A-body frame damage

A-body frame damage - 07/21/13 07:32 PM

Guess I've struck gold on mine...

Today I was looking for the source of a (suspension) noise when turning to the right while slightly braking. Under the left front of the car a loud 'knack' can be heard everytime.
While removing the left front spindle from the lower balljoint, I remembered a topic here about A-body frame damage caused by metal fatigue.
I examined the frame rails on my car and yes, I found a serious crack running from the bottom of the rearleft K-member mount to the side and up to the bumpstop bracket. Haven't checked the pass.side yet.

I also think I found 'evidence' that the inner fender, and/or shock brace is are flexing enough so they contact each other sometimes.
I'm thinking of welding an angled bracket to both of them and make this area much more resistant to flex.
What dooes one think about all this?

Posted By: autoxcuda

Re: A-body frame damage - 07/21/13 07:46 PM

Had the same stuff with mine in 1997.

Take the k-member off and weld the cracks and plate where possible.

Posted By: jcc

Re: A-body frame damage - 07/22/13 12:33 AM

1. I don't see evidence of shock support flexing, if we are talking about the sliver of rust on the inner fenderwell.
2. I would like to know what other side looks like in comparison.
3. I would like to try and figure out where metal crack started first, that's hard to tell from picture, and the it will be easier to decide what initiated the crack, weld stress, fatigue, impact stress, etc.
4. How long has car had the sway bar, and what size is it?
5. If we consider primarily road bump forces of this area of the frame, there is not a lot of force transmitted to this location, it goes from spindle to lca to tb to the k frame rear bolt mount, however it only one front wheel moves up or down, sway bar then would load this area in front of rear k bolt mount.
5. Dead weight on front end in front of the crack would first cause buckling, not cracking, if we believe cracking is from repeated tension loads.
6. There are numerous other possible loads/combinations, but IMO they are much reduced and less frequent, but possible.
7. I would be concerned just welding up or adding gussets would just move the stress elsewhere, without a good understanding.
8. I would also be curious if others have seen this area cracked before.

Posted By: autoxcuda

Re: A-body frame damage - 07/22/13 01:04 AM

Quote:

...
8. I would also be curious if others have seen this area cracked before.

I just posted detailed pictures of craking in same area around rear K-member bolt in the post above yours.

I have seen cracking in the front under the front UCA bushing in my 68 Dart convertible that has stock t-bars and stock front sway bar.

I have observed some A-bodies in the junkyard with cracking like this when I first experienced it in 1997. Not all, not a majority, just some.

Posted By: BigBlockMopar

Re: A-body frame damage - 07/22/13 10:31 AM

Quote:

1. ... 8. <img src="/ubbthreads/images/graemlins/Twocents.gif" alt="" />

The 'evidence' of the shock support flexing (or inner fender flexing) is a seperate thing I noticed yesterday and pertain to the marks on the inner fender where the undercoating is slightly worn off.
I just wondered if is telling me something should be beefed up. I think it does.

The shocks are the stiffer KYB Gas-filled ones.

The swaybar was added a little over a year ago. It's a Hellwig 1-1/8".
But looking at the installation pic I can already spot some 'anomalies' <img src="/ubbthreads/images/graemlins/smile.gif" alt="" /> at that frame location in the picture...

Here's my view on it;
Personally I think the 'rear' K-member mounting points are acting like a pivot point for frame-flex, causing cracking in that area.
Main reason would be, IMO, the frame there is designed too weak, or the K-member mountpoints should have been reinforced better.
On the front of the K-member, there is the constant 'bouncing-weight' of the engine/radiator and part of the front clip. On the rear of the K-member, there's mostly the 'softer-acting' suspension movements and torsionbar tension.
Then there's the shock supports, giving constant oscillating 'jabs' while driving at the frame rails.

This car was airco-equipped by the way, which would have added more weight on the engine.

Also, all the suspension bushings are poly-urethane since it's last rebuild 2-3 years ago. That won't help softening things either ofcourse.

Posted By: jcc

Re: A-body frame damage - 07/22/13 03:00 PM

Quote:

Quote:

1. ... 8.

The 'evidence' of the shock support flexing (or inner fender flexing) is a seperate thing I noticed yesterday and pertain to the marks on the inner fender where the undercoating is slightly worn off.
I just wondered if is telling me something should be beefed up. I think it does.

The shocks are the stiffer KYB Gas-filled ones.

The swaybar was added a little over a year ago. It's a Hellwig 1-1/8".
But looking at the installation pic I can already spot some 'anomalies' at that frame location in the picture...

Here's my view on it;
Personally I think the 'rear' K-member mounting points are acting like a pivot point for frame-flex, causing cracking in that area.
Main reason would be, IMO, the frame there is designed too weak, or the K-member mountpoints should have been reinforced better.
On the front of the K-member, there is the constant 'bouncing-weight' of the engine/radiator and part of the front clip. On the rear of the K-member, there's mostly the 'softer-acting' suspension movements and torsionbar tension.
Then there's the shock supports, giving constant oscillating 'jabs' while driving at the frame rails.

This car was airco-equipped by the way, which would have added more weight on the engine.

Also, all the suspension bushings are poly-urethane since it's last rebuild 2-3 years ago. That won't help softening things either of course.

