Fox T-Bird/Cougar Forums

Technical => Suspension/Steering => Topic started by: t3skidoo on December 14, 2008, 08:23:44 PM

Title: rear chassis crossbrace
Post by: t3skidoo on December 14, 2008, 08:23:44 PM
My TCs have a chassis crossbrace just in front of the axle, dunno if all Birds/Cats have them or not.

There's a brace on the inside under the carpet that saddles the driveshaft tunnel.  It looks like that inside brace is loose.  Is there anything to reinforcing that brace, welding it solid, and/or replacing it with something else?
Title: rear chassis crossbrace
Post by: daminc on December 14, 2008, 08:32:27 PM
this one?
(http://i233.photobucket.com/albums/ee79/daminc/Cougar%20Pass%20side%20rebuild/IMG_3688.jpg)
Title: rear chassis crossbrace
Post by: t3skidoo on December 14, 2008, 09:20:20 PM
yup, that's it (the inside one, of course)
Title: rear chassis crossbrace
Post by: daminc on December 14, 2008, 09:37:38 PM
You could get a nice piece of 1/8 x 1 steel and replace that if you wanted. or put more bolts in the one you have to tighten it up.
Really comes down to how much more you want to stiffen the car up.
If you aren't worried about twisting the car, just bolt it back in.
Title: rear chassis crossbrace
Post by: t3skidoo on December 14, 2008, 09:51:24 PM
okay, thanks
Title: rear chassis crossbrace
Post by: MasterBlaster on December 15, 2008, 04:31:39 AM
I think the inside strap is mainly a strong mounting point for the studs that go through the floor so the under-brace has something to bolt to. It also helps retain the under-brace in case a u-joint lets go and the brace has to act as a "driveshaft safety loop".
.
Title: rear chassis crossbrace
Post by: daminc on December 15, 2008, 07:42:41 AM
Yea, pretty much all it does.
I'm going to make one that bolts across my crazy SFCs. That will tie them together.
The brace that's under a 3.8 car, doesn't hang down enough for the pipes to go through. I need to change mine anyway, along with the transmission cross member. I may make one of those too.
Title: rear chassis crossbrace
Post by: mark007 on December 15, 2008, 02:33:37 PM
interesting mark vii's have those too. i just pulled all my interior and didnt notice the brace in the car though.
Title: rear chassis crossbrace
Post by: t3skidoo on December 15, 2008, 06:57:27 PM
Quote from: mark007;247625
interesting mark vii's have those too. i just pulled all my interior and didnt notice the brace in the car though.


It might be hard to see if there's a lot of the tar insulation.
Title: rear chassis crossbrace
Post by: t3skidoo on December 16, 2008, 01:05:12 AM
Did some thinking on this.  It would be nice to tie the subframe connectors together instead of relying on the floorpans, but it's also probably a good idea for that brace to be removable. 

How about a tubular bar with a dip in the middle for the exhaust (similar to MasterBlaster's pic) with heim joints at each end, or is there a simpler way?
Title: rear chassis crossbrace
Post by: daminc on December 16, 2008, 07:22:19 AM
What kind of SFCs do you have now?
I'm thinking about bolting my rear brace to them
Title: rear chassis crossbrace
Post by: t3skidoo on December 16, 2008, 10:50:03 AM
The SFCs came from somebody on TF, I think Bob40 is selling them now.
Title: rear chassis crossbrace
Post by: JeremyB on December 16, 2008, 11:14:07 AM
Quote from: t3skidoo;247730
How about a tubular bar with a dip in the middle for the exhaust (similar to MasterBlaster's pic) with heim joints at each end, or is there a simpler way?
Heim joints are not a good choice for something that needs stiffness in bending or torsion. Mounting points like the MM K-member braces are the way to go.
(http://www.maximummotorsports.com/store/images/chass_stiff/MMKB2-2.jpg)

Heim joints are also a bad choice for strut tower braces.
Title: rear chassis crossbrace
Post by: t3skidoo on December 16, 2008, 03:27:58 PM
oh yeah, that looks better and simpler.  weld a couple of tabbecd mounts to the insides of the rails, fab a bar, mount some bolts with bushings in them.
Title: rear chassis crossbrace
Post by: Chuck W on December 16, 2008, 04:15:37 PM
No need for bushings.
Title: rear chassis crossbrace
Post by: t3skidoo on December 16, 2008, 06:41:24 PM
that's even better
Title: Engineering question - how strong are the floorpans
Post by: t3skidoo on December 22, 2008, 02:01:02 PM
Would the brace be more effective if it tied to the SFCS and floor pans, or just the SFCs? 

Which is the better choice?
1) the MM trans crossbrace plus a couple of clevises (a bolt-in solution). 
2) use the factory underside brace as a template to make a longer brace that extends to the SFCs.