The LCA front mounts are known for sometimes not being exactly right, it was dependent upon how much the guy drilling the holes had to drink that day LOL.

This may cause what you are seeing, not sure on the frame spec's I can do some digging through the stuff that I have and see what I can come up with for you.

I do know that there was a TSB, or I thought rather, about opening the LCA mount holes to accommodate for the hole variance. I will dig and see what I can find for you.

 

Wow, my brain is fried. I just found the older thread I had on this issue where you mentioned that and Lance posted the bulletin/fix. Thanks for the reminder, I guess I never caught it in my old thread. I am going to check that but even if that is the case, it's still a strange coincidence that my measurements from diagonal reference points from the frame near the LCA pockets to the rear xmember are off by 3/8ths of an inch. I didn't think acceptable tolerances in the 90's would be that bad but then again, with the things that happened with these cars (LCA holes being off) I don't know if i'd doubt the acceptable tolerance being a half inch anymore LOL

I want to do a few measurements to check to see if the rear wheels are parallel with the front...just have to get the front suspension together. I am thinking that will tell me with the most accuracy if my diff is square with the front...or if it's off, if it's a matter of it being angled to one side front to back or if it really is in the car square but shifted to one side. hmmm

The measurements I took after posting my last thread told me that the rear wheels were parallel with the rear frame rails. IF the rear was skewed due to bad mounting points of the LCA's, the wheels would be different differences to the frame rail at the front of the wheel vs. the back. Mine wasn't but it's something I definitely want to double check.

 

Yeah I see what you mean, I looked through all of the manuals that I have and I can't find anything that will reference the measurements, with plus or minus. May try pm'ing Bill Harper, he would probably have the information.

 

I do have some info--need e-mail address to send to.

 

Kris396SS@gmail.com. Any info will be much appreciated! Thanks Bill!

Hopefully I can get to the bottom of this once and for all.

We are building a car for a local body shop owner who is a friend of my boss. My boss told me he is going to ask him if I can borrow their frame measuring tram/tools to check it all out. Hes had one of our floor jacks for two years so I don't think it'll be a problem lol.

My plan of attack is to first check the frame itself. If there is something wrong, have the frame straightened. Then put the car on a 4 wheel alignment rack and make sure everything is OK.

It's just too bad I just finished getting my last coat of paint on the frame...hope it doesn't have to go to the frame straightening machine because I am sure it'll get beat up some.

 

I have frame charts at home.
If Bill doesn't come up with them Email me

As for the discrepancies, the factory "goof" was a rear control arm mounting hole

 

Thanks again for the files Bill!

And Gerry, Bill informs me he received these from you a ways back so thank you too!

Hopefully I can get out there tonight after work to take some rough measurements with the tape then hopefully I can get that tram...

One thing that strikes me as odd though is the measurements don't seem to have any square check for the main rails to the rear xmember. The diagonal measurement they seem to want to use to check that is from the main rail to the end of the frame rails....

I thought that to be weird because the rear rails can literally be flexed a good amount just by grabbing them, and it seems like the body/rear bumper jigs them up if anything and that by no means is an accurate way of keeping them inline. I would think any measurement using them would be less than accurate, not to mention that are relatively unimportant even if they were bent. As long as from the rear x member to the front k member were good you'd be ok. hmm

 

Thanks again for the diagrams guys. Did the FSM or book you got those from have any GM recommended margin of error? I am guessing/hoping in the 90's it would be no more than 1/4-3/8ths of an inch?

I did some measuring out in the garage before with the tape (didn't get the tram yet).

From the specified point towards the front of the frame to the one that's right after the LCA pocket (spanning across the whole center of the frame, front to back) I measured 83 9/16 on one side and 84 even on the other. Specs were supposed to be 83 3/4. So I wasn't far from the specs either way, but the tolerance stacks up to 7/16's of a difference between the two. That seems a little on the high side (for a non 60's/70's cars I would think).

Most of the other points were pretty good aside from the rear of the frame, the last measurement from body bushing hole to body bushing hole was a full inch short. I am going to bolt the bumper back on to and take all the back end measurements again though, as the rear rails can be flexed quite a bit by hand and the bumper acts as a jig and spread them out a bit. I just need to see what that does to the rest of the back half measurements as most of them were dead on.


So that is what I found so far. I'll be checking out the rear/mounting locations etc... if I get a chance tomorrow.

