Frame and Body Expert Advise Please - CorvetteForum - Chevrolet Corvette Forum Discussion


C3 Tech/Performance
V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

Frame and Body Expert Advise Please

Reply
 
 
 
Thread Tools Search this Thread
Old 09-09-2017, 12:22 PM   #1
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default Frame and Body Expert Advise Please

I have a 79 Vette. I've been rebuilding the front with new ball joints, tie rod ends, shocks and springs. In the process, I noticed the cross shaft on the passenger lower control arm was bent. My assumption is it took a hit. Rather than replace just the cross shaft I replaced the entire control arm. Everything lined up as expected. I then noticed the tire on the driver's side is tucked in the fender about 3/4" to 1" further than the passenger side. I checked the back spacing on the wheels and they are the same. I measured from the shock stud to the fender lip (this should be a fixed location and the same on both sides) which is where I obtained the above measurements. I've read of discrepancies from car to car but this seems a little much. Thoughts would be appreciated.

Thanks in advance,

Brian
DIY-79 is offline   Reply With Quote
Old 09-09-2017, 12:34 PM   #2
Alan 71
CF Senior Member
 
Alan 71's Avatar
 
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 28,599
Thanks: 0
Thanked 2,166 Times in 1,922 Posts
Default

Hi Brian,
No expert here, but a thought.
Have you taken a close look at the area of the frame that the lower control arm bolts to for any signs of damage, ripples, or tears, in the crossmember?

It IS possible that the dimensional difference is caused by the position of the body on the frame, but since your have suspension damage that's the first place to take a look at for clues.
Regards,
Alan

Look carefully at the crossmember in this area.



Last edited by Alan 71; 09-09-2017 at 01:15 PM.
Alan 71 is offline   Reply With Quote
Old 09-09-2017, 12:42 PM   #3
MelWff
CF Senior Member
 
MelWff's Avatar
 
Member Since: May 2006
Location: Danbury CT
Posts: 8,830
Thanked 374 Times in 367 Posts
Default

is there a major difference in the number of alignment shims on the upper control arms between the two sides of the car?
MelWff is offline   Reply With Quote
Old 09-09-2017, 12:58 PM   #4
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

I do not see any damage at the frame where the cross shaft attaches. I did notice the crosss shafts were different from each other from one side to the other which suggests a replaced cross shaft or control arm. Tne shims were set almost identical. 3 to 4 in the rear and one in the front. Also, the brackets holding the vacuum tank and front bumper brackets look fine. No sign of damage. I also measured from the frame to the fender lip on the rear and both sides are right at 12". I was thinking maybe the entire body was crooked on the frame. I have body mounts that I'll be replacing next and I was thinking maybe I have bent bolts. After looking where the mounts are I'm discouraged that that could be it. I didn't realize there were not any mounts past the firewall. Thanks for the replies. Y'all are quick.
DIY-79 is offline   Reply With Quote
Old 09-09-2017, 01:07 PM   #5
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

In retrospect, if you think of the body being like a hand on a clock, if the rear of the body is set correctly and the front is off as you go forward, it will be more exaggerated as you get to the front of the car. Is my thinking correct? Like 12 o'clock to 12:01 or 12:02.
DIY-79 is offline   Reply With Quote
Old 09-09-2017, 01:21 PM   #6
Alan 71
CF Senior Member
 
Alan 71's Avatar
 
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 28,599
Thanks: 0
Thanked 2,166 Times in 1,922 Posts
Default

Hi Brian
There are a total of 8 body mounts.
Just 2 are visible forward of the firewall.
The next pair are at the base of the hinge pillars… hidden but accessible by removing the interior kick panels.
Then there are 2 more at the base of the lock pillars…. hidden but accessible through the small removable panel in the forward area of the rear wheels.
The last 2 are to the rear of the rear wheels…. visible and accessible from the rear wheel wells.
Just removing the 8 bolts won't allow you to move the body on the frame. There is quite a list of other things that need to be loosened or removed in order for the body to shift position.
Regards,
Alan

