TB2 - Technical Bulletin 2

Subframe Strengthening 

The Holden HQ-HZ subframe has two open channel sections that run down each side of the vehicle. The gearbox support panel ties the two channels together at the lower edges with two bolts at each end. 

The gearbox support panel is discarded when fitting the subframe to the Cheetah centre section.
  
It is recommended a 1/8th (3.2mm) plate is welded to the inside of each open channel section to box them in, similar to a ute chassis.
 
The plate size is 34.25” (870mm) x 2.56” (65mm) x 1/8th (3.2mm) thick. 
Make sure the channel sections are parallel to each other before welding.  Ensure a good weld is made at the front edge where the plate contacts the subframe as this is where most of the strength is imparted.   
 
It is suggested the brake line, fuel lines and brake bias valve located inside the right hand side channel are run on the outside of the plate. 

Because of limited space when the subframe is in position, it is suggested either a later model brake bias valve/brake line splitter assembly is used, moving the existing valve to another position or cutting a suitable slot in the plate to allow clearance. 

HQ subframe showing plate welded to the LH channel section.
HQ subframe detailing front edge weld of plate to subframe