68-72 removable front X member ???

[Geoff C.]

[Joe L.]

Re: 68-72 removable front X member ???

Geoffrey------

The forward bolts go "down" and the rear bolts go "up", as you described your observations of your 68s and 69.

Several different u-braces and several different cross members were used over the 68-69 period. However, I don't think that the orientation of the bolts changed with any of the parts.

My original owner, September, 1969-built convertible is configured as above.

[Geoff C.]

Joe and I must have the only 68 & 69's here

Joe,
Thanks for confirming my belief.
Geoffrey

[John A.]

Re: Joe and I must have the only 68 & 69's here

Geoffrey & Joe,

My 69 also has a four-up bolt configuration. I have always wondered if this config was original to the car. The NOS replacement and the repo replacement cross member I checked out have the two-up / two-down configuration. This makes replacing any bent components difficult because a pair match is needed. Don't know if it makes any difference, but this car has a Jan 69 build date.

[Joe L.]

Re: Joe and I must have the only 68 & 69's here

John-----

If you can, check the configuration of the u-shaped bumper bracket on your car. For your 4 bolt "up" configuration to be original, there should be 4 weld nuts on the bracket flange. Also, there should be NO weld nuts on the crossmember if there are 4 weld nuts on the bracket.

Although it was a 1969+ PRODUCTION part, crossmember GM #3954506, was the GM-catalogued SERVICE part for all 68-72 Corvettes. If the crossmember had 2 weld nuts attached to the center bolt holes (for the u-bracket) and if the 68 and/or early 69 applications used 4 "up" attaching bolts, then the 3954506 crossmember could not have serviced the 68 and/or early 69 application without removal of the weld nuts from either the crossmember or the u-bracket. Chevrolet specified no such modifications required for installation of the 3954506 cross member for 68 and/or early 69 applications.

[John A.]

[Mike Baker]

Re: Joe and I must have the only 68 & 69's here

My 68 also has the bolts in a "four up" configuration. However, I do know that the nose was damaged at some time in it's life, so I cannot vouch for the originality of the bracket or crossmember.

All four of the nuts are welded to the bracket, and John I do not see the other holes in the crossmember that you described in you post.

I doubt that my post really helps much but I thought I would contribute my observation.

[Geoff C.]

[Joe L.]

Re: Humble Pie and 68-72 Cross Members

Geoffrey-----

OK, I THINK that I might have it figured out now. But, I've got to admit, this thing was a REAL challenge.

As it turns out, there WERE 4 different u-brackets and there WERE 3 different crossmembers. Here's what I found:

1) the original u-bracket used for 1968 Corvettes was GM #3914260. This, apparently, is the bracket with 4 weld nuts for the "4-up" configuration. This bracket may or may not have been used for all of 1968 PRODUCTION and/or it may or may not have been used for early 1969 PRODUCTION. I figure the model year changeover "syndrome" may apply here. The GM #3914260 bracket was discontinued from SERVICE in October, 1969 and replaced by the GM #3980824 bracket

2) the original cross member used for 1968 Corvettes was GM #3915769. This is likely the crossmember with NO weld nuts and is used with the 3914260 bracket. It's period of use in PRODUCTION is not known to me. It was discontinued from SERVICE and replaced by the GM #3935593 in October, 1968. It may have been used in PRODUCTION throughout the 1968 model year or it may have been replaced by the GM #3935593 sometime during the the later part of the model year. The GM #3935593 was discontinued from SERVICE in May, 1969 and replaced by the GM #3954506. I expect that both the 3915769 crossmember and the 3935593 crossmember are configured alike with respect to the absence of weld nuts for the bracket attachment;

3) I question whether the GM #3938080 u-bracket was ever actually used during the 1968 model year, regardless of what the AIM says. I think that this bracket is the one with 2 weld nuts and 2 holes for the "2-up, 2-down" bolt configuration and was used for the 1969 model year. The GM #3938080 bracket was NEVER available in SERVICE. This bracket was likely the one set up only for the 68-68 style grilles/bumperettes;

4) I think that the GM #3963129 bracket used in PRODUCTION for the 70-72 model years has the same weld nut configuration as the 3938080. However, I expect the difference is the accomodation for the 70-72 style grilles/bumperettes. The GM #3963129 bracket was NEVER available in SERVICE, either. Only the SERVICE-only GM #3980824 bracket was available for all 69-72 SERVICE requirements.

The only thing that all of the above does not answer is how the GM #3980824 bracket could have replaced the GM #3914260 for SERRVICE of 1968 models OR how the GM #3954506 crossmember could have replaced the GM #3935593 for SERVICE of 1968 models. However, here are some possibilities:

a) The 3980824 bracket could have been used to replace the 3914260 if the 3980824 had used 2 weld nuts AND the user added two conventional nuts to secure the other 2 bolts used in the 68 configuration; in the 69-72 configuration, the bracket would be used as-is. Or, the 3980824 might have had NO weld nuts and conventional nuts were to be used by the customer for all 4 positions. The weld nuts are a convenience in PRODUCTION that GM might not have felt was so necessary in SERVICE;

b) I cannot come up with any way that the 3954506 cross member with 2 holes and 2 weld nuts could have been used to SERVICE the 68 application IF the u-brace was not changed at the same time. But, I KNOW that GM DID specify the 3954506 to replace the 39355593 for SERVICE of 1968 models.

I can also report that I have checked a friend's original owner, early build 1969 which I KNOW to be original. His car was built in October, 1968 and he has the "2-up, 2-down" bolt configuration. As I stated previouly, my original owner late-build 1969 has the "2-up, 2-down" configuration, too.

Incredibly enough, I do not have a known example (with GM parts tag) of either the GM #3980824 bracket or the GM #3954506 crossmember. This is a deficiency that I hope to remedy when I get a chance. However, might you have examples of either of these in your inventory to refer to?

[John A.]

Re: Humble Pie and 68-72 Cross Members

Geoffery,

This has turned out to be a novel of a tale... But following through with regard to your question...

The VIN of my 69 is 12027... Also, the drain holes you referred to... I believe are actually access holes for the two bolts that attach to the radiator support.

As I mentioned, my car has had front end repairs, but doubt that these two pieces were ever replaced - they both show signs of minor stress at the bolt holes and are not perfectly straight. When Buba was making repairs back in the 80's I'm sure that service replacements would have been easy to find. It was easier to just straighten the original as best as possible to save money.

From your information and Joe's explanation - it appears that almost anything is possible!

...Also... did you say you sent me a nasty letter?

[Geoff C.]

[Jim T.]

Re: 68-72 removable front X member ???

On my original owner Feb built 68 the two bolts in front are placed down in a caged nut on the crossmember and rear come from under the crossmember into the u-shaped brace. This crossmember does not have the additional holes that were mentioned. My 70's U-shaped brace attaches the same way but the crossmember does have the two additional holes which two bolts are used to secure the radiator support at the bottom.

[Geoff C.]

Re: Humble Pie and 68-72 Cross Members

Joe,
I has some NEW GM big U braces up until about 2 years ago and cannot recall the weld nut configuration. It has been a very long time since I have has a New GM x-member.
Geoffrey

PS I'm still confused if you look at the VIN's on my 3 cars, yours, yor buddys and John Andre's - the succession of arrangements or evolution is redundant at best.

[Geoff C.]

Above HAS should be HAD; I can't type well *NM*

[Shannon Burgess]

Re: Joe and I must have the only 68 & 69's here

I'm chiming in late here, but my April '69 build date car has the 2 up / 2 down setup. Seems strange that they would have switched back and forth during production.

Shannon