Van Shakes/vibrates

[Aone]

I have a 90 Astro Van. V6, 4.3, rear wheel drive. I first noticed a vibration when "decelarating" from about 55 mph. It has now begun to vibrate at about 45 mph or >. The severity of vibration is more or less at different times but mostly it vibrates significantly all the time. At times the vibration/shaking is accompanied by a "whump, whump" sound, seemingly from the rear.. Now sometimes the vibration secedes on decelaration. Acceleration alone does not produce the vibration. It seems to be related to speed mostly. The vibration continues even with the engine turned off and it is coasting in neutral. Firestone, replaced a bent rim on front drivers side and repacked bearings on front passenger side. New tires on front as well. I have had the drive shaft removed and "balanced" even though the mechanic stated before-hand that he saw no significant problem there. He further stated the U joints appear to be fine. At his recommendation I took it to a transmision place where the owner drove it but has not yet diagnosed it. He says I need to call for an appointment when he gets caught up on his work. But he did state that he does not think that it is the torque converter. Any suggestions here would be greatly appreciated.

[joey1]

i had a similar problem with a 90 astro.it turned out to be the bug nut on the rear end behind the drive shaft was loose.is the rear end leaking any where? before i tightened the bolt i changed the seal also.problem solved.hope this helps.

[Aone]

Joey1, Thanx for your response. Certainly sounds plausible to me. How do I get to it.. Is this not something that would have been seen or noticed by the guys who pulled and balanced my driveshaft. I am mechanically capable (to some degree), but this is an area that I have never delved into. I've spent most of my time at the front end of the vehicle. I just want to make sure that I'm not working on the heart when this is supposed to be a tonsilectomy (metaphorically speaking). I assume you are referring to the whole housing that the driveshaft runs into as being the rear end. Do I just remove all of those little bolts at the rear of that housing. I really want to fix this myself if I can, first because I enjoy it and secondly because I've put out enough money on the problem with mechanics who haven't helped much. Thanx again..

[Aone]

Joey1,, a mechanic friend has made me a drawing diagram showing me where the pinion/bug not is and how to get to it.. I will let you know if it turns out to be the solution.. Fingers crossed X.. Thanx

[Aone]

Bugnut is firm, Firestone still claims not in tires. I'm at a loss..

[reallytired]

This sound like it could be problem with brakes, tires, or tie rod. If it vibrates at 45-55 miles per hour I would check the tires or tie rods. Make sure the tires don't have a bad spot anywhere and that the tie rods - different parts of the connecting the wheels are not excessively loose. Also may just need an alignment.
If it seems to be vibrating all the time you might want to check your brakes, rotors, & drums.

I have had this problem before and so these are some of the places you might want to check. If you jack it up you can check most of these yourself.

[Aone]

Thanx rt,, I'm still working on it.. will look at items you suggested and let you know..I took it back to Firestone and they swear it's not the tires. It is definetely not in the drive shaft. Not in the motor mounts. After dropping the drive shaft it runs pretty smooth for a few miles then start up again. Mainly on decelaration.. Tis a puzzle??

[balls_to_the_wall]

sounds like the Idler Arm to me. My '94 Safari needs a new one about every 50,000 miles. 248,000 so far.

[rj1721]

I would check the idlers, I got my Astro w/75k on it and the idlers were in pretty bad shape, rom what I hear these vans do seem to go through them, but I would also think any good tire or suspension shop should know that.

[Aone]

I replaced the idlers about 3 years ago, had front end aligned, and have driven the van very little since that time. I use it mainly for utility purposes and to dirve around locally on the weekends. My mechanic friend is now convinced that it is a "pin" that runs down through the center of the rear end. He states that over many miles (mine has 190k on it) these can loosen from their setting from wear and can cause a vibration. He has driven the van several miles as well. I guess I'm going shopping for a used rear end to replace. I feel he is right because of the way the vibration comes and goes arbitrarily something is definitely moving around. I'll let ya'll know.. and thanx much for your responses..

[Kings-x59]

Just a thought, but have you checked the wheels to see if you have lost a wheel balance weight?

[Aone]

Originally Posted by Kings-x59

Just a thought, but have you checked the wheels to see if you have lost a wheel balance weight?

I am assuming Firestone would have done that and yes I know about assuming. However, the vibration is not consistent like a tire out of balance. I drove it about 50 miles to my mechanic friends house this past Saturday. It began to vibrate at 50 to 55 for about 4-5 miles then suddenly smoothed out and stayed that way even decelerating into a McDonalds to get a biscuit. When I came out of McDonalds it began to vibrate again when I got up to speed for about 4-5 miles then smoothed out again and stayed that way until I got to my friends house some 10-15+ miles.
We pulled cover off of differential (the fluid was surprisingly clean/clear for a vehicle with 189k on it) and he feels their is enough play in gears and pin to cause this problem. I am going to buy a used rear end and drop it in and see what happens. I will let ya'll know.

[Kings-x59]

I have a jeep cherokee that vibrates almost exactly as you describe. In my case though I know specifically the problem, which is an out of balance drive shaft. The rear yoke broke a while back the the shaft slammed into the concrete. The impact dislodged one of the balance weights. After the yoke was fixed, the vibration kicks in right at about 50 mph and smooths out some as speed increases. Does it on both acceleration and deceleration under power or in neutral (drive shaft spins regardless).

Anyway, you might check your drive shaft to see if you've lost a balance weight as another possibility.

[Vince64]

Hey Aone
Hope you didn't go out and buy that rear end. I just bought a 96 Astro AWD in Dec and in Jan it started doing the shake rattle and roll on deceleration at around 80km/hr and 60km/hr (sorry dude, I'm Canadian). Lucky for me, I bought the extended warranty. Took it in and they changed the plug wires, cap and fuel filter. Run as smooth as a baby's...... Cost me $400 Canadian.
Good Luck
Vince

[Aone]

Originally Posted by Vince64

Hey Aone
Hope you didn't go out and buy that rear end. I just bought a 96 Astro AWD in Dec and in Jan it started doing the shake rattle and roll on deceleration at around 80km/hr and 60km/hr (sorry dude, I'm Canadian). Lucky for me, I bought the extended warranty. Took it in and they changed the plug wires, cap and fuel filter. Run as smooth as a baby's...... Cost me $400 Canadian.
Good Luck
Vince

Thanx for the reply Vince. Thing is I just did all that not long ago before this problem started. Plugs, wires, rotor button and cap and air filter. Engine runs smooth as a baby's butt. I am sure it is not in the engine. And yes I've got the rear end jacked up ready for a replacement. Getting it out of a 93 at that. I am almost 99% sure that this will fix the problem. If not then I've got a spook () back there somewhere and if I ever find him I'll just have to shoot him. I will let ya'll (that is you all) know the result. XX (crossed fingers.)