#1 and # 2 left side


#3 and #4 left side

Last edited by Alan 71; 09-09-2017 at 01:35 PM.
Alan 71 is offline   Reply With Quote
Old 09-09-2017, 01:57 PM   #7
TimAT
CF Senior Member
 
TimAT's Avatar
 
Member Since: Oct 2006
Location: Gladstone MO
Posts: 6,102
Thanked 165 Times in 163 Posts
Default

I don't have a frame dimension drawing for 79, there should be one in the service manual. Try this:

https://www.google.com/search?q=1979...=1504976375014
TimAT is offline   Reply With Quote
Old 09-09-2017, 07:13 PM   #8
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

Got it Allen thank you. Let's say I start with the specs in the link and check my frame measurements. Fix any anomalies, then what's involved in being able to shift the body when all the mounts are loose? I foresee the hood and headlights needing to be realigned. I see a ton of metal from the radiator forward and would love to remove as much as possible for weight loss but I'm thinking it may also function to hold the front clip and fenders in place. How big a bag of worms am I getting into wanting to shift the body 1/3 to a 1/2"?
DIY-79 is offline   Reply With Quote
Old 09-10-2017, 10:01 AM   #9
Alan 71
CF Senior Member
 
Alan 71's Avatar
 
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 28,599
Thanks: 0
Thanked 2,166 Times in 1,922 Posts
Default

Hi Brian,
Some folks feel that getting the body ready to lift for things like body mount repairs or replacement isn't too big a deal, but I think it's a LOT of work.
Plus, once EVERYTHING is loose you'll still be moving something that weighs more than a thousand pounds.
I'd do a LOT of measurement verification before I started down the list of things that need to be done to move the position of the body on the frame.
Regards,
Alan

Last edited by Alan 71; 09-10-2017 at 10:05 AM.
Alan 71 is offline   Reply With Quote
Old 09-10-2017, 10:30 AM   #10
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

Thanks again Allen. I did some reading and apparently there are alignment holes under the door sills. One on each side that a steel rod can be slid through aligning the entire body to the frame. It was suggested in another thread for a guy with a similar issue as mine to check there as well as taking frame measurements. Could be the entire front end was replaced and they just eyeballed the install. Fixing it would require breaking the bonds and reposition the front. If that's the case I'll deal with that when the car is repainted. For now I'm going to continue making the car mechanically sound. I'll post the results of frame measurements and the allignment holes for future reference for those with this problem.
DIY-79 is offline   Reply With Quote
Old 09-10-2017, 12:46 PM   #11
Alan 71
CF Senior Member
 
Alan 71's Avatar
 
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 28,599
Thanks: 0
Thanked 2,166 Times in 1,922 Posts
Default

Hi Brian,
Here are the 2 left side body alignment locations.
The holes have plastic push-in plugs in them.
Checking there will pretty quickly tell you if that part of the body is not square on the frame
Regards,
Alan



Alan 71 is offline   Reply With Quote
Old 09-10-2017, 10:10 PM   #12
Black04Vert
CF Senior Member
 
Member Since: May 2004
Location: Dallas TX
Posts: 916
Thanked 3 Times in 3 Posts
Default

Quote:
Originally Posted by Alan 71 View Post
Hi Brian,
Here are the 2 left side body alignment locations.
The holes have plastic push-in plugs in them.
Checking there will pretty quickly tell you if that part of the body is not square on the frame
Regards,
Alan
What should you see behind the plugs to know that the body is aligned?
Black04Vert is offline   Reply With Quote
Old 09-11-2017, 03:03 PM   #13
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

