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Front end clunk FINALLY diagnosed


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As some of you may know, I have been trying to track down the source of a front end clunk for the better part of a year now. Well, the good news is it has finally been diagnosed. The bad news, there's no cure for it (as far as I can see).

I'm not sure how I or anyone else missed this, but I brought it to my brother's shop for an oil change a couple days ago and asked him to have yet another look around for the clunking source while it was on the pit. Somehow, some way, my frame is twisted. The driver side sub frame is shoved backward, and the passenger side shoved forward, thus "twisting" the entire car. The clunking? On the driver side where the control arm connects, is whacking into the ABS unit every time I hit a bump. And on the passenger side, one of the motor mount bolts is hitting the frame where it is bent. Like I said, I don't know how this happened. I guess it's possible it was like that when I got it and I didn't notice. I was told that it might be possible to try to straighten it, but odds are it would do more harm than good. It's pretty lame that I can't repair it, but I feel a little better at least knowing where it is coming from.

I have to go get a new belt put on tomorrow (the 3rd one in 3 months thanks to a faulty tensioner), so while it's over the pit I'll take a picture or two and post them. I just wanted to share my findings.

big4870885.jpg

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A good frame shop *can* fix this. I also doubt that it would be expensive, but I would exepct a bill of a few hundred dollars because the cradle would have to be dropped to provide access to the frame machine anchors.

It was likley caused by a previous collision (not likely because an incomplete fix would have been difficult to sell to an insurance company) or by a really bad hit on the front wheel, like a two-foot-deep pothole about a yard across, at a speed of about 35 mph or so, which would have likely disabled the car and quite possibly have set off the air bags, which are calibrated to go off with impacts great enough to collapse the bumper shock absorbing struts, and probably damaged the LF tire and wheel. Thus you would have, uh, noticed it.

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Most body shops are going to have a frame straightener (that's what they do); the least you should do is get an estimate (then you can make a decision). Apparently you vehicle drives okay, but perhaps have someone drive behind you and see if it tracks down the road straight. I'm sure you've seen improperly repaired cars run down the road askew; not cool. Anyway, as Jim stated, might not cost too much to fix.

Chuck

'17 XT5, '04 Bravada........but still lusting for that '69 Z-28

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subframe is bolted to unibody. if subframe got hit hard enough to make it not square, i would expect subframe bolts to also be bent. you would think the bolts would try and bend just prior to subframe bending. worse case, get another used subframe and hope unibody is not tweaked. probably 1 side is slightly pushed back from hit. when shop does lower case reseal, they drop subframe and hold motor/trans from top. so it can be done. saw a nice 96 sts at yard last fall. motor was gone but subframe was laying on ground next to car. there you go.

Edited by joeb
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"or by a really bad hit on the front wheel, like a two-foot-deep pothole about a yard across, at a speed of about 35 mph or so"

That's about the size of all the potholes in the roads where I drive. :D Maybe that is what is causing my 97 Deville to clunk.

Glad you found your problem Carla. I am sure you can have it fixed, I just hope you can find someone to give you a reasonable price to fix it.

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I agree with Joeb. If the Engine Cradle is bent it can be replaced either new ($465.97) or see if you can pick one up in a junk yard. However, these frames tend to rust, particularly at the rear where bolted to the undercarriage, which causes mounting assemblies to break away from the cradle. There should be two cradle mounting assemblies at the rear of the cradle on both sides.

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I didn't get a chance to get under there and take a pic of it today, but I really want to get one posted on here. Perhaps seeing the damage will make it a little easier to tell if it can be fixed? It looked to me that there was a dent in the front part of the cradle/subframe, but it was oddly perfectly symmetrical, which made me think it was supposed to be slightly concave there. I'll take a better look in the morning and get some pics up. If it can be fixed then I would definitely like to look into it. I love this car and plan on driving it for as long as it will let me. Considering how well it runs, how good the body looks, and that there is only minor surface rust on the underneath..I can't see ever junking it because the frame kicked the bucket. 173,000 miles and still kickin!

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i suppose a trans shop could replace a subframe since they drop them in order to pull trans. my car is pretty nice but i have an urge to replace it. longest i have ever owned 1 car. 10yrs.

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....It looked to me that there was a dent in the front part of the cradle/subframe, but it was oddly perfectly symmetrical, which made me think it was supposed to be slightly concave there.

I'm easily confused but if you are talking about what is commonly called the "cradle", then yes - it can be replaced. With either a new or a "recycled" cradle.

What is universally referred to as the cradle is the approximately square piece which is the mounting point for the engine/transaxle assembly and the bottom end of the front suspension components. The cradle is attached to the unibody with 6(?) or 8(?) bolts through stiff rubber mounts.

If the cradle is damaged (distorted) enough to be visible to the eye, I would expect the car would be very unstable as far as steering line is concerned at highway speeds. Expressed another way, the driver would constantly be using steering wheel pressure to maintain a straight line.

You could (very carefully) measure the front to back on both sides, and side to side at both ends, and most importantly, the diagonal dimensions. The diagonal dimensions MUST be equal; as in exactly the same.

As to the "dent" you mentioned, there is a dimple in the center of the front side to side piece. But I can picture someone in the past using too small a jack under that location to lift both front wheels off the ground at the same time. Not a great idea.

Jim

Drive your car.

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yeah there is a curve in the subframe, front side where the plastic gaurd bolts on

That would be exactly what I am talking about I believe. That's a relief at least to know that "dent" is supposed to be there. The weather is finally decent today, so I am going to go take a few pictures in about an hour or so...

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