gary6696

My GM parts book and a couple vendor catalogs say they are the same 63-78.
In the pic, the one on top came from a 66, and the one on the bottom is from some unknown C3. They are identical except the early one bows upward, and the later one bows downward. The dif will sit about 1.5" higher with the one on the bottom.
Does anybody know when they made this change, and what years the one on the bottom fits? Thank you.





[Modified by gary6696, 1:56 AM 2/7/2003]

TCracingCA

I have a 1964 and have upgraded many parts going with the later model parts. I have a later crossmember from a 1975 in my roadster and this is interesting. I will have to think on it. I also liked the little steering arms (tie rod connections) from the later years 75-77 because they were more precision drilled in the exact center, I like the 75-77 3" halfshafts, having no u-bolts but opting for caps, the rear end carrier in a 1964 doesn't have the reinforcing like the big block units and so many changes from part to part year to year that alot of experts just aren't aware of. Thanks, you have peeked my interest and will be watching for an answer. :grouphug: P.S. in how to prepare your corvette for Trans Am racing they recommend raising the differential up to lower the center of gravity or something. I had to install the aluminum body mount bushings to lift everything to help prevent driveline from hitting on the body. I will probably still have to modify the body for clearance. The car is still in the unfinished project stage and hasn't been tested on the road yet with all of my modifications.


[Modified by TCracingCA, 9:31 PM 2/6/2003]

rob75383

I don't have an answer either, but I am also interested.

I think there might be benefits from running a differant cross member, like raising/lowering the center of gravity, and changing the driveshaft angle.

norvalwilhelm

I know that the one on the bottom is like my 75 crossmember. I just had it out.

TCracingCA

Hi, I looked at my original 1964 unit and it bows up in the middle and the 1975 unit also bows upward. They are exactly the same as far as I can tell. In the pictures you have hear it appears the unit on the bottom has like a flange or reinforcement ridge on both sides. The earlier unit only on one side like mine. I wonder if this is out of a 1982 or later do to the different rear axle mounting and design. My guess would it would have to be newer than 1975. Also the older one seems to mount the rear axle higher or closer to the body bowing upward in the middle. I don't have a 1978 or 1982 to look at but am curious. My second thought was that someone put the rubber donut cushions in upside down which I think could happen but then looked at the picture again to see this has to be a later unit or maybe with different transmission automatic and stick they had different lengths so they had to create two different crossmembers for 1975 and on for the driveshaft angle due to the rear and different length of driveshafts or something but then I think the late muncies and th400 had the same lengths so I will have to check. I know that parts varied between small block and big block cars and the later vettes even though down on horsepower options had alot of the big block heavy duty pieces for reliability. I also know in many model years they had early year parts and late year parts with many models of the same years having assembly line variations. Who knows! I hope someone gets us an answer. I will keep looking and now can't wait to climb underneath everyones cars at the next Pomona car swap meet to check out crossmembers. :cheers:


[Modified by TCracingCA, 3:40 AM 2/9/2003]