 

Thanks again for the diagrams guys. Did the FSM or book you got those from have any GM recommended margin of error? I am guessing/hoping in the 90's it would be no more than 1/4-3/8ths of an inch?

... .

FSM says "Corresponding measurements must be equal to within 6mm (1/4 inch)"

 

I could be talking out my rear but I'll say it anyway. While I understand where you are coming from, unless there is damage, I would not worry about it. When I did my frame swap, I actually swapped frames with a donor car. Not because mine had any problems, it was more for convienence. I knew my car had been hit in the rear quarter at one point in it's life and the new frame came from a car that had never been hit. My biggest worry was after all that work building the new frame, the my old body and the new frame would not match up. Your frame came from your car. If you were to straighten the frame while not attached to the car, you risk "fixing" it so the two are not a matched pair anymore.

 

SSQUATCH, thanks for your reply! I do know what you're saying about that, and being that many parts of a frame could potentially be bent yet NOT throw off wheelbase geometry would mean that fixing it it would simply bring up potential problems with mating the body to the frame.

However my biggest concern is that of the wheelbase. If the rear wasn't so visibly shifted to one side, I probably wouldn't care too much but I am just worried on the implications this could have on the ride of the car and also the (minor) pain in the butt i'd have with fitting the widest tire possible/having to space one side out for cosmetics. My aim isn't to nitpick whether or not the frame is bent, I am really trying to figure out why the rear is so badly shifted (as much as 1/2 inch) to one side of the car...be it because of a bent chassis or possibly due to something else.

All the time and money I put into this car, I definitely want the foundation to be good.

 

I completley agree and understand. When I initially set the body back on the frame, I centered the frame with the body. The rear axle was not even close to being centered from side to side. I had to "cheat" the frame over to one side as far as it would allow to get it to look right. I think I ended up within 1/8 of an inch side to side tire clearance in the wheel wells and thought I was done.... but I wasn't. When I went to bolt the front sections of the car I realized I had to skew the frame a bit more to get it to fit and "look" right. I think I spent 2+ days just trying to adjust it. Thank god our cars are weigh next to nothing or else it would have been difficult

 

Hmm, just curious...did you ever check wheel to frame clearance when doing this? If your frame was centered under the car and the wheels weren't right, perhaps you have the same issue as me (as in this is a manufacturing thing not a result of something being bent). I wouldn't think it's a result of a factory pinion offset because it seems like they would have lined the bumpstops, pinion snubber and spring perches up...but who knows.

 

SSandman - I had the same issues with SS.

Rear axle was shifted to the passenger side and shifted to the front of the car on the passenger side.

No measurements required. It's that obvious to the naked eye.

I am 100% sure my issue is the hole in the frame for the rear lower control arm not being stamped in the correct location on the frame.

Easy fix for all of the issues?

Adjustable rear upper and lower control arms.

 

One of my 94 9c1's was hit hard right above the right tire. The axle survived with no issue, and the car drove straight. I found out when I was putting my 91 body on that the entire kickup area was knocked to the right about 5/8". I ended up junking the frame, and found a killer deal on a L99 9C3 Caprice that had an engine fire. Junkyard sold me the entire rolling frame with a 3.23 LSD in great shape for $400. It was cheaper than straightening the existing frame.

Ya gotta remember that while your car is a 95 or 96, the frame tools (and frame) were designed in the 70's. A lot of the frame is supposedly similar/the same as a mid 70's Monte/Cutlass, so the frame design may even be older than that. Stamping long sections like that and dimensional control were not what they are today.

These days it's not uncommon for frames to have all the suspension pickup points pierced in one operation, i.e. in a jig. That way all of points stay pretty tightly controlled relative to each other.

 

So what was the end result hear and can I get the email with that info 206whips@gmail.com

 

A year after I bought my 94 SS, I took it in for it's first alignment. The service writer asked me if the car had been in an accident. But it had not. I had bought it new. He told me that one wheel was further forward out back than the other, and the alignment would be tough. Same issue at every alignment after that. My thought back then was that one of the lower control arm bolt holes was drilled wrong.

 

Did it drive with any problems or want to track left/right?

 

I found a factory Technical service bulletin in my files.

Rear wheel/tire position in wheel well opening.

Bulletin no; 53-34-03

Dated May, 1995

If you can not find it on line contact me and I'll scan it for you.

 

Granted this thread is very old can the original poster/responders email me any of the information shared in this topic?

I have begun tearing down my 94 SS #3120 as I am in the same "bad frame" boat. Email is twizzard21@yahoo.com