Reply
 
Thread Tools Display Modes
  #1  
Old 11-16-2023, 09:18 PM
MDGOAT69's Avatar
MDGOAT69 MDGOAT69 is offline
Senior Member
 
Join Date: Dec 2016
Location: Brockton, Massachusetts
Posts: 154
Default Subframe Crack - 79 TA

Looking for some guidance here. I was doing some cleaning and prepping of my engine bay with the engine out and noticed this crack in my subframe. This is on the crossmember portion under the engine. Does anyone think this is repairable via welding or do I need to bite the bullet and get an entirely different subframe?

Also, does anyone have all of the measurements handy for checking a subframe for squareness?

Any help/guidance is greatly appreciated.
Attached Thumbnails
Click image for larger version

Name:	IMG_2633.jpg
Views:	168
Size:	82.0 KB
ID:	623367   Click image for larger version

Name:	IMG_2634.jpg
Views:	143
Size:	94.4 KB
ID:	623368   Click image for larger version

Name:	IMG_2635.jpg
Views:	143
Size:	77.4 KB
ID:	623369  

__________________
1979 Trans Am: Y84 WS6 400/4spd
1967 YS 400, 670 heads, Summit 2802 cam, long tubes, ST-10 trans. McLeod hydraulic clutch conversion.
  #2  
Old 11-16-2023, 09:41 PM
4dblnkldude's Avatar
4dblnkldude 4dblnkldude is offline
Ultimate Warrior
 
Join Date: Oct 2006
Location: levittown
Posts: 1,873
Default

Wow, I saw the first two pics and thought about "Ving" it out and running a bead in there. Then I saw the third picture. Sorry I do not have measurements.

__________________
" Is wearing a helmet illegal" Mike Kerr 1-29-09
  #3  
Old 11-16-2023, 10:03 PM
694.1 694.1 is offline
Ultimate Warrior
 
Join Date: Jul 2010
Location: SE WI
Posts: 1,372
Default

The frame people at Snap-On/Blackhawk will have measurements.
Great catch, it looks like the metal was a little too brittle.
Should be fixable.

__________________
"At no time did we exceed 175 mph.”
Dan Gurney's truthful response to his and Brock Yate's winning of the first ever Cannonball Baker Sea-to-Shining Sea...

Still have my 1st Firebird
7th Firebird
57 Starchief
  #4  
Old 11-17-2023, 10:11 AM
TAKerry TAKerry is offline
Ultimate Warrior
 
Join Date: Feb 2018
Location: North Eastern MD
Posts: 1,148
Default

Meausurements are in the fisher body manual. I dont have anything on the computer to scan, would have to dig the book out of the shop.

  #5  
Old 11-17-2023, 12:37 PM
Shiny's Avatar
Shiny Shiny is offline
Ultimate Warrior
 
Join Date: Nov 2008
Location: Centennial CO
Posts: 1,910
Default

Quote:
Originally Posted by 694.1 View Post
The frame people at Snap-On/Blackhawk will have measurements.
Great catch, it looks like the metal was a little too brittle.
Should be fixable.
You have a tough decision to make.

I would want to know why it cracked before making a decision to repair or replace, but that's just me.

You seem to be questioning whether the part could have been bad and therefore, not worth repairing, correct? Like 694.1 speculates about the material being brittle...

The jagged, random path of the crack suggests to me it developed slowly over time...probably fatigue and could have been helped by corrosion. Brittle cracks tend to propagate fast and in a straight line like the pink:



But the crack wouldn't be there without this being a high-stress location for the part.

The part is probably stamped from relatively strong cold-rolled steel so welding should be able to repair it. How long it lasts after comes back to understanding why it cracked but, IMO, the crack by itself doesn't say the part was bad to begin with.

You also know replacing the part removes a lot of uncertainty. If you weld it, will you trust it or worry about it?

Good luck.

Mike
Attached Thumbnails
Click image for larger version

Name:	Crack.jpg
Views:	188
Size:	74.0 KB
ID:	623405  

The Following User Says Thank You to Shiny For This Useful Post:
  #6  
Old 11-17-2023, 02:50 PM
Scarebird's Avatar
Scarebird Scarebird is offline
Ultimate Warrior
 
Join Date: Nov 2002
Location: ABQ, USA
Posts: 5,023
Default

I would find another subframe.

  #7  
Old 11-17-2023, 07:35 PM
Trevor78 Trevor78 is offline
Suspended
 
Join Date: May 2022
Posts: 595
Default

It appears you have the original bridge jump Bandit.

I'd replace if it were mine. Can be fixed as is but I'd want mine ground back flush and unseen and paint touched up, easier done when not attached. Perfect time for a nice powdercoated finish to protect before slipping back under.

The Following User Says Thank You to Trevor78 For This Useful Post:
  #8  
Old 11-17-2023, 08:39 PM
MDGOAT69's Avatar
MDGOAT69 MDGOAT69 is offline
Senior Member
 
Join Date: Dec 2016
Location: Brockton, Massachusetts
Posts: 154
Default

Thank you all for confirming what I already suspected. I believe I have already sourced a local replacement from a 78…now the fun begins.

__________________
1979 Trans Am: Y84 WS6 400/4spd
1967 YS 400, 670 heads, Summit 2802 cam, long tubes, ST-10 trans. McLeod hydraulic clutch conversion.
  #9  
Old 11-18-2023, 10:10 AM
TAKerry TAKerry is offline
Ultimate Warrior
 
Join Date: Feb 2018
Location: North Eastern MD
Posts: 1,148
Default

I was gonna say I have one but not very close.
May be a blessing in disguise. This way you can strip everything down and start new!

  #10  
Old 11-22-2023, 10:21 PM
MDGOAT69's Avatar
MDGOAT69 MDGOAT69 is offline
Senior Member
 
Join Date: Dec 2016
Location: Brockton, Massachusetts
Posts: 154
Default

Quote:
Originally Posted by TAKerry View Post
I was gonna say I have one but not very close.
May be a blessing in disguise. This way you can strip everything down and start new!
I'll definitely be able to do an even more thorough cleaning/painting than I ever anticipated on the bright side haha.

__________________
1979 Trans Am: Y84 WS6 400/4spd
1967 YS 400, 670 heads, Summit 2802 cam, long tubes, ST-10 trans. McLeod hydraulic clutch conversion.
Reply


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

Forum Jump


All times are GMT -4. The time now is 05:50 PM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017