From what I read, there will be a hole in the frame under each plug. The hole in the body and the frame are the same size. When aligning the body on the frame you slide metal or wood dowels through the holes to hold the body in allignment while you tighten the body mounts up. If the holes are not aligned then your body is on the frame crooked. Like I mentioned above, the rear of the care can be off very little, but as you travel forward it will become more pronounced. Just like a hand on a clock. So say my #4 body mounts are off by 1/16". This will be hardly noticeable with a tape measure from the frame to the fender lip on the rear. But as the body goes forward, the #3's are off by an 1/8", then the #2's by a 1/4" and so on until the measurements at the front fender lip to shock stud are off by 3/4" to and 1". It's plausible and worth checking if you have my issue.
DIY-79 is offline   Reply With Quote
Old 09-11-2017, 03:17 PM   #14
Alan 71
CF Senior Member
 
Alan 71's Avatar
 
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 28,599
Thanks: 0
Thanked 2,166 Times in 1,922 Posts
Default

Hi BO4,
In this photo you can see the front hole on the left side and the rear hole on the right.

If you put a dowel down the the holes in the rocker channels they will be vertical if the body is proper placed on the frame.

Regards,
Alan

Alan 71 is offline   Reply With Quote
Old 09-11-2017, 06:03 PM   #15
Kacyc3
CF Senior Member
 
Kacyc3's Avatar
 
Member Since: Jun 2012
Posts: 1,194
Thanked 45 Times in 40 Posts
Default

Quote:
Originally Posted by DIY-79 View Post
I have a 79 Vette. I've been rebuilding the front with new ball joints, tie rod ends, shocks and springs. In the process, I noticed the cross shaft on the passenger lower control arm was bent. My assumption is it took a hit. Rather than replace just the cross shaft I replaced the entire control arm. Everything lined up as expected. I then noticed the tire on the driver's side is tucked in the fender about 3/4" to 1" further than the passenger side. I checked the back spacing on the wheels and they are the same. I measured from the shock stud to the fender lip (this should be a fixed location and the same on both sides) which is where I obtained the above measurements. I've read of discrepancies from car to car but this seems a little much. Thoughts would be appreciated.

Thanks in advance,

Brian
can you snap some pics, I believe we have the same issue. I have an appointment tomorrow to put my car on a frame rack to check it out.

I put mine on an alignment rack to try and fix it only to get readings of -1.4 Camber DS with no shims and -.5 Camber PS

Quote:
Hi Brian,
No expert here, but a thought.
Have you taken a close look at the area of the frame that the lower control arm bolts to for any signs of damage, ripples, or tears, in the crossmember?

It IS possible that the dimensional difference is caused by the position of the body on the frame, but since your have suspension damage that's the first place to take a look at for clues.
Regards,
Alan

Look carefully at the cross member in this area.
I didnt even think about this, is this possible to fix without a new frame?
Kacyc3 is offline   Reply With Quote
Old 09-11-2017, 06:41 PM   #16
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

I'll snap some pics tomorrow. I'm a fire fighter and on shift. I measured from the Shock stud to the fender lip and have a 3/4" to 1" difference from side to side. So the front clip needs to move to the drivers side the difference. That's not much but dam it's obvious now that I know it. The rear is equal. It's plausible the body is on crooked. It's also plausible the frame is bent. It's also plausible the entire front clip was replaced and they were focused on getting door seams correct and never thought to measure the fender spacing. It could be any combo of the three. Your a step ahead of me by taking yours to a frame shop. I'll be working on her tomorrow. My focus will be ride height and steering linkage followed by a garage allignment. That's all that's left to get her back on the road.
DIY-79 is offline   Reply With Quote
Old 09-11-2017, 07:28 PM   #17
Alan 71
CF Senior Member
 
Alan 71's Avatar
 
Member Since: Sep 2006
Location: Westminster Maryland
Posts: 28,599
Thanks: 0
Thanked 2,166 Times in 1,922 Posts
Default

Hi D79,
The measurement from the shock stud MAY not give you an accurate measurement.
Because the stud is floating between 2 rubber bushings the placement and condition of the bushings COULD affect the dimension.
Regards,
Alan

Here are the front/upper bushings… the larger installs above the frame and the smaller below. You can see how exact location of the stud could vary from side to side. Their design are somewhat 'self-centering' but also allows for a variance.




