Serious Crossmember Problem

uestraven

Daily Driver
Nov 13, 2011
27
0
0
Long Island
I bought a running and driving 1979 Malibu with a 350 and th350 trans but it was originally a v6 car. I looked under the car and noticed the transmission crossmember was rotted to hell so I ripped it out. I bought a stock crossmember for a th350 off ebay and tried to install it but noticed the frame hole did not line up. I bought another xmember to be sure and it did not line up either. What could the problem be?
 

buwagon78

Amateur Racer
Dec 28, 2010
109
0
0
New albany, Indiana
How is the replacement cross member different from the rotted out one? Pics would help if you can post some. It's usually a no brainer.
 

Doober

Moderator
Jun 2, 2003
14,704
1
38
Catalina, AZ
www.cardomain.com
I've never seen a G-Body crossmember NOT line up at the frame, even for different years. Personally I'd say just do what you need to mount it. If the trans MOUNT pad doesn't line up, certain year/engine combos sometimes had an offset pad, my '78 is that way which was a v6 car, my '81 is originally a v8 car which I believe is the reason for the different location.
 

uestraven

Daily Driver
Thread starter
Nov 13, 2011
27
0
0
Long Island
I cant tell if the crossmember is the problem or the car. None of the crossmembers I tried would line up with the bolt holes on the frame. Every one was either too short or too long. Could my car have a different frame?
 

80Grand_LeMans

Dragway Regular
Jun 4, 2008
1,249
0
0
Peabody MA
Im pretty sure it only goes in one way too, have you tried spinning it around? (seems silly, but I've done dumber things lol)
 

Doober

Moderator
Jun 2, 2003
14,704
1
38
Catalina, AZ
www.cardomain.com
Yes, the 'hump' goes on the passenger side, some of the later years with a 2004R used a different crossmember.
crossmember.jpg

This is a TH350 crossmember, note how the holes on the left don't create a line perpendicular to the angle of the crossmember tube itself.

IMAG1049.jpg

This is a 2004R crossmember, note how the holes DO create a perpendicular line, as the crossmember goes almost straight across the frame. To get this crossmember to fit in older (I think '78-'83) cars, an extension would be needed, shown here:
engineswap032.jpg


Some crossmembers (I also believe early years, possibly only v6 I'm not sure) also had 'isolators' to further reduce noise/vibration transmission, they sandwiched on the top/bottom of the ends of the crossmember, the holes are close to 1" in diameter on these crossmembers (or frames, I can't remember for sure) though.
7a67_1.JPG


Going back and looking at pictures of my '78's frame, it appears the large holes are in the crossmember itself.
DSC04596.jpg

DSC04595.jpg
 

uestraven

Daily Driver
Thread starter
Nov 13, 2011
27
0
0
Long Island
Thank you for so much detail in your response, Doober. It really helped. So I looked at every crossmember I had and noticed that the original one that I had ( which is now rotted and unusable) was TH350 xmember. The new ones are both 200 4R xmembers. I guess thats what I get for buying off ebay. I also bought a Jegster 41050 crossmember http://www.jegs.com/i/Jegster/550/41050/10002/-1 but when I tried to install it, the drivers side exhaust hump wouldn't fit under the floor pan.
 

80Grand_LeMans

Dragway Regular
Jun 4, 2008
1,249
0
0
Peabody MA
uestraven said:
Thank you for so much detail in your response, Doober. It really helped. So I looked at every crossmember I had and noticed that the original one that I had ( which is now rotted and unusable) was TH350 xmember. The new ones are both 200 4R xmembers. I guess thats what I get for buying off ebay. I also bought a Jegster 41050 crossmember http://www.jegs.com/i/Jegster/550/41050/10002/-1 but when I tried to install it, the drivers side exhaust hump wouldn't fit under the floor pan.


Hmm :-k I just put the same one in my car and it fit fine. My headers aren't lining up with the exhaust humps though #-o lol
 

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