Tosten

I have a puzzling humming vibration coming from the front of my Astro. It is a 1997 awe with 117,000 miles and has had this sound since I got it with 96,000 with no change. It starts at about 60 mph and gets worse with increased speed. If I remove the front driveshaft it completely goes away on the hoist and going down the road it is still a bit noticable but not nearly as bad. I've changed the half shafts, tried different tires, changed wheel bearings, tried an aftermarket front shaft. No change. If I take it up to 70 and put it into neutral, it will sound the same until it slows to 60, then goes away. It is a high frequency vibration like that of a universal joint going out. It also sounds like a 4wd left in 4wd on hard pavement. The kicker is that it still does it with all four wheels up in the air. Is there any way to check the transfer case to see if it is locked? I can't turn the front shaft at all when the back wheels are on the gound and the front is up. I'm getting desparate.
thanks

ihatemybike

If it is still there with the front drive shaft removed, I wouldn't be looking at the transfer case. How's the front diff? The front axle seals are usually only good for about 100k and a low fluid or damaged ring and pinion can produce a humming and vibrating.

Tosten

I did rebuild the front differential, I forgot to mention that. The only bearings that I didn't replace were the outer ones where the half shafts slip into. The differential was a bit low when I got the van. Any chance those outer bearings could cause that kind of noise for that long without going out completely? Any chance they could cause that kind of noise at all?
It is a low rumble that is very difficult to trace down, even with a stethoscope.

ihatemybike

Sounds like that's the only thing that's left. They're cheap and fairly easy to replace.

djoker04

Hey Aaron, I'm getting the same thing. mine is RWD..How do I know if the halfshafts need to be replaced....? or the wheel bearings??

ihatemybike

It's rare for RWD axle shafts to go bad, usually need an accident for that. I've had a van with over 200K miles that still had good wheel bearing. Heck, I think Grumpy's are still stock.

When was the last time the rear diff and brakes been serviced?

djoker04

Just got back from Alabama and that noise is definately coming from the front!! My friend who has an Astro said to check the bearings so I will do that this weekend!! The funny thing abut my van on the trip was the on board computer telling my Fuel to Empty...it was sooo off it was funny!! When I got to AL it said I had 80 more miles...but the needle was on the e close to the red line...when I started it up the next morning to get Gas...it went to 40....drove for about 5 miles...LOW....LOL....but she deid me justice....I had the rear Diff checked and serviced when I 1st got it!!

ihatemybike

I believe the Fuel to Empty is based on the current trip's mpg. That would make the number higher after interstate runs, then lower for a in town trip.

djoker04

Well i went 2 miles once I left the HWY to my destination......but yeah that makes since!!

lawheelsdirect

I have an 2001 astro and there was a tsb out about the hudraulic fluid used in the transfer case casuing the vibration. The dealership changed my fluid and the vibration went away.