big block cross member

my69396 · #1 05-03-2008, 10:30 AM

does anyone know the difference or have a picture of a big block 4 speed crossmember as compared to a small block auto cross member? thanks jerry

nuch_ss396 · #2 05-05-2008, 12:00 AM

Jerry,

The small block auto ( 4-speed, Powerglide & THM350 ) crossmember is
the standard crossmember. You will know this one as it has
a race track shaped hole on the underside where the bolts
mount through ( into the trans mount ). The BB THM400
crossmember is of a tubular design ( totally unique ) and the
BB 4-speed crossmember looks similar to the small block
crossmember, however the trans mounting hole is more square-like
with one corner having a protruding tab. Also, the upper
passenger side portion of this same crossmember has a
stamped in recess to clear the speedo cable assy.

Hope that helps.

Nuch

**427TJ** · #3 05-05-2008, 12:36 AM

Plus the trans mount holes in the BB/manual x-member are offset to the passenger side, right? About an inch or so?

nuch_ss396 · #4 05-05-2008, 05:24 AM

Yes Bill - that's correct. Forgot about that.

BEWARE though!

Firebird crossmembers look identical to the BB 4-speed Camaro
crossmembers, but the trans mount holes are in the wrong
location.

There was an auction on ebay a while ago where the
seller showed all the crossmembers in question side-by-side.
I thought I saved it somewhere.....

Nuch

67L78conv · #5 05-05-2008, 06:39 AM

Hope this helps a little. T400 cross member and 4speed BB cross member. Don't have the small block cross member or Firebird one to photograph.

Z28DZ · #6 05-05-2008, 08:40 AM

Here's a thread from the past:

https://www.yenko.net/ubbthreads/showflat...true#Post193331

Allen · #7 05-05-2008, 04:51 PM

Check this out....

http://www.chevynova.org/NovaCrossmember.html

budnate · #8 05-05-2008, 05:00 PM

I did not know the firebird unit was close...how do you keep from picking up the wrong unit at the swap meet???

Allen · #9 05-05-2008, 06:40 PM

[ QUOTE ]
I did not know the firebird unit was close...how do you keep from picking up the wrong unit at the swap meet???

[/ QUOTE ]

Use your calibrated eyes to compare the location of the slots to the edge of the opening. If the slots aren't shifted far enough to the side, it's not the right part.

Lots of them seem to be mis-advertised on Ebay.