Hi folks,

My wife's 2008 Grand Caravan has developed some kind of an issue. About 2 weeks ago or so, a faint sound appeared under acceleration that sounded like a lifter knock, we went on a trip and it never got worse, but it didn't get any better. Today, that little knock developed into a major knock/thud sound when you drive the car.

A little more background. Before we left last week I rotated the tires from back to front. Tightened bolts to 90 lbs and all was good until we were on the road and the steering wheel started vibrating (I'm thinking wheels are out of balance since the back wheels were moved to front, but I never got to check the weights yet). - the noise was present before the wheel rotation.

Here is what I found :

- no knock when idling

- no knock when increasing RPM in P/R/D/N when break is on - makes me think not lifters

- when car is taken for a ride the knock develops around 10 km/h as the van is accelerating and get's louder and faster

- when gas pedal is released (no acceleration) the noise goes away - makes me think not wheels/calipers/etc

I'd like to figure out as much as I can before taking it in to the stealership for diagnostics as I have this uneasy feeling this is transmission related.

Any help is much appreciated !!!

Thanks,

-jeepzj

 

Sounds like a C/V axle. When bad, they can typically make noise under acceleration, but stop when the gas pedal is released.

 

Any way to test it to see if it is the culprit?

 

Most mechanics will diagnose by driving it. It generally has a unique sound and feel.
If you get it up to highway speeds, let off the gas and it's quiet, hit the gas and it thumps, I'd put my money on the axle.
Question is, which side? Do you have any sensation from the floor boards as to drivers side or passengers side? Check for any broken axle boots or grease slinging around the axle area.

 

rjamreed,

I agree, sometimes it takes feeling it in a test drive to really know what is wrong. I'd also put my money on the axle based on the symptoms described as well.

@jeepzj - The only other thing I could suggest would be a wheel bearing. Similar noise when accelerating and it becomes more noticeable the faster the vehicle is going. May not be the case but a possibility.
Keep us posted after heading to the garage if you can.

 

You can often get a wheel bearing to change sound by a little bit of swerving. ie. you swerve left, it makes a noise, swerve right, noise goes away.

Obviously, don't do this at highway speeds or on the interstate.....

 

[QUOTE=jeepzj;3148053

A little more background. Before we left last week I rotated the tires from back to front. Tightened bolts to 90 lbs and all was good until we were on the road and the steering wheel started vibrating (I'm thinking wheels are out of balance since the back wheels were moved to front, but I never got to check the weights yet). - the noise was present before the wheel rotation.

Here is what I found :

- no knock when idling

- no knock when increasing RPM in P/R/D/N when break is on - makes me think not lifters

- when car is taken for a ride the knock develops around 10 km/h as the van is accelerating and get's louder and faster

[/QUOTE]

You said you torqued it to 90 lbs, if my memory is correct, specs calls for 100lbs (someone correct me if I'm wrong). Maybe the wheels are loose and causing the knock. Would make sense since no knock when idling or increasing RPM in PRND and it knock gets louder as you drive faster.

 

It feels to me like it's coming from the passenger side of the van. I will take a look under and look for obvious signs of damage. If nothing is visible any easy way to tell if it's buttered up? On my 96 jeep I could tell when my U joints were gone as I could feel how loose they were. Would that work?

 

I'm going to take the wheels off tomorrow anyways to look at the bearings and CV, so I'll check the torque on the wheel bolts as well.

 

You may want to go back over the torque settings on the lug nuts. Now that my wheels have been off many times and subjected to "mechanics" hammering the nuts home with an impact wrench, I find that I have to drive 30-40 miles and then retighten. My understanding is that the threads stretch if overtorqued which then requires later retightening.