Van Shakes/vibrates

:dupe: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.
:dupe:

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.

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..

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

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

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.

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??

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

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.

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..

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

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:screwy:.
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.

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.

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

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 (:evillol:) 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.)

hey aone, i have a 90 too, mine use to vibrate, i changed one of the idler arms, there are two, it seems they only put two ona few of them, well if you can wiggle it up and down, change them, they are pretty inexpensive and with a pickle fork, and a mini sledge really easy then, also ya check the tires for uneven wear, or perhaps your rotors, i changed one of mine gonna change the right side now, it that doesnt cure the shaking when i put the brakes on then its the tie rods, as for your decerlartion shakes, mine does it, so did a 94 safari i was driving last night, right around 45-50 shakes and shifts when you hit the gas and smoothes out, hope ou dont have the same engine i do, it was suppose to go into a blazers that year, not enough guts, but repplacement parts are a bugger, gotta make sure they are ordering for a 1.5 ton truck not a van, well gotta fix a window switch and heater control vacuum lines, good luck. pm. [email protected]

Thanx Shroom, I replaced the idler arms a couple a years ago. Pretty sure the rotors are fine.. There is no real consistent pattern to when it vibrates and when it doesn't at the point. So something appears to be moving at random. Gears in rear in have play so I am replacing and then we will see.

Just read through the whole thread. Firestone tires? (yikes). The guys at National Tire & Battery were suprised when I rolled up and told them to take what appeared to be perfectly good Firestone's off my truck. They literally went out of round. Truck drove terrible. New set of tires (not Firestone), was like driving a brand new truck. If the gear swap doesn't work, I'd take another look at the tires.

If the rearend doesn't work I would look into the tires again.

I have found that you can usually tell where the problem is by where you feel the vibration. If you feel it more in the steering wheel it is most likely coming from the front, if you feel it more in your butt it is most likely in the back.
I guessing now you hear and feel it more from the back. if the rearend doesn't work.....rotate your tires (back to front, front to back) if the sound and vibration moves....you found your problem.

Kings, Two new firestones on the front. Mixed pair of "sooners" on the rear. Vibration appears to be in the rear. The mixed pair have been on the front for some time and never caused a problem, but could be now. Already too far into rear end to turn around now.

Blazee, Damn I wish I had thought to do that. As I said to Kings above, the vibration appears to originate in the rear. Mixed pair of tires moved back there when I put the Firestones on the front. They caused me no problems when they were on the front. If the rear end replacement doesn't do the job I'll move them to front and see what happens. Hope that's not the problem though after "all" this.:rolleyes: Thanx ya'll..

I know how it goes Aone, I've killed more than one fly with a sledgehammer. Let us know how it turns out.

Hey all, Just wanted to let ya'll know that it appears to be fixed:lol2:. My mechanic friend dropped the rear end in yesterday and drove it some 35 miles and says it was smooth and quiet all the way. Had to make some adjustments to the speedometer but no problems other than that. I will pick it up today and drive it myself but feel confident that the new/used rear end has solved the problem. Also the replacement is posi-traction so I think that is cool:smokin:. Please don't be tellin me about problems with posi-traction now:grinno:, that wouldn't be cool. Thanx to you all for all the suggestions.. I'll be around.

I'm glad to hear you are up and going again.

Drove it last night, with no apparent problems. Do wonder about the speedometer though. Any ideas on how to make sure it is registering the correct speed? I may just need to drive it more to get a better feel for it but seemed like traffic in general was going 60-65 most of the time even in areas where i would have thought 50-55 would have been the more normal "average" speed. Seemed like traffic was pushing on me even when I was doing 65.. Maybe I'm just being :screwy: because I know there is a "chance" the speedometer "may" be off.

If the new rearend is a different ratio it will throw off the speedo, to test it just get somebody you know (perferably someone with a newer car) to drive in front of you at 55, match their speed and see what your speedo says.

Thanx Blazee, I had that thought. Will do.

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 (:evillol:) 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.)



check the Engine and Transmission Mounts

My van was during the same thing. Even after a new engine, it did the same thing. Finally after checking the motor mounts, they found they were bad. After replacment, it did fine. Pray this will help. You have spent a lot of money and time trying to get the fixed.

My vibration feels exactly like a driveshaft vibration. Rotated front and rear tires with no effect.

Vibration is not consistent and appears road surface dependent. Vibration exists in 3rd gear or overdrive. Vibration continues in neutral at speed, so appears to be tire or drive train related.

Had driveshaft balanced twice (second time they did it in front of me) with no effect. Also replaced both u-joints.

Changed tailshaft bushing and seal which resulted in subdued vibration for about 500 miles and then the vibration returned. Had seepage at tailshaft seal and now once again have same seepage.

Measured driveshaft in place with dial indicator and found that rear yoke factory welded with 10 thousandths out of round. Yoke is in round but driveshaft tube is out of round at rear. Apparently welded that way from day one. Would think that balance which hide this defect, so am reluctant to waste money on a new driveshaft.

Rear end yoke has no out of round and transmission tail shaft has no out of round. I will check the pinion nut since that was suggested in this forum. Of course this parts may be out of round at speed due to vibration (chicken or egg).

webrider, you might read GLFarnes post just put up on the board. He spent a lot of heartache and $$$ and found a very subtle source for this problem.

webrider, you might read GLFarnes post just put up on the board. He spent a lot of heartache and $$$ and found a very subtle source for this problem.

Here's the link:

http://www.automotiveforums.com/vbulletin/showthread.php?t=404846

I read the GLFarnes post about the rear leaf springs. I have also considered that the rear axle may be tilting which places the rear u-joint at a severe angle. I will try prying the rear axle yoke to see what pressure it takes to move it, and how far it will move.

Update to my original post, I found a chip out of the harmonic balancer which is on the yoke assembly which slides onto the tranny splined output shaft. The balancer appears to be cast steel, so I mig welded to fill the void (about 1/2 inch long) and ground it smooth. Now I have no vibration until I reach 75MPH. Before I had the problem at 65 and 75. Before and after this fix it runs smooth at 73MPH.

I suspect there is still another anomoly so I will persue the spring issue as described above.