1998 Chevy Astro rumble or vibration when driving

TISMEB4U

MEMBER
1998 CHEVROLET ASTRO
6 CYL
2WD
AUTOMATIC
216,000 MILES

Hello all,

I seem to have acquired a rumble or vibration in our van what seems to be over night. The sound seems to start to be noticeable at about 40 KM/h and continues as you get higher in the speed range.

I have checked the fluid levels and they are all at the right levels including the differential. I can not see any wet spots or leaks from any where on the drive train. The universals in the drive shaft seem tight still (from a manual inspection and turn / shake / pull test. There does not appear to be any leakage at the wheel axe seals.

If I take the vehicle up to speed over 40 KM/h and then put the vehicle into neutral the sound continues and only begins to die out as the vehicle slows below the 35 - 40 KM/h range. Revving the engine to equal RPM's as would be required to get the vehicle to the above speeds does not produce the vibration / rumble. The engine noise through all of it is normal sounding.

If I was to attempt to point to a particular end of the vehicle I would say the sound is coming from the back and travelling up the vehicle to the front. The only other thing I can think of would be the differential, but the fluid is at the correct level and smells normal, the differential is dry at the plate, axe seals, and drive shaft connection so I am not sure why it would be there. It does not have a clunking sound when going into or out of gear, neither does it have it when stopping or starting. I have not tried changing the tires yet although that will be happening soon.

There is no broken leaf springs or leaking shocks so I really do not have any idea what else it could be besides something in the differential yet the rumble sound is the only indicator.

Anyone have any idea's out there? I am handy enough with the van to be able to tackle a lot of things, but I have never really done anything with a differential so this is new ground and I don't want to run it into a shop at the rates now a days unless I am fairly certain it is the differential.

Any thoughts or assistance on this is greatly welcome.

Thanx,
Chad

3 Replies

JACOBANDNICKOLAS

MECHANIC
108,217 POSTS

Have you checked u-joints? ALso, are the rear tires cupped or chopped?

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Wednesday, November 18th, 2009 AT 9:57 AM

TISMEB4U

MEMBER
3 POSTS

I have not taken them apart to inspect them, but I have done the push, pull, twist, shake on them and they seem tight with no excessive play or clicking / clunking sounds.

The tires appear to have even wear on them, I verified the inflation is correct. I can not see and bulges or deformities on the sidewalls or the tread. They are getting close to the wear bar but not quite there yet.