C2 Suspension Cross Member

[George C.]

Some will remember last weekend I was having a problem removing the suspension cross member. Thanks to several responses I now have it removed, undercoating scraped off and preparing to paint. I now need to know about the mounting system, mine has a bolt, lock washer, flat washer and a 4 inch plate, then there is a stack of washers to take up the space to the bottom of the cushion. I have checked the service manual and all the drawings in the catologs and have not been able to find any detail to determine if this is correct. Can someone tell me if this is the way it is supposed to be?

Thank you in advance,

George
#36908

[Mike M.]

Re: C2 Suspension Cross Member

george: if you're referring to the rear crossmember that the differential bolts to, then the crossmember is fastened to the frame with the bolt and a lock washer.sounds lioke somone has been there ahead of ya. see assembly manual for details. mike

[George C.]

Re: C2 Suspension Cross Member

Mike,
I checked the assembly manual also, and it only shows a bolt going through the rubber cushion into the "sombrero". That is why I questioned the elaborate mess I have versus what is shown and discussed in the books. I just can't see how the bolt going through a rubber bushing could provide enough support to hold it all together??

George

[Mike M.]

Re: C2 Suspension Cross Member

George: weight of car is what keeps the crossmember and frame mated for all those years. mike

[Joe R.]

Re: C2 Suspension Cross Member

George,

Throw all the flat washers away and mount with the bolt and lock washer. That's the way the general did it.

Regards,

JR

[George C.]

Re: C2 Suspension Cross Member

Mike, JR,

OK, I hate to sound real stupid, but your answers sound like the 4 inch diameter plate, 1/4 inch think, which covers the outside diameter of the mounting cushion is an add on. I also don't see that in the assembly or the service manual. Does that belong there? The cross member is stamped Dana, is that the original?

Thanks again,
George

[Joe L.]

Re: C2 Suspension Cross Member

George-----

The plate and all the other hardware is completely non-original. The only thing that should be there is a 7/16-14 X 1-1/4" bolt and a lockwasher. These go right through the hole in the cemter of the bushing and thread into the weld nut in the center of the "sombrero" bracket. No other parts should be in the assembly.

The crossmember was manufactured by Dana Corporation. However, I've never seen one that was actually stamped "Dana". What is often present is the Dana Corporation "flattened parallelogram" as a manufacturer's ID. I've never seen the word "Dana" in the center of it, though, as it appears on most other Dana-branded products.

GM usually didn't want customers to know who their supplier was for specific components EXCEPT if they were produced by internal, GM divisions (most Corvette components were always "outsourced" and not produced by internal GM divisions of the day). However, GM usually did require that parts carry a "manufacturer's ID". They wanted something that GM could use INTERNALLY to identify the source of a part but something that most customers could not decode. So, the manufacturer's name was rarely found on pieces. When it is found on a few pieces here-and-there, it was usually a mistake. I think that a few manufacturers actually defied the GM policy and put their name on some or all pieces. You won't find much of it, though.

[Mike M.]

Re: C2 Suspension Cross Member

as joe and JR both noted the plate is an add on. BTW, i forgot to mention that since you have the X-member removed, now's a good time to check the welds that fasten the Sombreros to the frame. bout half i'v restored have had some of the weld fractured. now's the time to fix if its broke. mike

[George C.]

Re: C2 Suspension Cross Member

Joe,
Thanks for the detailed info. The crossmember has two flattened and joined parallelograms, one says DANA inside it the other says DETROIT this is on the top of the x-member, it could not be seen unless removed from the car. There is also a number 381 7928. the 381 is on top line 7928 below it.
How bizarre is this the bottom has a small part number 3817927 and the joined parallelograms very small if it says DANA I can't read it without a magnifying glass. The OD of the cushion is about 3 7/8" is that standard size? Also can you tell me what the real part number should be for a 1965?

Thank you,

George

[George C.]

Re: C2 Suspension Cross Member

Mike,
Great idea, I will be cleaning up that are tomorrow, I will check it out. I spent today on the cross member, the drive shaft, the half shafts and the rear end housing and cover. I am tired of the wire wheel and scrapers.

Thanks,

George

[Joe L.]

Re: C2 Suspension Cross Member

George----

The number "3817928" and "3817927" are the part numbers for the upper and lower COMPONENTS of the crossmember. These were welded together to form the assembly. They were never available as seperate parts in SERVICE, though. Basically, these part numbers were for internal use.

For 1965, the complete crossmember assembly, which includes the cushions, was GM #3831589 for early cars and, perhaps, all cars with 327 engine. All cars with L-78 and, possibly, later 327s received GM #3876576.

The difference in the above-referenced crossmembers PRIMARILY relates to the cushions. The cushion used with the 3831589, GM #770447, had a different shell/ retaining tab configuration than the cushion used with the 3876576, GM #9743971. The GM #9743971 cushion became the SERVICE replacement for all 63-65 Corvettes when the GM #770447 was discontinued from SERVICE in October, 1965.

My vague recollection is that the early cushion had wider tabs with spaces between the tabs. The later cushion had slightly narrower tabs which encircled the complete circumference of the cushion with no spaces on the shell between tabs.

[George C.]

Re: C2 Suspension Cross Member

Joe,
Ok now the two different part numbers make sense. The cushions in mine have two tabs on each side, 180 degrees apart from each other. They are about 1/2 inch wide and very close together. The 3 7/8 diameter seemed larger than the new ones I remember seeing. I guess I am off to the Car show at Lowes Speedway in Charlotte tomorrow to pick up some new ones.

Thanks again,

George

[Joe L.]

Re: C2 Suspension Cross Member

George-----

The actual diameter of the "early" and "late" cushions is exactly the same. The "late" style cushions will SERVICE your application, but are not "correct". You can buy replacements of the later style from most of the Corvette parts suppliers like Dr. Rebuild. I doubt that you'll find any of the early style anywhere. Yours may be ok, as-is, though. These cushions usually don't suffer much deterioration and don't need to be routinely replaced.

[Mike Cobine]

Re: C2 Suspension Cross Member

George,
What all the others have missed is that the 4 inch round plate was used to stiffen and support the rear cross member in racing. If you check on more of the car as you go, you may find more hints to a colorful past.

The camber adjustment strut rods were often replaced with Heim joints on each end of a tube to give positive control and adjustment. If they did the cross member bushings, I'm surprised the strut rods haven't been done.

[George C.]

Re: C2 Suspension Cross Member

Mike,
I considered that as a possibility. The only other modification I have found was an offset upper a-frame arm on the right side of the car. The round plates will join the old a-frame arm in the parts that have been replaced box.

Thanks for the response,

George