wuld seem that if it was not the transfer case, the noise would stop when you let off the gas at 50 - 60.

For hub bearings, any change in sound when going around a freeway curved ramp?

 

Agreed, I kind of ruled them out since the noise i get is while diving in a straight line and does no change when I turn the corners.

I'll have to note what the noise does while crusing and pressing the accelerator (putting the drive train under load) and see what the noise does compared to coasting with no load on the drive train. I have done this, but forgot what I noticed. I'll do it again and post my findings.

 

If you can get access to a lift you can put it in the air, run her up to speed and have someone listen underneath.

 

If it is a high mile truck you should rebuild the drive shafts anyway so could do that and see if it helps. Nothing lost since it needs to be done.

 

Since you’re really at the beginning of diagnosing your problem, might I suggest that you pull the driveshaft’s one by one and take it for a ride. That should help you narrowing down if the noise is coming from a front or rear component. 2001 I “think” you can still crawl under and lock the CDL so that you can drive it without the front shaft.

 

I'll try this and see what happens. The Drive shafts were rebuilt and I've kept them greased so they are in good shape. That was the first thing I looked at, plus I inpect and grease them every 5K miles when I change the oil.

I never locked the CDL before. Is there any trick to this?

 

Removing drive shafts only eliminates them, the wheel bearings (and diff ?)still turn under way, don't they?

 

Removing the drive shaft(s) will remove the torque / lash in the drive line so this will isolate the noise from the front to the back. So this is what I have done thus far and still not sure where the noise is coming from.

1. dropped the front drive shaft to see if there was any noise from the d-shaft / centering ball in the u-joint(s). - No difference in the noise.

2. Jacked up each front wheel independently to check the hub bearing play. Pushing/pulling on the tire at the 12 and 6 o'clock positions revealed no end play. - bearing appear to be in good shape.

3. checked for leaks and no signs of fluid on t-case, diff's pinion or axel seals.

I will try get access to a lift to see if i can get under it with a stethoscope to locate it.


I have a couple of questions.

- Is it ok to drive for a long period of time with the front drive shaft out? I didn't know if running the t-case locked will mess with the TC and ABS systems. Lights on dash are lit up like a Christmas tree.

- Also, I need to pull the bolts off of the flange on the t-case since I had to cut one of the nuts off with a cut-off wheel. The bolt heads do not clear the flange on the t-case, allowing the bolt to be pushed through the holes. Is there a trick to this? What is the easiest way to get these bolts out?

 

I drove my 97 D1 for a week or two while working on the front shaft, but CDL is right there on the console. Not sure if you can pull a lever under yours to activate that.

In regards to a lift, if front shaft is out, and both back wheels are off the ground (jack stands), you should be able to run truck in place. Wheels chocked, nose against something sturdy, etc.