Regarding the "bouncing" weight, how much in front of the rear k mounting bolts are the motor mounts? Doesn't seem bumper, grill, radiator, etc would be enough to initiate this cracking, but if motor is much front, then I would think we would see some evidence of buckling, and I don't disagree something is weak, and we have evidence of 2 cases, just want to make sure we put tail on the right end of the horse. And if it is cracking, it is also very likely entire area is flexing more then acceptable from a handling perspective.

Still can't make out the shock tower issue, but it might be related, and the KYB shocks OT,

Posted By: BigBlockMopar

Re: A-body frame damage - 07/22/13 03:35 PM

Agree the frame is ofcourse not 'weak' enough to buckle, but I believe it is still weak enough to allow (excessive) flex, which in turn would cause cracking.
I would really like to mount a camera somewhere in the wheelwell or engine bay and see if... No, how much flex there is actually going on in the front end while driving around during various situations.

As for the KYB's... I've never driven in an A-body with 'better' shocks so I really wouldn't know yet why these are considered 'bad'. Sure I've read about it, but I'm more a 'find out myself'-kinda guy...

Posted By: Kern Dog

Re: A-body frame damage - 07/23/13 07:50 AM

Quote:

As for the KYB's... I've never driven in an A-body with 'better' shocks so I really wouldn't know yet why these are considered 'bad'. Sure I've read about it, but I'm more a 'find out myself'-kinda guy...

I have run the same set of KYBs for 12 years. I have wondered why so many people have harsh opinions on them. thats why I started THIS thread:

https://board.moparts.org/ubbthreads/show...amp;Search=true

Posted By: BigBlockMopar

Re: A-body frame damage - 08/29/13 09:32 PM

Small update; I found a similar crack in the pass.side framerail of the car.
It hasn't migrated to the side of the frame yet but at the bottom it is fairly noticable.
Couldn't take pics at the moment because of a pair of filthy hands.

I was able to tighten all the K-member bolts about half a turn though.

Posted By: PHJ426

Re: A-body frame damage - 08/30/13 01:10 AM

Anyone ever use the frame caps from Auto Rust Technicians here:

http://www.autorust.com/2008cat.pdf

Posted By: jcc

Re: A-body frame damage - 08/30/13 02:13 AM

Quote:

I was able to tighten all the K-member bolts about half a turn though.

Do you know if they were tight previously, ie have they loosen, or is something giving way?

Posted By: BigBlockMopar

Re: A-body frame damage - 08/30/13 08:11 AM

The PO has had the entire front end apart for powdercoating at one time. He did mention when he sold the car to me to be sure to check all the fasteners under there as he knew not all of them where fastened properly yet.
Over time I've learned he was [email]d@mn[/email] right about that! <img src="/ubbthreads/images/graemlins/rant.gif" alt="" />

Instead of leaving untorqued bolts actually visably loose, he had just tightened everything 'just snug' and parked it outside for later worry.

Posted By: BigBlockMopar

Re: A-body frame damage - 03/23/14 01:57 AM

Topic-update;

Today I found some time to tackle the frame-damage on the Dart. Just did the driver-side for now, as this side had the worst damage.

Started out by cleaning everything down to bare metal as best as possible, with the K-member still in place.
I dimpled the damaged areas of the frame a bit, layed down some welds are ground them down again. The metal of the frame felt really weak in the damaged areas.

Then I slit a piece of angled iron between the loosened rear K-member mount and frame, and welded that to the frame as much as I could.

Not pretty but I felt it was fairly effective.
I also welded a piece of angle iron between the shocktower and the inner fender. Will weld another piece tomorrow and maybe repair the pass.side frame aswell.

Posted By: joes68340s

Re: A-body frame damage - 03/30/14 09:15 PM

This is interesting damage as I have some severe tears in the same location On a 70 Cuda. I wonder how much is fatigue and corosion.

Posted By: Kern Dog

Re: A-body frame damage - 03/30/14 10:14 PM

You must "street drive" that car a bunch. Look at the condition of the sway bar and bushings between the first few photos and the recent ones!
I respect a street driven car, wear and tear and all !

Posted By: BigBlockMopar

Re: A-body frame damage - 03/30/14 10:32 PM

It's my daily driver in summer and winter.
But the roadsalt from the 2012/2013 winter was what did the most visible 'wear'.
This year we didn't have a winter here so no salt ended on the roads fortunatly.

Posted By: BigBlockMopar

Re: A-body frame damage - 05/11/18 10:53 PM

4 years later:
The right side of the car's frame rails are desperately up for repair...

Posted By: 68rrunner

Re: A-body frame damage - 05/12/18 11:44 PM

I've seen this as well. It seemed that the culprit is actually the brace/plate that the factory welded in the rail. These accumulate dirt and moisture and rust/stress crack and then require repair. If you look at the picture above, the spotweld on the bottom of the rail holds that plate in place.

Posted By: NV69B7RR

Re: A-body frame damage - 05/13/18 06:36 AM

BigblockMopar, does your car have any type of chassis stiffeners in the car(Cage, sub frame connectors, etc)?

Posted By: BigBlockMopar

Re: A-body frame damage - 05/13/18 11:05 AM

Just a pair of homemade welded in subframe connectors.

I believe I mentioned it some years ago in some topics, but I can't help but wonder if just simply welding the entire K-member onto the frame rails would be a much better idea, just like C-bodies that have a one-piece front frame).
With use a some proper gusseting near the mountpoints I think the entire front end will be unsurpassed in strength.