Sometimes when I'm on the highway, doing 70+, and the car downshifts because I'm going up a hill (or because I'm stomping on it), the downshift has a delayed clunk.

 

It goes like this-

lockup converter already disengaged

hill gets steep, car downshifts

tach goes up and stabilizes

1/4 second or so later, "clunk" that feels like its coming from the middle of the car, or slightly to the rear.

 

In fact, it feels and sounds a lot like the clunk when the front spins, and the front-rear clutch goes "50/50", except the downshift clunk is a lot louder.

 

What's oddest is the way the clunk comes after the downshift is finished.

 

I can feel a seat-of-the-pants jolt when it happens, so I'm sure its in the driveline, and not something like the muffler bouncing around.

 

 

Dave

INFO - vehicle? mileage? any prior history...axle, trans, engine work..etc?

 

It only does this at 70+ mph? What if you romp it going slower?

 

How about transmission fluid change, has that ever been done? And replace the filter if it's a 1998+ model. A clunk when down shifting is often bushing related...rear differential or transmission mount. Doesn't seem to be the case here though.

 

Is your AWD and trans working properly otherwise?

Dang, thought I put that stuff in.

 

2003 H6 OBW 63,000 miles, the dealer was *supposed* to do the 60K service pre-purchase, I've had the car since 55K miles.

 

Everything seems to function normally, AWD gets tested regularly in the snow around here, only happens on the 4-3 shift at above 70 or so.

 

 

Dave

It can be as simple as a bad motor mount. It would be really early. Also another thing to look at are the exhaust hangers.

 

Does it do it if you manually downshift the transmission?

 

nipper

that's really new/low mileage for any of the "typical" causes of something like this.

It can be as simple as a bad motor mount. It would be really early. Also another thing to look at are the exhaust hangers.

 

Does it do it if you manually downshift the transmission?

 

nipper

 

Haven't tried a manual downshift yet.

 

What's weird is the clunk seems to come shortly after the downshift, after its already settled in the lower gear.

 

I did try a few times yesterday to get it to happen below 70, and in other gears, and wouldn't clunk.

 

 

Dave

that's really new/low mileage for any of the "typical" causes of something like this.

 

I've been asking myself, is there any way this could be the front/rear torque-split clutch?

 

I can posit a reasonable theory that a downshift at high speed could alter the trans fluid pressure, which could cause a tightening/loosening of the AWD clutch, but since its on dry pavement I can't really spin that into something that'll cause a clink.

 

Dave

I was thinking that, easyiest way to tell, put the FWD fuse in the holder and see if it goes away.

 

 

Are all your tires matching and properly inflated?

 

 

nipper