Chevy & GMC Vans

OK guys... I'm so close to going to the local car dealership and buying a new car.....so I'm gonna need some help to talk me off this astro van cliff!

Here's what I've got going on. Last summer was driving towards Seattle on I5 and suddenly a weird vibration started....but only when you would let off the gas (foot back on the accelerator and vibration gone). I let it go for a couple months since I don't drive this van everyday.... But it started to get worse so here's what I've replaced:

•all four tires
•all wheel bearings.
•all four shocks
•motor and tranny mounts
•all four brakes
•all steering components (idler arms drag link pitman arms etc.)
•upper and lower ball joints
•front u joints twice (just to be sure they were installed perfectly) front drive line serviced and balanced by local specialists and then bought replacement newer version for this 98-the one without the wizard sleeve looking thingy on the one end just because)
•rebuilt transfer case
•new front end

All of this and the vibration is now worse than ever....actually seems that it is there all the time at speeds over 40mph and not just when I let off the gas.

Help!

Jamie

Rear u joints twice also

hmm, maybe just fluke but when I bought my van it had the same problems as described at highway speed. ( Mine's an 03 AWD btw ) and I also had a griding / popping noise at low speeds manuvering around parking lots, into parking spaces ect.. I changed the rear brakes and at the same time changed the diff fluid to the GM Spec stuff for AWD ( autotrac 2 IIRC ) and both the noise and 90% of the vibration went away.

I forgot to mention I did change rear diff fluid. No sharp teeth in there and tolerances seems fine. I did use the expensive gm fluid.

By the sounds of it, I would say you need new rear axle pinion bearings. Pull the rear drive shaft off the pinion and see if there is any movement in the pinion. Have the van on jack stands under the rear axle so the tires are off the ground and turn the pinion and feel for noise, roughness etc.

I'm with Lifted... check the rearend. I'm guessing something is amiss. I wouldn't be surprised if it is a ring and pinion issue.

... and check rear springs for sagging. If I remember right; you shall have no more than 1,5 degrees off between trans output and rear axle pinion (ie. each end of driveshaft).

here is a scary thought.
Sometimes the bracket that attaches the leaf spring to the axle, rusts out and tears open.

blacknome wrote:hmm, maybe just fluke but when I bought my van it had the same problems as described at highway speed. ( Mine's an 03 AWD btw ) and I also had a griding / popping noise at low speeds manuvering around parking lots, into parking spaces ect.. I changed the rear brakes and at the same time changed the diff fluid to the GM Spec stuff for AWD ( autotrac 2 IIRC ) and both the noise and 90% of the vibration went away.

re-read my post and mentioned the diff... I meant to say I changed the fluid in the Transfer Case and most of " off pedal at highway speed " vibration went away

Hope you are able to find the problem 'cause you sure did a lot of work. Look forward to hearing how you make out.

I had similar issues on my 97, I dropped the rear d.shaft, and tightened, and re-peened the pinion nut. no more problems. I think its a 36mm socket needed.

dvil wrote:... and check rear springs for sagging. If I remember right; you shall have no more than 1,5 degrees off between trans output and rear axle pinion (ie. each end of driveshaft).

You can be off much more than that if your talking about the height difference but if your speaking of angle difference,,,you'd be about right. In other words,,,if you have a 3* drop on tranny,,you need upward on pinion 3* but there can be much more height between the two.

Could you have possibly slung weights off d/s ?

Thanks for all your input guys...here is the fix and the update....... IT WAS THE DRIVELINES!

After all the parts and money I spent it was the drive lines. I took the van to Dans gears in sherwood oregon to have the rear diff looked at thinking it had to be something inside. He ran the van on his rack and said that both rear and the second generation front driveline were about thirty five to forty five thousanths out of whack. Front and rear both being screwy is why I couldn't pin point the vibration if it was coming from the front or back....it was everywhere!

Long story the van is now running smooth and quiet. I can now sleep at night! Cheers!

Jamie