Last edited by Alan 71; 09-11-2017 at 07:31 PM.
Alan 71 is offline   Reply With Quote
Old 09-11-2017, 07:44 PM   #18
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

Your right. The bushings are new so their condition is not in question but one could be off center high and the other low. I'll find another fixed location to measure from. Tomorrow will be interesting to say the least.
DIY-79 is offline   Reply With Quote
Old 09-11-2017, 07:59 PM   #19
DUB
CF Senior Member
 
Member Since: Apr 2009
Location: Charlotte NC
Posts: 15,272
Thanked 1,400 Times in 1,242 Posts
Default

IF your lower control arm shaft was bent...and you replaced it with a good one...and now the tire is set back to the rear of the wheel well opening.

I would measure the lower ball joint location on that side and make sure that it is not pushed back to the rear of the car.

I also check the wheel base.

You would be amazed that knowing that this car has had something happen to it to cause the lower a-arm shaft to get bent...that it also tweaked the cradle are...and it can be so slight that your naked eye will not be able to pick up on any buckles in the frame metal.

The reason why I know this is because I have repaired this problem many times in the past and pulled it back correctly on the frame machine.

You can check the indexing points under your door sills....but ...if your rear wheels are centered in the quarter panel wheel well openings...that is not the problem.

DUB
DUB is offline   Reply With Quote
Old 09-11-2017, 08:24 PM   #20
DIY-79
Junior Member
Thread Starter
 
DIY-79's Avatar
 
Member Since: Aug 2017
Location: New Braunfels Texas
Posts: 28
Thanks: 0
Thanked 1 Time in 1 Post
Default

Thanks DUB. I'm going to be a measuring fool tomorrow. They're are so many variables. I'm actually thinking the drivers side took the hit and that's why the drivers side wheel is tucked in further. They replaced the lower, which also was the only control arm with an aftermarket ball joint, and left the passenger side thinking it was ok. I've replaced all the ball joints, tie rod ends and the idler arm as well as the bushings in all the control arms. I'll set camber tomorrow. I did a quick camber adjustment to get an idea of where I was at shim wise. Both sides are set in the -1° range but I didn't nail it down perfectly. I also made the mistake of tightening the cross shaft bushing bolts while it was off the ground. I have quite a few things to check tomorrow including making sure the springs are seated properly in the upper spring seat.
DIY-79 is offline   Reply With Quote
Go Back   CorvetteForum - Chevrolet Corvette Forum Discussion >
Reload this Page
  • Frame and Body Expert Advise Please
  •  
     
    Reply

    Related Topics
    Thread Thread Starter Forum Replies Last Post
    Recommendations for a frame shop close to Dallas? Black04Vert C3 Tech/Performance 0 10-16-2017 04:20 PM
    Left Tire is rubbing on fender swag C3 Tech/Performance 12 09-27-2017 10:56 AM
    Front End pre-rebuild observations Reaper19 C3 Tech/Performance 3 07-17-2017 05:54 PM
    manual steering adjustment/control after steering box replacement wolflt1 C3 Tech/Performance 15 05-30-2016 09:42 PM
    Rear not sitting level DanS711 C4 Tech/Performance 21 03-12-2016 02:46 PM


    Thread Tools Search this Thread
    Search this Thread:

    Click for Advanced Search

    Posting Rules
    You may not post new threads
    You may not post replies
    You may not post attachments
    You may not edit your posts

    BB code is On
    Smilies are On
    [IMG] code is On
    HTML code is Off
    Trackbacks are Off
    Pingbacks are Off
    Refbacks are Off

    Forum Jump

    Sponsored Ads
    Vendor Directory

    All times are GMT -4. The time now is 12:08 PM.


    We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
     
    • Ask a Question
      Get answers from community experts
    Question Title:
    Description:
    Your question will be posted in: